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2000 American College of NeuropsychopharmacologyPublished by Elsevier Science Inc. 0893-133X/00/$see front matter655 Avenue of the Americas, New York, NY 10010 PII S0893-133X(99)00147-5

Naltrexone Alters Subjective and PsychomotorResponses to Alcohol in HeavyDrinking Subjects

Mary E. McCaul, Ph.D.,

Gary S. Wand, M.D., Thomas Eissenberg, Ph.D

.

,Charles A. Rohde, Ph.D.

,

and Lawrence J. Cheskin, M.D.

Preclinical studies support endogenous opioid systeminvolvement in alcohol reinforcement and consumption;however, recent clinical trials and human laboratory studieshave provided mixed findings of the effects of naltrexone (anon-selective opioid antagonist) on alcohol responses. Thisstudy used a within-subject design (

n

23) to investigatenaltrexone effects (0, 50 and 100 mg qd) on subjective andpsychomotor responses to alcohol (none, moderate, high) inheavy drinkers. Before alcohol administration, subjectsreported decreased desire to drink alcohol when maintainedon 50 mg compared with placebo naltrexone. Followingalcohol administration, active naltrexone significantlyincreased subjective ratings of sedative, and unpleasant/sick

effects and decreased ratings of liking, best effects and desireto drink. Naltrexone generally did not alter subjective orobjective indicators of drunkenness. Finally, high doses ofnaltrexone and alcohol interacted to produce the greatestdecreases in liking and best effects. Findings support therole of endogenous opioids as determinants of alcoholseffects and suggest that naltrexone may be particularlyclinically useful in those treatment patients who continue todrink heavily.

[Neuropsychopharmacology 22:480492,2000]

2000 American College ofNeuropsychopharmacology. Published by ElsevierScience Inc.

KEY

WORDS

:Alcoholism; Naltrexone; Opioid; Subjectiveresponses; Psychomotor responses

Over the last decade, preclinical and clinical researchhave convincingly demonstrated the involvement ofthe endogenous opioid system in alcohol reinforcementand consumption. First, it is clear that opioid agonistand antagonist administration alters alcohol consump-

tion (Czirr et al. 1987; Hubbell et al. 1986; Reid et al.1991). For example, animal studies have demonstratedslowed acquisition of alcohol self-administration (Phil-lips et al. 1997) and decreased alcohol consumption fol-lowing administration of the non-selective opioid re-ceptor antagonists naloxone (Froehlich et al. 1990;Hubbell et al. 1986; Hyytia and Sinclair 1993 ; Reid et al.

1991; Weiss et al. 1990), naltrexone (Altshuler et al.1980; Boyle et al. 1998; Davidson and Amit 1997 ; Myerset al. 1986; Reid et al. 1996; Volpicelli et al. 1986), andnalmefene (Hubbell et al. 1991). The second line of evi-dence for functional involvement of the opioid systemin mediating alcohol drinking behavior comes fromneurobiological studies which indicate that alcohol al-ters opioid peptide systems. Acute alcohol administra-tion increases endorphin and enkephalin gene expres-sion in discrete brain regions of rodents, increasesopioid peptide release from both brain and pituitary of

From the Johns Hopkins University School of Medicine (MEM,GSW, LJC), Virginia Commonwealth University (TE), Richmond,Virginia; and Johns Hopkins University School of Public Health(CAR), Baltimore, Maryland.

Address correspondence to: Mary E. McCaul, Ph.D., Departmentof Psychiatry and Behavioral Sciences, Johns Hopkins UniversitySchool of Medicine, 911 N. Broadway, Baltimore, MD 21205. Tel.:410-955-5439; Fax: 410-955-4769.

Received December 30, 1998; revised October 25, 1999; acceptedNovember 5, 1999.


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rodents in vitro

, and increases opioid peptide releasefrom the pituitary of rodents and humans in vivo

(Gi-anoulakis 1990 ; Gianoulakis et al. 1996; Li et al. 1996).The third line of evidence for functional involvement ofthe opioid system in mediating alcohol drinking behav-ior is derived from genetic studies which indicate that a

genetic predisposition toward alcohol drinking is ac-companied by altered responsiveness of the opioid sys-tem at baseline and in the presence of alcohol in bothrodents and humans (Gianoulakis et al. 1996; Krishnan-Sarin et al. 1995; Li et al. 1996; Wand et al. 1998). Forinstance, alcohol consumption induces a more robustincrease in plasma beta-endorphin in subjects with apositive family history of alcoholism compared to fam-ily history negative subjects (Gianoulakis et al. 1996).

These findings involving the endogenous opioid sys-tem in alcoholism have led to several recent clinical tri-als examining the effectiveness of opioid antagonists for

the treatment of recently abstinent alcohol-dependentsubjects. Two 12-week, double-blind clinical trials(OMalley et al. 1992; Volpicelli et al. 1992) reported theeffectiveness of naltrexone in combination with psycho-social treatment participation in decreasing relapse andalcohol drinking days. Most striking was a reduction offull-blown relapse (consumption of five or more drinksper occasion) among those patients who resumeddrinking, with the risk of relapse among placebo-treated patients approximately twice that of naltrexone-treated patients. Findings suggest that the effectivenessof naltrexone in preventing alcohol relapse may stemfrom a decrease in the subjective experience of alcohol

high or intoxication following alcohol consumptionamong naltrexone-treated compared to placebo-treatedpatients (OMalley et al. 1996; Volpicelli et al. 1995);however, these findings are confounded by lower levelsof alcohol consumption per drinking episode amongnaltrexone patients.

Human behavioral pharmacology laboratory studiescan provide sensitive tests of potential pharmacothera-pies for persons with alcohol or drug use disorders.Generally, the interaction of a given medication with itstarget drug is more easily detected in the laboratorythan in the clinic (Bigelow and Walsh 1998); however,

to date, findings of human laboratory research examin-ing the interaction of naltrexone and alcohol have beenequivocal. Doty and colleagues (Doty and de Wit 1995 ;Doty et al. 1997) have reported no effects of naltrexonepretreatment (25 or 50 mg) on subjective responses fol-lowing a range of alcohol doses (placebo, 0.25 g/kg,0.50 g/kg, 0.75 g/kg) in social drinkers. In contrast,Swift and colleagues (Swift et al. 1994) observed re-duced stimulant effects and increased sedative effectsof alcohol following acute naltrexone (50 mg) as com-pared with placebo administration in social drinkers.Also, chronic naltrexone administration (50 mg) has

been reported to increase latency to drink alcohol in so-

cial drinkers in a naturalistic bar setting, although nodifferences were observed in self-reported urge to drinkor liking, stimulant or sedative effects, number ofdrinks ordered, or latency to finish the beverage(Davidson and Amit 1997). Finally, recent findings havesuggested the potential role of family history of alcohol-

ism as a determinant of naltrexone effects on alcohol re-sponses (King et al. 1997). Naltrexone (50 mg) de-creased alcohols stimulant effects on the rising BALlimb in family history positive (FHP) but not family his-tory negative subjects. In both family history groups,naltrexone decreased vigor and increased fatigue, ten-sion and confusion scores on the Profile of Mood States,with FHP subjects evidencing increased confusion onthe ascending BAL limb following naltrexone.

The present human laboratory study has a numberof design strengths. First, this project used a completelywithin-subject design, thus maximizing statistical sensi-

tivity. Second, a range of naltrexone doses (0, 50 and100 mg qd) were examined under chronic dosing proce-dures. Within each naltrexone dose condition, a rangeof alcohol doses (no, moderate and high) were studied.This dosing procedure allowed for the examination of

both direct and interactive effects of alcohol and nal-trexone on responses. Finally, a broad spectrum of mea-sures including subjective and psychomotor responseswere obtained repeatedly before and for an extendedperiod after alcohol ingestion within each session, al-lowing in-depth assessment of time course of effects.

METHODS

Subjects

Potential study participants (N

99) were recruitedwith newspaper advertisements and word of mouth.Persons aged 2560 with moderate to heavy alcohol use(an average of five drinks per occasion or five drinkingdays per week), low levels of associated problems(MAST score

5; (Selzer 1971), and no acute or chronichealth problems were eligible to participate in a clinicalinterview and medical examination to determine studyeligibility. Exclusion criteria included: current use of

any prescription medication, chronic health problems,liver enzyme levels over twice normal limits, preg-nancy, a major Axis I diagnosis on the Structured Clini-cal Interview for DSM-IIIR (Spitzer and Williams 1987),including alcohol or drug abuse/dependence. Seventy-two individuals were determined to be ineligible forstudy participation due to a diagnosis of alcohol abuse/dependence and/or medical or psychiatric exclusions.

Twenty-seven subjects participated in one or moresessions of the laboratory study. Of these, four weresubsequently excluded from data analysis: one waswithdrawn from the study prematurely due to healthconcerns unrelated to study medication, one subject


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had excessive missing data, and two were disqualifieddue to illicit drug use detected during routine urinescreening prior to study sessions.

Table 1 summarizes the demographic and substanceuse characteristics of the twenty-three subjects whosedata are presented in the present report. Four were fe-

male and 11 were of minority ethnic/racial status. Sub-jects averaged 37 years old and all subjects had a highschool education or greater. Two-thirds were employedat the time of their research participation and almost allhad either never been married or were separated or di-vorced. Subjects reported drinking an average of almostfive standard drinks per drinking occasion, consumedalcohol on an average of 13 days per month, and had

been drinking alcohol for an average of 19 years.Slightly more than half of the subjects smoked tobaccocigarettes and they averaged about three-quarters of apack per day. Almost half reported occasional mari-

juana use and a quarter of the sample also used cocaineoccasionally.Subjects were informed that the study was intended

to determine how drugs from different pharmacologicclasses modify alcohols effects. All potential subjectssigned an institution-approved informed consent docu-ment prior to any research participation and were paidfor their time in the study.

Procedures

During their first visit, subjects participated in the clini-cal interview and medical screen. Eligible subjects then

received massed practice of ten trials on each of the

psychomotor tasks (described below) to attain a stableperformance baseline prior to starting the experiment.Subjective report items also were reviewed to familiar-ize subjects with these measures.

All study sessions were conducted at the GeneralClinical Research Center (GCRC) at the Johns Hopkins

Bayview Medical Center. Subjects participated in theresearch over a 6-week period. Each of three naltrexonedoses was administered over an 8-day inpatient stay onthe GCRC. There was a one-week outpatient wash-outperiod between each naltrexone dose period.

Within each naltrexone dose, GCRC admission wason Friday; the naltrexone dose scheduled for that weekwas administered daily at 8 pm for 7 days starting onthe day of admission. Over the course of the 8-day inpa-tient stay, subjects participated in alcohol challenge ses-sions on Monday, Wednesday and Friday. Subjectswere discharged from the GCRC on Saturday morning.

On each alcohol challenge session day, subjects wereprovided with a standard (no caffeine) breakfast at 7:30

A

.

M

. and a snack at 10:00 A

.

M

.. Neither cigarette smok-ing nor additional food or drink were permitted be-tween 10:00 A

.

M

. and 3:30 P

.

M

.. Sessions began with theinsertion of a heparinized catheter in a non-dominantforearm vein approximately 90 minutes prior to alcoholadministration. Subjects remained in a quiet room dur-ing testing, and remained seated except as required forperformance measures.

Drug Preparation and Administration

All subjects participated in nine sessions according to acompletely within-subject, randomized block design.Each subject received the three naltrexone dose condi-tions (0, 50 and 100 mg po) in random order. Each dailynaltrexone dose was prepackaged and individually la-

beled and dated using 50 mg naltrexone tablets andmatching placebo (DuPont Pharma). Subjects ingestednaltrexone under observation by the GCRC nursingstaff at 8 p.m. daily.

Each of the three alcohol dose conditions (no, moder-ate, high) was presented in random order within each

naltrexone dose condition. Alcohol drinks were pre-pared by mixing the appropriate amount of pure etha-nol (minus 3 ml which was added just prior to adminis-tration, see below) with juice to a volume of 16 ounces.The drink was separated into three equal amounts; sub-

jects had five minutes to drink each glass (McCaul et al.1990). In this report, time 0 and alcohol administra-tion both refer to the end of this 15-minute administra-tion procedure. In order to conceal the alcohol contentof the drink, a wrist band soaked in ethanol was placedaround the glass to deliver an alcohol odor and 1 ml ofethanol was floated on top of each glass to deliver anethanol taste. Alcohol dose levels were 0.0, 0.6 and 1.2

Table 1.

Demographic and Recent Substance UseCharacteristics (N

23)

Characteristics Mean

SD Range

Age (yrs) 38.3 (7.7) 28.555.5Education (yrs) 13.1 (2.5) 1020Females (%) 17Race/ethnicity (%):

White 48African-American 48

Hispanic 4Employed (%) 65Marital status (%)

Never 58Married 4Separated/divorced 48

Alcohol use:Drinks/occasion 4.6 (2.0) 310Days/month 12.0 (4.0) 622Years of use 19.7 (7.4) 733

Tobacco use:% Smokers 57Cigarettes/day 15.2 (5.4) 620

Marijuana users (%) 39Cocaine users (%) 26


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g/kg for the first four subjects to complete the study.Dose levels were reduced to 0.0, 0.5 and 1.0 g/kg for theremainder of the study participants due to excessive in-toxication following the initial high alcohol dose level.For analysis, these dose conditions have been combinedinto no, moderate and high alcohol doses. GCRC

nurses, the study research assistant and subjects wereblind to all ethanol and naltrexone doses.

Dependent Measures

During each alcohol challenge session, subjects partici-pated in repeated administrations of a comprehensivetest battery that included subjective reports, autonomicdata collection, a blood draw through the indwellingcatheter and performance tasks in this order. Relative toalcohol administration (time 0), blood samples for neu-roendocrine and blood alcohol determinations were

drawn at -30, -15, 0, 15, 30, 60, 90, 120, 150 and 180 min-utes. Recordings of heart rate, blood pressure, skin tem-perature and conductance began 60 minutes prior to al-cohol administration and were continuous until 180minutes after alcohol administration. Subjective andperformance measures were obtained at -60, 0, 15,30,60, 90, 120, 150, 180, 240, 300, 360, 420, and 480 min-utes. Neuroendocrine and physiological measures arenot included in the present report.

Subjective measures

were displayed using an AppleIIE microcomputer and completed by subjects using a

joystick that moved a cursor on the screen to mark theappropriate response. Measures included visual analog

scales (VAS), the Subjective High Assessment Scale(SHAS) (Schuckit 1980), and the short-form of the Ad-diction Research Center Inventory (ARCI; (Haertzen1974). The visual analog scales used a horizontal lineanchored with Not at all on the left and Extremelyon the right. The four VAS items included the ques-tions: How high do you feel right now?, How sleepydo you feel?, How badly would you like an alcoholdrink right now?, and How do you like the effects ofthe capsule/beverage you received?

The Subjective High Assessment Scale consists of fif-teen brief descriptors of alcohol effects, including un-

comfortable, high, clumsy, muddled or confused,slurred speech, dizzy, nauseated, drunk or intoxicated,sleepy, distorted sense of time, effects of alcohol ordrug, difficulty concentrating, feelings of floating, theworst Ive ever felt, and the best Ive ever felt. Subjectswere instructed to respond for how they felt rightnow using a horizontal line anchored by Normal onthe left and Extremely on the right.

The short-form of the Pentobarbitol-Chlorprom-azine-Alcohol Group (PCAG) subscale of the AddictionResearch Inventory consisted of 15 items sensitive tosedative drug effects.

Performance measures

consisted of a balance measure,

a reaction time task and two tests of memory. Balancewas measured by asking subjects to stand upright onone foot with eyes closed and arms extended to the sideat shoulder height. Each trial lasted 30 seconds or untilthe subject touched the raised foot to the ground. Sub-

jects completed two trials on each foot during each data

collection period, thus the maximum score was 60 sec-onds measured separately for the right and left foot.

Reaction time was assessed using the circular lightsapparatus which consists of 16 lights illuminated inrandom order and arranged circularly around a 54-cmdiameter. When a button adjacent to each light waspressed, the light extinguished and the next bulb waslit. Reaction time was determined by the number oflights that subjects extinguished in a 60-second period.

The computerized version of the Digit-Symbol Sub-stitution Test is described elsewhere (McLeod et al.1982). In response to random digits (19) that appeared

in the center of the video screen, subjects pressed but-ton positions on a numeric keypad to reproduce thegeometric pattern associated with that digit by usingthe digit-symbol code displayed continuously at the topof the video screen. The scores were the number at-tempted and the number of correct substitutions duringa 90-sec trial.

A computerized numeric recall task assessed short-term memory. During each trial, an 8-digit number wasdisplayed on the computer screen. First, subjects en-tered the number while it was still displayed on thescreen. If a subject entered the number incorrectly whileit was still displayed, the trial was discontinued and a

different 8-digit number was presented. If the subjectentered the number correctly, the number then disap-peared from the screen and, either immediately (5 tri-als) or after a 8-second delay (five trials), subjects en-tered the number from memory. The task continueduntil the subject had correctly entered ten 8-digit num-

bers during the first component of the task or 25 incor-rect attempts were made. Scores included the totalnumber of trials attempted and the number of digitscorrectly reproduced during the recall component ofthe task.

Data Analysis

Statistical analysis was performed using STATA 5.0 andits GEE module. Analyses were based on a longitudinalanalysis with subject as a random effect. Variables in-cluded alcohol dose, naltrexone dose and time. For eachmeasure, baseline levels were first examined as a func-tion of alcohol and naltrexone dose levels. When signif-icant baseline effects were observed, baseline values ofthe variable were entered as covariates in subsequentanalyses. Initial analyses examined the independentand interaction effects of each active alcohol and nal-trexone dose compared to placebo. When the interac-


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tions were not significant, the final model was simpli-fied to examine only the independent effects of alcoholand naltrexone. For each response variable, the tradi-tional significance level ofp

.05 was adjusted usingBonferronis method top

.01 to compensate for analy-ses examining two main effects of alcohol, two main ef-

fects of naltrexone, and time. Significance levels for alco-hol X naltrexone interactions were set at p

.05 sincethese interactions were the primary scientific focus of theresearch.

RESULTS

Subjective Effects

Desire to Drink. At baseline prior to alcohol adminis-tration, subjects maintained on 50 mg naltrexone re-ported a decreased desire to drink alcohol compared to

subjects maintained on placebo naltrexone (

p

.01).There also was a trend for decreased desire to drink atbaseline for the 100 mg compared to placebo naltrexonecondition (

p

.10). There was a significant effect ofbaseline ratings of desire to drink on ratings followingalcohol administration (

p

.001); that is, the higher asubjects baseline report, the higher the subjects post-ingestion rating.

Ingestion of the moderate or high alcohol dose didnot alter desire to drink when subjects were maintainedon placebo naltrexone. In contrast, subjects maintainedon 100 mg naltrexone reported significantly less desireto drink following alcohol administration compared toplacebo naltrexone (Table 2). The moderate dose of nal-

trexone did not affect self-reported desire to drink fol-lowing alcohol administration.

Active compared to placebo naltrexone disrupted al-cohol consumption during the drink ingestion period.During at least one of their nine sessions, twelve of the23 subjects either refused to drink a portion of the alco-hol beverage (N

5) and/or drank the beverage at aslower pace than the 15-minute study procedure al-lowed (N

9; X

27 minutes; range: 2045 minutes).Eleven of the 12 subjects experienced the first disrup-tion of their alcohol ingestion during an active naltrex-one session and only one subject during a placebo nal-

trexone session (Z

5.21 ,p

.0001).

Best/Like Effects. All three alcohol doses increasedsubjects reports of like effects of capsule/beverageand best Ive ever felt over baseline responses prior todrink ingestion. Subjects analog ratings of like effectswere comparable across the three alcohol doses. Sub-

jects reports of best Ive ever felt were somewhat

Table 2.

Separate and Interactive Effects of Naltrexone and Alcohol on Subjective Responses. Arrows IndicateDirection of Effect

Subjective Effects Nx 0 vs 50 Nx 0 vs 100 Alc 0 vs Mod Alc 0 vs High Interactions

DESIRE TO DRINK

b

BEST

c

c

5

0

a

, 100

b

LIKING

c

5

0

a

, 100

a

Sick/unpleasant effectsUncomfortable

c

b

c

c

Nauseated

c

c

c

c

Worst Ive felt

c

c

c

Sedative effectsClumsy

b

c

c

c

Confused

b

c

c

c

Slurred speech

b

c

c

Sleepy b c c

Trouble concentrate b c c

Floating c c 100aDizzy c b c c

Time distorted b c c 100b, 100b

PCAG SCALE c c 100b

High/intoxicatedHigh c c 50a

Drunk c c

Feel effects b c c

ap .05.bp .01.cp .001.Mmoderate alcohol doseH high alcohol dose50 naltrexone 50 mg100 naltrexone 100 mg


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lower following the moderate alcohol dose in compari-son to high dose or placebo alcohol.

There was a main effect of 50 mg naltrexone on theitems of like effects (p .01) and best (p .001). Inall three alcohol conditions, subjects on 50 mg naltrex-one reported significantly lower best and like effects

compared to responses in the placebo naltrexone condi-tion. There was an interaction of the high doses of nal-trexone and alcohol on the two subjective measures ofbest Ive ever felt (p .01) and like effects of cap-sule/beverage (p .05). Specifically, the combinationof naltrexone 100 mg and the high alcohol dose de-creased ratings on these response items more than ex-pected based on the separate effects of either drug. Asshown in Figure 1A, naltrexone 50 mg lowered reportsof liking by 13% and naltrexone 100 mg lowered reportsof liking by 25% across the entire post-ingestion period.Reports of best effects were dampened 5% and 23% by

the moderate and high naltrexone doses, respectively(Figure 1B). Interestingly, the temporal pattern of responsedampening was somewhat different for best and like ef-fects (Figure 1). In the 100 mg naltrexone condition, themaximal reduction of liking was approximately 50%and occurred in the second half of the 8-hour session. Incontrast, the maximal reduction in best effects occuredearly after drink ingestion during the first two hours ofthe eight hour session.

Sick/Unpleasant Effects. At baseline prior to alcoholadministration, reports of nausea were modestly de-creased in the two active naltrexone conditions relative

to placebo naltrexone (both p .05). Alcohol adminis-tration produced dose-dependent increases in unpleas-ant effects of alcohol, including uncomfortable, nause-ated, and worst Ive ever felt (Table 2). Theseunpleasant effects decreased gradually across the post-ingestion period (all time effects,p .001). There was asignificant effect of baseline ratings of nausea on ratingsfollowing alcohol administration (p .001), such thatthe higher a subjects baseline report, the higher thesubjects post-ingestion rating of nausea.

As shown in Figure 2, alcohol administration in-duced higher levels of nausea when subjects were

maintained on active compared to placebo naltrexone.Following the moderate alcohol dose (Figure 2A), self-reports of nausea averaged across the post-ingestionperiod were unchanged for subjects on 50 mg naltrex-one and increased 14% for subjects on 100 mg naltrex-one compared to placebo naltrexone. Nausea ratingsfollowing the high alcohol dose (Figure 2B) were in-creased 22% and 7% for subjects on 50 mg and 100 mgnaltrexone, respectively. These subjective ratings of sickeffects were paralleled by increased rates of vomitingfollowing alcohol administration when subjects wereon active naltrexone. There were eight episodes of vom-iting during sessions, seven during alcohol sessions

when subjects were on active naltrexone and one onplacebo naltrexone (Z -3.21,p .001). Generally, thevomiting occured well after the drink administrationperiod, around two to three hours post-ingestion.

Sedative Effects. Alcohol administration increased a

variety of sedative response items (Table 2). For allmeasures except sleepy, alcohol effects on sedation de-creased gradually across the post-ingestion period (alltime effects, p .001). Scores on the PCAG (sedative)scale of the Addiction Research Center Inventory alsowere significantly increased following administrationof moderate and high doses of alcohol.

Generally, sedative effects were increased in the ac-tive compared to placebo naltrexone conditions. Thesesedative effects of naltrexone were observed on agreater number of response items when subjects weremaintained on the high compared to moderate dose ofnaltrexone (Table 2). However, significant interactionsof high dose naltrexone and alcohol were observed onthe sedative response items of floating, time distortionand PCAG scale scores such that subjects reported lesssedation following the combination of alcohol and highdose naltrexone than would have been predicted bytheir separate effects.

High/Intoxication. Alcohol ingestion significantly in-creased self-reports of intoxication, including high,drunk and feel effects of alcohol or drugs (Table 2).These effects decreased gradually across the post-inges-tion period (all time effects, p .001). Naltrexone did

not alter these measures of alcohol-related intoxication.

Psychomotor Effects

Stance Stability. In the absence of alcohol, there wasa small but significant decrease in stance stability/leftfoot when subjects were maintained on the 50 mg com-pared with placebo naltrexone (p .01). In general, al-cohol ingestion impaired stance stability (Table 3).There were no systematic effects of naltrexone on stancestability following alcohol ingestion.

Reaction Time. In the absence of alcohol, there was asmall but significant decrement in circular lights perfor-mance when subjects were maintained on 100 mg(Mean lights extinguished 106.6) compared to pla-cebo naltrexone (Mean lights extinguished 109.4)(p .01).

Circular lights performance was significantly de-creased by the moderate and high dose of alcohol (Ta-

ble 3). As shown in Figure 3, there were significant ef-fects of 50 mg and 100 mg naltrexone on reaction timeas measured by circular lights performance, with 100mg naltrexone producing significantly greater impair-ment than 50 mg naltrexone (Table 3). This effect of nal-


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Figure 1. Analog scores for liking of the capsule/beverage (A) and best Ive ever felt (B) prior to and following thehigh alcohol dose as a function of naltrexone dose condition. Symbols indicate means across subjects in each dose conditionat each time point. Symbols to the left of the 0 time point represent baseline scores prior to alcohol administration. Naltrex-one doses include placebo (), 50 mg ( ), and 100 mg ( ). Liking was scored on an analog scale from 0 (not at all) to 39(extremely). Best Ive ever felt was scored on an analog scale from 0 (normal) to 9 (extremely).


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trexone on circular lights performance was primarilyobserved following the moderate dose of alcohol (Fig-ure 3A). Across conditions, performance recoveredover the 8 hour post-ingestion period (time;p .0001).

Memory. At baseline in the absence of alcohol, therewere no effects of naltrexone on memory as measured byDSST and recall performance. Ingestion of the high alco-hol dose produced significant decrements in the number

Figure 2. Analog scores for nauseated prior to and following the moderate (A) and high alcohol dose (B) as a function ofnaltrexone dose condition. Symbols indicate means across subjects in each dose condition at each time point. Symbols to theleft of the 0 time point represent baseline scores prior to alcohol administration. Naltrexone doses include placebo (), 50 mg(), and 100 mg ( ). Nauseated was scored on an analog scale from 0 (normal) to 9 (extremely).


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of attempted and correct DSST responses, with a trendtowards lower numeric recall scores (p .02) (Table 3).

As shown in Table 3, there was significant improve-ment in DSST performance when subjects received 100mg naltrexone. This effect appeared to be largely the re-sult of improved performance for subjects on 100 mgnaltrexone in the placebo alcohol condition. Specifi-cally, following placebo alcohol administration, sub-

jects on 100 mg naltrexone attempted significantly moreDSST items (p .007) and tended to get more items cor-rect (p .03) compared to placebo naltrexone. Thisimprovement in performance did not occur when sub-

jects on 100 mg naltrexone received active alcohol.Following active alcohol administration, DSST per-formance was comparable across the naltrexone dosecondition. Thus, there was a significant interactionof naltrexone and alcohol.

There also were interactions between naltrexoneand alcohol on the short and long recall tasks, withthe drug combination producing significantly greaterimpairment than the separate effects of the drugs.For no-delay numeric recall scores, there was an in-teraction of naltrexone 50 mg with moderate andhigh dose alcohol. For delayed numeric recall scores,

naltrexone 50 mg and naltrexone 100 mg in combina-tion with high dose alcohol produced significantdecrements in performance. In contrast to DSST per-formance, these interactions reflected greater decre-ments in performance following the combination ofactive alcohol and naltrexone rather than naltrex-one-induced improvement in performance in the ab-sence of active alcohol.

Blood Alcohol Levels

In the moderate alcohol dose condition, blood alco-hol level peaked 30 minutes following ingestion at a

mean of 0.048 mg/dL; blood alcohol level averagedacross the moderate alcohol dose sessions was 0.034mg/dL (S.E. .033). In the high alcohol dose condi-tion, blood alcohol level peaked 60 minutes follow-ing ingestion at a mean of 0.104 mg/dL; mean bloodalcohol level across the high alcohol dose sessionswas .088 mg/dL (S.E. .043). There were no differ-ences in mean or peak blood alcohol levels or time topeak BALs as a function of naltrexone dose condition(allp .10).

DISCUSSION

The present study findings provide strong support forthe involvement of the endogenous opioid system in al-cohol respones in that naltrexone administration altereda variety of subjective and objective measures of alcoholeffects. In the present study, naltrexone decreased sub-

jects ratings of desire to drink both prior to and follow-ing alcohol administration. In approximately half of thesubjects, this reduced urge for alcohol during naltrexonemaintenance was paralleled by changes in several objec-tive indicators of desire for alcohol including increased

drink refusal and slower rates of drinking. Further, self-reports of best Ive ever felt and like effects of cap-sule/drink were decreased across alcohol conditionsamong subjects receiving 50 mg compared to placebonaltrexone. Importantly, there was a significant interac-tion between alcohol and naltrexone such that naltrexone100 mg in combination with the high alcohol dose pro-duced greater decreases in ratings of best Ive ever feltand like effects of capsule/drink than those obtainedfor each drug separately. Naltrexone also increased seda-tive and sick/unpleasant effects following alcohol inges-tion. Subjective ratings of increased sick/unpleasant ef-fects were consistent with the increased nausea and

Table 3. Separate and Interactive Effects of Naltrexone and Alcohol on Psychomotor Performance. Arrows Indicate theDirection of Effect

PsychomotorEffects Nx 0 vs 50 Nx 0 vs 100 Nx 50 vs 100 Alc 0 vs Mod Alc 0 vs High Interactions

Balance-right b c

Balance-left c 50a

Circular lights b b a c c

DSST-attempted b c 100b, 100a

DSST-correct a c 100a

Short recall-correct b a 50b, 50b

Long recall-correct b a 50b, 100a

ap .05.bp .01.cp .001.Mmoderate alcohol doseH high alcohol dose50 naltrexone 50 mg100 naltrexone 100 mg


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vomiting observed following alcohol ingestion duringactive compared to placebo naltrexone sessions.

It is notable that subjects ratings of alcohol intox-ication (high and drunk) were not altered by naltrex-

one. This finding is in agreement with the compara-ble mean, peak and time to peak blood alcohollevels observed across naltrexone conditions, despitesome disruption of drinking behaviors by naltrexone.

Figure 3. Circular lights performance prior to and following the moderate (A) and high alcohol dose (B) as a function of nal-trexone dose condition. Symbols indicate means across subjects in each dose condition at each time point. Symbols to the left ofthe 0 time point represent baseline scores prior to alcohol administration. Naltrexone doses include placebo (), 50 mg (), and100 mg ( ). Scores represent the number of lights that subjects extinguished in a 60-second period.


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Also, the objective psychomotor measures generallyconfirmed the similar subjective ratings of intoxicationduring active and placebo naltrexone sessions. Naltrex-one produced systematic impairment only on circularlights performance. Results on the remaining psycho-motor tasks were inconsistent and the actual magnitude

of these effects was fairly small.The results of the present study support and extend

findings from earlier laboratory studies of naltrexoneseffects on alcohol responses. Our findings of decreasedliking and increased sedative effects associated with ac-tive naltrexone support the earlier observations bySwift et al. (1994), although no change in sedative ef-fects was observed in two recent studies (Davidson etal. 1996; King et al. 1997). For example, Doty and col-leagues (1997) failed to observe effects of naltrexone (25or 50 mg) on stimulant or sedative responses to alcoholingestion; however, their findings may be limited by

several study design considerations including use oflight-to-moderate social drinkers as study subjects,acute administration of the naltrexone dose one hour

before alcohol ingestion, and selection of a very low al-cohol dose (0.25) g/kg that produced only mild subjec-tive effects. Our findings of somewhat limited effects onpsychomotor responses agree with earlier reports of nosignificant effects of naltrexone compared to placebo onalcohol-related decrements in reaction time and mem-ory tasks (Swift et al. 1994). Of particular interest, therewas no indication of increased nausea at baselineamong subjects receiving active naltrexone. Addition-ally, our observation of increased self-reports of nausea

and unpleasant/sick effects as well as the increasedlikelihood of vomiting following active but not placeboalcohol refutes suggestions that decreased alcoholconsumption is a non-specific effect of naltrexone asso-ciated with general nausea or unpleasant subjective ef-fects in the absence of alcohol consumption. Thisobservation of naltrexone-precipitated nausea only inthe presence of active alcohol is in line with earlierreports (Davidson et al. 1996; King et al. 1997; Swift etal. 1994). Our observations of increased drink refusaland delay in drink completion extend the recent re-port of delays in initiating drinking among subjects

on 50 mg naltrexone (Davidson et al. 1996), althoughDavidson and colleagues did not find differences innumber of drinks requested or time to drink comple-tion. Finally, none of the laboratory studies conductedto date including the present report have observeddifferences in alcohol pharmacokinetic parameters in-cluding peak, time to peak and area under the curveas a function of naltrexone dose (King et al. 1997;Swift et al. 1994).

Results of the present study also are informativewith respect to observations in the earlier clinical trialswith alcohol-dependent patients. As was observed by

Volpicelli and colleagues (1992), subjects in the present

study who received 50 mg compared to placebo nal-trexone reported reduced desire to drink at baseline inthe absence of alcohol; a similar trend of decreasedcraving was observed for subjects on 100 mg naltrex-one. Importantly, the present study has extended thesefindings on craving to include the post-alcohol inges-

tion period. Our findings indicate that subjects receiv-ing 100 mg naltrexone also report decreased desire todrink following alcohol ingestion. Increased drink re-fusal and a slower pace to drink completion also wereobserved and could be interpreted as objective indica-tors of these self-reported changes in desire to drink.These findings are noteworthy since, across the pub-lished clinical trials, naltrexone appeared to differen-tially affect risk of return to heavy drinking but not riskof any drinking. That is, naltrexone- and placebo-treated subjects were equally likely to ingest an alcoholdrink, but naltrexone-treated subjects were significantly

less likely to continue drinking to alcohol relapse. Ourfindings of nausea only following active alcohol inges-tion suggest that some of the risk of increased nauseaassociated with naltrexone ingestion in the earlier clini-cal trials (Croop et al. 1997) may be related to subjectsdrinking status and not a medication side-effect alone.Finally, in the earlier clinical trial by Volpicelli and col-leagues, naltrexone-treated subjects who did drink re-ported less high than placebo-treated subjects whodrank, although no differences were observed in re-ported intoxication, craving, or loss of temper (Volpi-celli et al. 1995). In the present study, self-reported highfollowing alcohol ingestion was not decreased in either

naltrexone dose condition. This difference may stemfrom a greater range of descriptive terms available tocharacterize alcohol effects in the current study, allow-ing a greater refinement in subjects responses. Alterna-tively, as the authors suggest, it may indicate that ear-lier findings were a result of reduced alcoholconsumption by naltrexone versus placebo subjects(Volpicelli et al. 1995).

The present study has several design strengths. First,subjects were housed on an inpatient research unitthroughout each naltrexone dosing cycle. We were ableto observe naltrexone ingestion and can rule out medi-

cationnoncompliance as a factor in the study findings.Inpatient hospitalization also minimized the risk of un-authorized alcohol ingestion or drug use during the ac-tive dosing periods. Second, the study used a within-subject design, crossing all alcohol and naltrexonedoses for each subject. This design increased the statisti-cal power of our study to observe main and interactioneffects of naltrexone and alcohol, given that such hu-man laboratory studies often have relatively small sam-ple sizes. Finally, we selected a chronic dosing modelfor naltrexone administration. This procedure moreclosely parallels naltrexones use in clinical popula-tions, increases the likelihood that naltrexone and b-nal-


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trexol (the major metabolite of naltrexone) are atsteady-state across alcohol dose conditions, and de-creases the risk of acute, naltrexone-induced nausea in-terfering with the study measures.

Despite these design strengths, there also were twopotential limitations to the current study. First, the

study sample consisted of heavy drinkers rather thanalcohol-dependent subjects. At present, there is a lack ofconsensus on the most appropriate population for labo-ratory studies involving alcohol administration. Cur-rent Institutional Review Board and National Instituteon Alcohol Abuse and Alcoholism guidelines discour-age the conduct of alcohol challenge studies in alcohol-dependent persons. Further, conducting laboratorystudies in alcohol-dependent persons who may be un-dergoing alcohol withdrawal clearly creates another setof interpretative problems. Because of these concerns,the heavy drinking population seems to be a reasonable

surrogate for alcohol-dependent subjects. The fact thatour laboratory results parallel many of the clinical trialfindings for naltrexone in alcohol dependent subjectsprovides face validity to the subject selection used inthis study. Also, the growing clinical interest in prophy-lactic use of naltrexone for management of heavy drink-ing in non-alcohol dependent persons increases the di-rect clinical relevance of the current findings. Second,almost half of the subjects acknowledged marijuana useand one-quarter reported occasional cocaine use; it isnot known how this other drug use may influence nal-trexones effects on alcohol responses. Although sub-

jects were instructed to report for each inpatient admis-

sion alcohol and drug free, there was no fool-proofmethod to completely eliminate substance use. Severalprocedures were put into place to minimize the poten-tial impact of any substance use: subjects underwent a3-day inpatient stay before alcohol dosing procedures

began; urine screens and breathalyzer results were ob-tained at each inpatient admission and randomlythroughout patients 8-day inpatient stays. Two sub-

jects were excluded as a result of urinalysis evidence ofdrug use during the GCRC stay. Thus, we can be rea-sonably confident that current study findings reflect theinteraction of naltrexone and alcohol only and not the

interaction with other drugs.A primary purpose of this study was to examine the

interactions of naltrexone and alcohol dosage levels inan effort to address the practical issue of optimal nal-trexone dosing for clinical effectiveness. In examiningthe main effects of 50 mg and 100 mg naltrexone, therewas in general little evidence of a naltrexone dose-effectfunction. Specifically, both doses increased sedativeand unpleasant/sick effects following alcohol adminis-tration, and neither dose decreased self-reports of intox-ication. However, although naltrexone 50 mg was moreeffective in decreasing baseline reports of desire todrink, only the high naltrexone dose condition reduced

craving following alcohol administration. Perhaps mostimportantly, the high dose of naltrexone was especiallyeffective in decreasing reported well-being and liking ofeffects after subjects had consumed the high dose of al-cohol. These findings would seem to suggest that opti-mal naltrexone dosing may be best determined by a pa-

tients risk for heavy drinking during treatment.Our findings highlight the importance of including a

range of doses in research examining naltrexone effectson alcohol responses, since interactions can occur atdose combinations that would be missed if only a singledose of either drug were studied. Also, the presentstudy results highlight several key areas for further ex-amination in laboratory and clinical trials research. Spe-cifically, it will be important to examine closely the tim-ing and context of reports of naltrexone-precipitatednausea to sort out true medication side-effects from nal-trexone-alcohol interactions. Also, naltrexones effects

on craving both in the presence and absence of alcoholshould be followed up to better understand the rolethat these play in helping to prevent relapse in recentlyabstinent alcoholics. Finally, if desire to drink, best andliking are indeed opioid modulated effects of alcohol,the ability of naltrexone to attenuate these responsescontinues to support the premise that naltrexones ef-fects are mediated via blockade of opiate receptors. Fur-ther research is still needed to fully understand thesemechanisms of naltrexones actions.

ACKNOWLEDGMENTS

A portion of this work was presented at the 1997 meeting ofthe Research Society on Alcoholism. The study was supported

by USPHS grant R01-AA09569 and Johns Hopkins BayviewMedical Center General Clinical Research Center grant M01-RR02719. The authors thank Joseph Bezold, Shing Lee, and

John Yingling for their help in conducting this research andanalyzing the data.

REFERENCES

Altshuler HL, Phillips PE, Feinhandler DA (1980): Alterationof ethanol self-administration by naltrexone. Life Sci-ences 26:679688

Bigelow GE, and Walsh SL (1998): Evaluation of potentialpharmacotherapies: Response to cocaine challenge inthe human laboratory. In Higgins, ST, Katz, JL (eds),Cocaine Abuse: Behavior, Pharmacology, and ClinicalApplications. California, Academic Press, pp 209238

Boyle AEL, Stewart RB, Macenski MJ, Spiga R, Johnson BA,Meisch RA (1998): Effects of acute and chronic doses ofnaltrexone on ethanol self-administration in rhesusmonkeys. Alcohol Clin Exp Res 22:359366

Croop RS, Faulkner EB, Labriola DF, for The NaltrexoneUsage Study Group (1997): The safety profile of naltrex-


13/13


one in the treatment of alcoholism. Archives GeneralPsychiatry 54:11301135

Czirr SA, Hubbell CL, Reid LD (1987): Daily water depriva-tion potentiates ethanol intake beyond a period of waterintake. Alcohol 4:117120

Davidson D, Amit Z (1997): Effect of ethanol drinking and

naltrexone on subsequent drinking in rats. Alcohol14:581584

Davidson D, Swift R, Fitz E (1996): Naltrexone increases thelatency to drink alcohol in social drinkers. Alcohol ClinExp Res 20:732739

Doty P, de Wit H (1995): Effects of naltrexone pretreatmenton the subjective and performance effects of ethanol insocial drinkers. Behav. Pharmacol 6:386394

Doty P, Kirk JM, Cramblett MJ, de Wit H (1997): Behavioralresponses to ethanol in light and moderate social drink-ers following naltrexone pretreatment. Drug and Alco-hol Dependence 47:109116

Froehlich JC, Harts J, Lumeng L, Li TK (1990): Naloxoneattenuates voluntary ethanol intake in rats selectivelybred for high ethanol preference. Pharmacology, Bio-chemistry & Behavior 35:385390

Gianoulakis C (1990): Characterization of the effects of acuteethanol administration on the release of beta-endorphinpeptides by the rat hypothalamus. European Journal ofPharmacology 180:2129

Gianoulakis C, Krishnan B, Thavundayil J (1996): Enhancedsensitivity of pituitary beta-endorphin to ethanol in sub-jects at high risk of alcoholism. Archives of General Psy-chiatry 53:250257

Haertzen CA (1974): An overview of Addiction ResearchCenter Inventory scales (ARCI): An appendix and man-ual of scales. Vol. DHEW Publication No. (ADM) 7492.

National Institute on Drug Abuse, Rockville, MDHubbell CL, Czirr SA, Hunter GA, Beaman CM, LeCann NC,

Reid LD (1986): Consumption of ethanol solution ispotentiated by morphine and attenuated by naloxonepersistently across repeated daily administrations. Alco-hol 3:3954

Hubbell CL, Marglin SH, Spitalnic SJ, Abelson ML, Wild KD,Reid LD (1991): Opioidergic, serotonergic, and dopa-minergic manipulations and rats intake of a sweetenedalcoholic beverage. Alcohol 8:355367

Hyytia P, Sinclair JD (1993): Responding for oral ethanolafter naloxone treatment by alcohol-preferring AA rats.Alcohol Exp Clin Res 17:631636

King AC, Volpicelli JR, Frazer A, OBrien CP (1997): Effect ofnaltrexone on subjective alcohol response in subjects athigh and low risk for future alcohol dependence. Psy-chopharmacology 129:1522

Krishnan-Sarin S, Portoghese PS, Li TK, Froehlich JC (1995):The delta opioid receptor antagonist naltriben selec-tively attenuates alcohol intake in rats bred for alcoholpreference. Pharmacology, Biochemistry & Behavior52:153159

Li XW, Li TK, Froehlich JC (1996): Alcohol alters preproen-kephalin mRNA content in the shell and core of thenucleus accumbens. Alcoholism: Clinical and Experi-mental Research 20:53

McCaul ME, Turkkan JS, Svikis DS, Bigelow GE (1990): Alco-

hol and secobarbital effects as a function of familial alco-holism: Acute psychophysiological effects. Alcoholism:Clinical and Experimental Research 14:704712

McLeod DR, Griffiths RR, Bigelow GE, Yingling J (1982): Anautomated version of the digit symbol substitution task(DSST). Behavior Research, Methods & Instrumentation14:463466

Myers RD, Borg S, Mossberg R (1986): Antagonism by nal-trexone of voluntary alcohol selection in the chronicallydrinking macaque monkey. Alcohol 3:383388

OMalley SS, Jaffe AJ, Chang G, Schottenfeld RS, Meyer RE,Rounsaville B (1992): Naltrexone and coping skills ther-apy for alcohol dependence. A controlled study.Archives of General Psychiatry 49:881887

OMalley SS, Jaffe AJ, Rode S, Rounsaville BJ (1996): Experi-ence of a slip among alcoholics treated with naltrex-one or placebo. American Journal of Psychiatry 153:281283

Phillips TJ, Wenger CD, Dorow JD (1997): Naltrexone effectson ethanol drinking acquisition and on established etha-

nol consumption in C57BL/6J mice. Alcohol Clin ExpRes 21:691702

Reid LD, Delconte JD, Nichols ML, Bilsky EJ, Hubbell CL(1991): Tests of opioid deficiency hypotheses of alcohol-ism. Alcohol 8:247257

Reid LD, Gardell LR, Chattopadhyay S, Hubbell CL (1996):Periodic naltrexone and propensity to take alcoholicbeverage. Alcohol Clin Exp Res 20:13291334

Schuckit MA (1980): Self-rating of alcohol intoxication byyoung men with and without family histories of alco-holism. Journal of Studies on Alcohol 41:242249

Selzer ML (1971): The Michigan Alcoholism Screening Test:The quest for a new diagnostic instrument. American

Journal of Psychiatry 127:16531658

Spitzer RL, Williams JB W (1987): Structured Interview forDSM-IIIR (SCID). New York State Psychiatric Institute,Biometrics Research, New York

Swift RM, Whelihan W, Kuznetsov O (1994): Naltrexone-induced alterations in human ethanol intoxication.American Journal of Psychiatry 151:14631467

Volpicelli J, David MA, Olgin JE (1986): Naltrexone blocksthe post-shock increase of ethanol consumption. LifeSciences 38:841847

Volpicelli JR, Alterman AI, Hayashida M, OBrien CP (1992):Naltrexone in the treatment of alcohol dependence.Archives of General Psychiatry 49:876880

Volpicelli JR, Watson NT, King A, Sherman CE, OBrien CP(1995): Effect of naltrexone on alcohol high in alcohol-ics. Am J Psychiatry 152:613615

Wand GS, Mangold D, El Diery S, McCaul ME, Hoover D(1998): Offspring from families with a high density ofalcohol dependent individuals have altered endogenousbrain opioidergic activity. Archives of General Psychia-try 55:11141119

Weiss F, Mitchiner M, Bloom FE, Koob GF (1990): Free-choice responding for ethanol versus water in alcoholpreferring (P) and unselected Wistar rats is differen-tially modified by naloxone, bromocriptine, and methy-sergide. Psychopharmacology 101:178186

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