Basic Pharmacology

What is a drug?- any chemical agent which

effects any biological process

What is pharmacology ?

- the study of how drugs effect biological systems

Introduction

A. Physical Nature of Drugs Solid drugs -> oral route

aspirin or atropine Liquid drugs -> oral route, IM, SC

nicotine or ethanol Gaseous drugs -> inhalation

nitrous oxide, halothane, amylnitrite

Many drugs are weak acids or basespH differences in the body may alter the degree of

ionization of drug

What is Pharmacology ?

Pharmacology

Pharmacokinetics Pharmacodynamics

What the body does to drug What the drug does to body

Pharmacotherapeutics Pharmacocognosy

The study of the use of drugs Identifying crude materials as drugs

Toxicology

PharmacokineticsWhat the body does to the drug

- Absorption- Distribution- Metabolism (Biotransformation)- Excretion Half-life (t1/2)

- the time required for the plasmaconcentration of a drug to be reduced by 50 %

PharmacodynamicsWhat the drug does to the body

- Drug receptors- Effects of drug- Responses to drugs- Toxicity and adverse effects of drugs

Sources of DrugsPharmacocognosy

Animals

Plants

Minerals

Synthetic

Microbes

Many of these old sources are still in use todayFoxglove plant

Meadow flower Colchicum autumnale

Beef or pork pancreas

Digitalis comes from the foxglove plant and is used in the treatment of CHF

Colchicine is the drug of choice for treatment of gout

Insulin is used today to treat diabetes and is derived from the pancreas of beef or pork or may be synthetically produced as well.

Drugs Derived from Plants

Ephedrine is present in the leaves of a bushy shrub (species name Ephedra), which, when burned were used by the ancient Chinese to treat respiratory ailments. Today, it is a bronchodilator.

Many estrogen hormone replacement therapy drugs are derived from yams.

The belladonna plant – source of atropine, which is still used to dilate the pupils.

DRUG CLASSIFICATION

- Based on the chemical structure  

- Based on the main effect (e.g. analgesics).

- Based on the therapeutic use (e.g. antipsychotic).

-Based on mechanism of action (e.g. serotonin agonist).

 

Drug Nomenclature

- Chemical name - *Generic name - Trade name

Chemical Name: 2-(4-isobutylphenyl)-propionic acid

Generic Name: ibuprofen

Trade Names: Advil, Aches-N-Pain, Brufen, Emodin, Haltran, Medipren, Midol 200, Motrin, Nuprin, Rufen, Trendar, Wal-Profen

*preclinical nomenclature = company abbrev-123456 (e.g. WAY-100635, MK-869)

Routes of Administration Critical to efficacy

Rapidity of onsetDuration of effectsMagnitude of effects

Systemic administrationDrug into circulatory system via ...

Enteral routes Parenteral routes

Drug effects throughout body ~

Routes of Drug Administration

Enteral within or by way of the GI tract

Oral (PO), rectal, sublingual

Parenteral Not within the alimentary canal

Inhalation, IM, SC, IP, topical

Central Into the brain or spinal cord Intrathecal, ICV

Routes of Drug Administrationcommon abbreviations…

PO = per os = oral

IV = intravenous = into the vein

IM = intramuscular = into the muscle

SC = subcutaneous = between the skin and muscle

IP = intraperitoneal = within the peritoneal cavity

icv = intracerebroventricular =directly into the ventricle of the brain

Oral Per Os (PO)

by mouthabsorption across

membrane in GImost commonmost variable1st pass metabolism

Cooperation required Can recall ~

Oral Sublingual

Absorption: mucous membrane salivary glands

e.g., nitroglycerin, buprenorphine

Chewingabsorbed across lining of

mouth ~

Injection Intravenous (iv)

directly into vein rapid onset of effects

Fastest ~ Intramuscular (im)

Location important Deltoid - rapid Thigh - moderate Buttocks - slowest Difference in blood supply & distance

Routes of Drug Administration and Absorption.

Injecting (Intravenous): Puts drugs directly

into a vein

Put drugs into muscles or under skin

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Intravenous (IV)Intravenous (IV) 15 15 –– 30 seconds30 seconds

Intramuscular (IM) Intramuscular (IM) 3 3 –– 5 minutes5 minutes

SubcutaneousSubcutaneous 3 3 –– 5 minutes5 minutes

Injection

Subcutaneous (sc)under skinslow, steady absorption

DisadvantagesVariable absorption limited volumeskin irritations ~

Injection

Intrathecal under sheath of nerve fibers,

spinal cord, or brain Mostly as local anesthesia

little importance for most psychoactive drugs ~

Inhalation

Smoking Lungs

gases or vaporsdensely lined with capillaries large surface area

Fast absorptionSimilar to iv ~

Routes of Drug Administration and Absorption.

Inhaling: Allows the vaporized

drug to enter the lungs, the heart and then the brain in about 7-10 seconds (Most rapid)

(Pictures) Marijuana inhaling tent used

by the Scythians, c. 500 B.C. Man in India smokes ganja

(marijuana) in a “chillum” pipe.

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Inhaling: 7 to 10 secondsInhaling: 7 to 10 seconds

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Other routes

Transdermal patchesabsorbed by skinslow continuous release

also liposomes: via injection

Suppositories - rectal or vaginalabsorption incomplete & unpredictable

Pellets - Norplant Microcatheter & pump ~

Routes of Drug Administration and Absorption

Contact or Transdermal Absorption

Absorption through the skin is the slowest method of drug use. It often takes 1–2 days for effects to begin and the absorption can continue for about 7 days. Nicotine, fentanyl, and heart medications can also be absorbed this way

Skin creams & ointments absorbed through skin

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Contact or Contact or Transdermal: Transdermal: 1 to 2 days1 to 2 days

Toxicity

Toxicity is the ability of a chemical to damage an organ system, to disrupt a biochemical process, or to disturb an enzyme system.

Drug Formulation

Dosage = the amount of drug to be administeredusually based on weightExample: mg/kg

Concentration = how the drug is formulatedExample: mg/ml

Injection Volume = a liquid measurement based on weight

Example: ml/kg

Factors Affecting Response to Drugs

Dosage

Route of Administration IV IH subling IM, SC IP PO topical

Rate of Absorption

Rate of Elimination

Physiochemical properties of the drug

age, sex, species, metabolism, etc…

Drug-Receptor Interactions

Agonists activates or enhances

cellular activity. triggers a series of

biochemical events alteration in function second messengers:

biochemicals that initiate these changes

Antagonists do not initiate a change

in cellular function. prevent the binding and

the action of agonists “blockers”

Drug-Receptor Interactions

Factors Governing Drug Action

1. Affinity: measure of the tightness that a drug binds to the receptor

2. Intrinsic activity: measure of the ability of a drug to generate an effect, producing a change in cellular activity

Binding of a drug

drug must interact with complementary surfaces on the receptor.

Antagonist

exhibit affinity for the receptor do not have intrinsic activity at the receptor competitive antagonist: binds to the receptor

in a reversible mass-action manner

-agonists given in high concentrations can displace the antagonist from the receptor

-agonist can then produce its effect