Lecture 5: Principles of Drug Administration Drug …nur.uobasrah.edu.iq/images/pdffolder/5....

Lecture 5:

Principles of Drug Administration

Drug Therapy in Special Populations

Objectives

Upon completion of this lecture, student will be able to

1. Describe the roles and responsibilities of nurses regarding

safe drug administration

2. Discuss the different routes of drug administration

3. Discuss the influences of the patient’s age on the effects of

drugs and drug responses

4. Discuss the pharmacological process and associated

changes in various patient age groups.

24-Nov-18

o Nurses are continually challenged to ensure that their

patients are given the correct medication at the correct time.

o Although many obstacles are encountered by nurses on

daily basis, nurses are both ethically and legally responsible

for correct administration of drugs.

o For safe and accurate drug administration (correct drugs

administration), the nurses

must have a physician’s order before administration of

medication

should use the “Six Rights” and three checks as a guideline

should minimize the use of abbreviations for drug names,

doses, routes of administration, and times of administration

because errors occurring with incorrect or misinterpreted

abbreviations. 24-Nov-18

Common abbreviations and their meanings

24-Nov-18

• Pharmaceutical Formulation: الصيدالنيةصياغة المستحضرات

• It is the method by which a drug is prepared – the process in which different chemical substances, including the active drug, are combined to produce a final medicine product.

• Dosage Form It is the form in which the above : شكل الجرعةformulation can be administered to a patient. e.g. as tablet, capsule, syrup or injection etc.

o Drug Formulation and dosage forms vary according to the:

• Drug’s chemical and physical characteristics, • Reason for use, and • Route of drug administration. • Some drugs are available in only one dosage form; others

are available in multiple dosage forms — choosing a form that is best received by the patient will lead to a better total outcome.

24-Nov-18

Most of drugs can be administered by a variety

of routes – Major routes of drug administration

include:

• Enteral,

• Parenteral, and

• Topical

24-Nov-18

Additional methods of administration

• Intra-lesional (into a lesion)

• Intra-thecal (instilling drugs directly into CSF) or intra-spinal

• Intra-cardiac (into the heart)

• Intra-pleural

• Intra-arterial (administration is not by direct arterial injection but by means of a catheter that has been placed in an artery)

• Intra-articular (into a joint)

• These methods are used by physicians & in some cases by advanced practice registered nurses for medication administration.

24-Nov-18

Factors that determine the choice of drug administration routes, include:

1) Physical and chemical properties of the drug (drug characteristics).

2) The dosage form in which the drug is available

3) Site of desired action, systemic or local effects

4) Rate and extent of absorption of the drug from different routes

5) Effect of digestive juices and first pass metabolism on the drug.

6) Rabidity with which the response is desired – onset of action (routine treatment or emergency).

7) Accuracy of dosage required (I.V. & inhalation can provide fine-tuning).

8) The patient’s age and condition – unconscious, vomiting, etc. (Patient related factors or patient characteristics)

24-Nov-18

Advantages Disadvantages

• Easy and Convenient

• Non-invasive, and often

painless

• Potentially reversible, and

hence safer than parenteral

routes – no risk of fluid

overload, infection, or

embolism

• Ideal for self-medication -

does not need assistance

• Inexpensive

• Variability: absorption can be highly

variable from one patient to another

→ difficult to control the conc. of a

drug at its sites of action, and

therefore makes it difficult to control

the onset, intensity, and duration of

responses.

• Inactivation of some drugs by

gastric acid and digestive enzymes

• Possible nausea and vomiting from

local irritation

• Patient must be conscious and

cooperative 24-Nov-18

.

• The enteral route – Oral drug administration (PO) includes drugs

given by mouth and swallowed – designed to pass through the

gastrointestinal tract. It is the oldest and most common route

Sublingual or buccal route

24-Nov-18

• For sublingual and buccal administration, the tablet or

pellet containing the drug is not swallowed but kept in

the mouth –sublingually(under the tongue) and

buccally (held between the gum and the cheek).

• Parenteral: introduction of drugs by any route other than the

oral-gastrointestinal route (enteral) or topical, usually refers

to administration of drugs by injection.

• This route takes the drug directly into the tissue fluid or

blood without having to cross the intestinal mucosa.

• The four routes that nurses commonly use to administer parenteral medications are:

Intramuscular (I.M)

Intravenous (I.V)

Intra-dermal (I.D)

Subcutaneous (S.C or SQ) 24-Nov-18

• Advantages of parenteral routes: • This route provide a rapid onset of action & ensure high blood

levels of the blood. (Drug action is faster – emergencies).

• Used for drugs with poor absorption from intestine (e.g. heparin) or unstable in the GI environment (e.g., insulin).

• Can be used for unstable of seriously ill patients, unconscious, uncooperative, vomiting patient.

• Not cause gastric irritation and vomiting.

• No chances of interference by food or digestive juices.

• Liver is bypassed

• Disadvantages of parenteral routes: • The preparation has to be sterilized.

• The technique is invasive and painful.

• It needs assistance of another person (though self-injection is possible – insulin).

• There is chance of local tissue injury. In general, parenteral route is more risky than oral (enteral) route

24-Nov-18

Topical drugs are those applied locally to the skin or the membranous

linings of the eye, ear, nose, respiratory tract, urinary tract, vagina, and

rectum. It is often more convenient as well as encouraging to the patient.

In the form of lotion, ointment, cream, powder, paints, drops, spray,

suppositories or pessaries, (including transdermal patches).

These applications include the following:

• Dermatologic preparations. Drugs applied to the skin, the topical

route most commonly used.

• Instillations and irrigations. Drugs applied into body cavities or

orifices. These routes may include the eyes, ears, nose, urinary

bladder, rectum, and vagina.

• Inhalations. Drugs applied to the respiratory tract by inhalers,

nebulizers, or positive-pressure breathing apparatuses.

24-Nov-18

Transdermal Delivery System (Transdermal

therapeutic system). • The use of transdermal patches (skin patch on which the

drug has been implanted) provides an effective means of

delivering certain medications.

• Drugs administered by this route are readily absorbed

from the skin and provide systemic effects. Drugs to be

administered by this route avoid the first-pass effect in the

liver and bypass digestive enzymes

• e.g., nitroglycerin for angina pectoris and scopolamine for

motion sickness, estrogen, fentanyl,…..

24-Nov-18

• This type of drug system are slowly absorbed from the skin

patches and maintains a relatively constant blood

concentration. Thus administration is less frequent than

when the drugs are given by another route.

• In addition, this drug system causes fewer adverse

reactions and reduces the possibility of toxicity

24-Nov-18

Inhalation Routes

This route is particularly effective and convenient for

patients with respiratory complaints (such as asthma or

chronic obstructive pulmonary disease), because the drug is

delivered directly to the site of action, thereby minimizing

systemic side effects. E.g., bronchodilators, such as

albuterol, and corticosteroids, such as fluticasone.

This route also can be used for systemic effect, e.g. general

anesthesia.

24-Nov-18

Drug Therapy in Special Populations

Drug therapy across the life span

Life Span Considerations of Medication

Administration, include:

1) Drug therapy during pregnancy and breast-feeding

2) Drug therapy for pediatric patients

3) Drug therapy for Geriatric patients

24-Nov-18 Dr. Utoor Talib

Drug Therapy during Pregnancy and Lactation • The clinical challenge is to provide effective treatment for

the mother while avoiding harm to the fetus or nursing

infant.

• Drug use during pregnancy is common – between one/half

and two/thirds of pregnant women take at least one medication, and the majority takes more.

• In pregnant patients, as in all other patients, the benefits of

treatment must balance the risks – risks apply to the fetus as

well as the mother.

• Unfortunately, the risks for most drugs used in pregnancy

have not been established. The clinician is obliged to

balance risks versus benefits, without knowing what the

risks really are.

• Drugs are most commonly used during pregnancy as

nutritional supplements (iron, vitamins, minerals) 24-Nov-18

Dr. Utoor Talib

• Physiologic Changes During Pregnancy

• Physiologic changes in the kidney, liver, and GI tract that can

alter drug pharmacokinetics. Because of these changes, a

compensatory change in dosage may be needed.

• For some drugs, distribution and hepatic metabolism and

excretion increases during pregnancy – change in cardiac output,

plasma volume, and regional blood flow

• Tone and motility of the bowel decrease in pregnancy, causing

intestinal transit time to increase. Because of prolonged transit,

there is more time for drugs to be absorbed.

• Placental drug transfer: Essentially all drugs can cross the

placenta, although some cross more readily than other –drugs

that are lipid soluble cross the placenta easily, whereas drugs that

are ionized, highly polar, or protein bound cross with difficulty.

• Gestational Age and Drug Therapy

• Factors affecting Teratogenesis: Sensitivity of fetus to drug is

dependent upon

Timing of exposure

Ability of drug to pass into the fetal circulation

Intensity of exposure – Dosing, frequency and duration

• When drug is given in relation to the developmental stage –timing of exposure:

Pre-implantation (conception week 2)

Embryonic period (week 3 week 8 post conception)

Fetal period (week 9 40 weeks post conception or until birth term)

**Exposure during pre-implantation, the teratogen acts in an all-or-none response, because exposure to a teratogen either causes death of the embryo or has no effect – if dose is high enough →the fetus will die, if dose is sub-lethal → the fetus will recover

• Drugs are less likely to cause congenital malformations during this period because the baby’s organ systems have not yet begun to form.

** During the embryonic period, there is rapid development of

internal structures. This is the period of maximum sensitivity

to teratogens.

• Teratogenic agents taken during this phase can lead to

structural malformation and spontaneous abortion. The

specific abnormality depends on which organ is forming at

the time of exposure.

• Exposure to teratogens during the 1st trimester results in

gross malformations

** During the fetal period, there is continued growth and

maturation of the baby’s organ systems.

Exposure to teratogens during the fetal period (2nd and 3rd

trimesters) is more likely to produce slowed growth or

impaired organ function, rather than gross structural

malformations.


• Pregnancy Drug Categories

In 1983, an effort to prevent teratogenicity effects, the Food and Drug Administration (FDA) established a system for classifying drugs according to potential harm to the fetus.

According to this system, drugs can be put into one of five categories: A, B, C, D, & X.

Drugs in Risk Category A are the least dangerous. In contrast, drugs in category X are the most dangerous; these drugs are known to cause human fetal harm.

Drugs in category B, C & D are progressively more dangerous than drugs in category A & less dangerous than drugs in category X.


Drug therapy during Lactation

Drugs taken by lactating women can be excreted in breast

milk. As a general rule drugs given to nursing mothers

reach infants in much smaller amounts than drugs given to

pregnant women. Most drugs can be detected in milk, but

concentrations are generally too low to be harmful.

Drugs that are lipid soluble enter breast milk readily,

whereas drugs that are ionized, highly polar, or protein

bound tend to be excluded.

Nonetheless, prudence is always in order. If possible, drugs

should be avoided during breast-feeding; however, patients

with chronic illnesses may require medication therapy for

their own health.


Drug Therapy in Pediatrics • Most drug use in pediatrics is empiric in nature because few studies

have been done in that population. Until recently, the FDA did not

require drug trials in children. As a result, for many drugs given to

young patients we lack good information on dosing, pharmacokinetics, and the therapeutic and adverse effects.

• Drug therapy in pediatric patient requires special consideration because of the child’s changing size, developmental level, and organ function.

• Pediatric patients respond differently to drugs than do adults

(middle-aged people). These differences allow pediatric patients to

be a greater risk for medication errors, and for prolonged and intense responses.

•

• Pediatrics = all patients under age 16 • Pre-mature infants (< 36 weeks gestation), Full-term infants (36 – 40

weeks gestational age), Neonates (birth –1 month), Infants (1 month – 1 year), and Children (1–12 years old), and Adolescents (12 –16 years old)


Pharmacokinetic factors specific to pediatrics include:

Decreased gastric acid production and slower gastric emptying time.

Drugs are usually given less often because they are metabolized

(involves first-pass metabolism) and excreted slowly, due to immature

liver and kidney function. Complete maturation of the liver and

kidney develops by 1 year.

Increased absorption of topical medications (greater body surface area

and thinner skin). This ↑the risk of toxicity from topical drugs.

Decreased serum protein-binding sites (until age 1). There may be an

increase in serum medication level of protein-binding medications.

Intramuscular administration: drug absorption following IM injection

in the neonate is erratic and slower than in adults. Delayed absorption

is due in part to low blood flow through muscle during the 1st days of

postnatal life.


Site selection for intramuscular injections depends on age and size. In

infants, use thigh muscles. In children older than 18 months of age,

use deltoid muscles; injections are considered less painful than in

thigh muscles. In children older than 3 years of age, use gluteal

muscles.

Blood-brain barrier: the BBB is not fully developed at birth making

infant much more susceptible to drugs. As a result, drugs and other

chemicals have relatively easy access to the CNS, making the infant

especially sensitive to drugs that affect CNS function. Accordingly, all

medicines employed for their CNS effects (e.g. morphine,

Phenobarbital) should be given in reduced dosage.

By the age of 1 year, most pharmacokinetic responses are similar to those in adults.

• Hence, drug sensitivity in children over the age of 1 is more like that

of adults than of the very young – except drug-metabolizing

capacity is markedly elevated until the age of 2 years, and then

gradually declines. A further sharp reduction takes place at puberty, when adult values are reached).

24-Nov-18

Dr. Utoor Talib

Drug Therapy in Geriatric patients (65+ years) • Drug therapy in the elderly represents a special therapeutic

challenge:

− older pts are more sensitive to drugs than younger adults

− exhibit more variability in response

− they experience more adverse drug reactions & drug-drug interactions.

Social, economic, physiologic, and age related health factors place elderly patients at high risk for medical problems.

The goal of drug therapy in the elderly may be “care” rather than “cure”, elderly suffer from chronic illnesses, the usual objective is to reduce or control symptoms & improve quality of life since cure is generally impossible.

To help ensure that drug therapy is safe and effective (as possible), individualization of treatment is essential – to achieve the desired intensity and duration of effect of the drug in each individual patient.


The age-related physiologic changes or aging process can affect all phases of pharmacokinetics, there is a gradual, progressive decline in organ function; this decline can alter the absorption, distribution, metabolism, and excretion of drugs.

o Increased gastric pH (alkaline)

o Decreased GI motility and gastric emptying time

o Decreased blood flow through cardiovascular system, liver, and kidneys

o Decreased hepatic enzyme function

o Decreased kidney function and glomerular filtration rate

o Decreased protein-binding sites

o Decreased body water, increased body fat, and decreased lean body mass

Pharmacokinetic changes may be minimal in patients who have remained physically fit, whereas they may be dramatic in patients who have aged less gracefully.


Nursing interventions for older adults: Decreasing the risk of adverse medication effects

Promoting compliance.

• Measures that can reduce the incidence of adverse drug reactions include: The majority of adverse drug reactions in the elderly are avoidable and dose related – not idiosyncratic.

o Taking detailed drug history, including over-the counter medications.

o Accounting for the pharmacokinetic and pharmacodynamic changes that occur with aging.

o Initiating therapy with low doses.

o Assess/monitor for therapeutic and adverse effects

o Monitoring clinical responses and plasma drug levels to provide a rational basis for dosage adjustment.

o Employing the simplest regimen possible.

o Monitoring for drug-drug and drug-food interactions & iatrogenic illness.

o Periodically reviewing the need for continued drug therapy, and discontinuing medications as appropriate.

o Encouraging the pt to dispose of old medications. 24-Nov-18

Dr. Utoor Talib

Dr. Utoor Talib 24-Nov-18

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