Three Phases of Drug Action Flashcards

Vocabulary-style flashcards covering the phases of drug action, absorption mechanisms, metabolic processes, and therapeutic/adverse effects.

Pharmaceutic Phase

The first phase of drug action consisting of disintegration and dissolution.

Disintegration

The breakdown of a tablet into smaller particles.

Dissolution

The process of dissolving smaller particles in the GI fluid before absorption.

Rate limiting

The time it takes for a drug to disintegrate and dissolve to become available for the body to absorb it.

Pharmacokinetic Phase

The second phase of drug action; the study of how the body processes drugs, involving what the body does to the drug.

Absorption

The movement of drug particles from the G.I. tract to body fluids.

Passive absorption

The movement of a drug from the site of administration into the bloodstream via diffusion (higher to lower concentration) without requiring energy.

Active absorption

A type of absorption that requires a carrier such as an enzyme or protein and requires energy to move across the membrane.

Pinocytosis

A process by which cells carry drugs across their membrane by engulfing the drug particles.

Bioavailability

The amount of drug available for action in the body after the first pass through the liver.

Enteric coating

A drug coating that allows it to dissolve only in an alkaline environment with a pH greater than $7.0$, such as the small intestine.

Sustained release drugs

Drugs designed to be released slowly over time rather than quickly like conventional tablets.

Distribution

The transport of drugs from the blood to the site of action.

Volume of Distribution ($V_d$)

The degree of distribution of a drug into various body compartments and tissue.

Metabolism (Biotransformation)

The process by which the body changes the chemical structure of a drug into another form called a metabolite, primarily occurring in the liver.

Metabolite

A more water-soluble compound formed during metabolism that can be easily excreted.

First Pass Phenomenon

The process where drugs absorbed through the small intestine undergo biotransformation in the liver before entering systemic circulation.

Pharmacogenetics

The study of hereditary influences on drug responses and variations in how individuals metabolize drugs.

Circadian Rhythms

The variations in drug absorption, hepatic clearance, half-life, and duration of action depending upon the time of day a drug is administered.

Excretion

The process where drugs are removed from the body, with the kidneys serving as the major organs.

Enterohepatic re-circulation

A process where drugs excreted in bile are reabsorbed when passing through the intestines from the liver.

Clearance of drugs

The elimination of drugs from circulation by all routes, affecting the drug's duration in the body and dosage requirements.

Plasma Half-life

The time it takes for the concentration of a drug in the plasma to be reduced by $50\%$.

Pharmacodynamic Phase

The third phase of drug action; the study of the mechanism of drug action on living tissue, or what the drug does to the body.

Curative effect

A therapeutic effect that cures a disease or condition.

Supportive effect

A therapeutic effect that supports a body function until other treatments or the body's response can take over.

Substitutive effect

A therapeutic effect that replaces body fluids or substances.

Chemotherapeutic effect

A drug action that destroys malignant cells or alters abnormal parasites/growths such as bacteria, viruses, or neoplastic tissue.

Restorative effect

A therapeutic effect that returns the body to health.

Adverse drug reaction (ADR)

An unwanted or harmful reaction experienced under normal conditions of use, usually requiring dose reduction or discontinuation.

Adverse event

Harm that occurs while a patient is taking a drug, regardless of whether the drug is suspected to be the cause.

Side-effect

Any effect caused by a drug other than the intended therapeutic effect, often less harmful and more predictable than an ADR.

Drug toxicity

Adverse effects that occur because the dose or plasma concentration has risen above the therapeutic range.

Drug abuse

The misuse of recreational or therapeutic drugs that may lead to addiction, physical/psychological harm, or death.

Hypersensitivity

An exaggerated adverse reaction to a drug, also known as an allergy.