WEEK 1 pharmacokinetics and pharmacodynamics

Question 1

What is pharmacology?

Answer 1

Pharmacology is the study of drugs, which includes their origins, source,, actions, effects and uses.

The prefix ‘pharmaco-’ is derived from the Greek word pharmakon , meaning ‘drug’ or ‘medicine’.

Question 2

Define a drug

Answer 2

The World Health Organization defines the word ‘drug’ as ‘any substance or product that is used or intended to be used to modify or explore physiological systems or pathological states for the benefit of the recipient’.

Question 3

Define Pharmacokinetics

Answer 3

Pharmacokinetics is the branch of pharmacology that focuses on the study of how the body processes drugs. It involves the absorption, distribution, metabolism, and elimination (ADME) of drugs within the body.

Question 4

Define Absorption

Answer 4

Absorption refers to the process by which a drug enters the bloodstream from its site of administration (e.g., oral, intravenous, topical).

Factors affecting drug absorption include the drug’s formulation, route of administration, and the presence of food or other drugs.

Question 5

Define Distribution

Answer 5

Distribution: After absorption, drugs are distributed throughout the body’s tissues and organs.

Factors influencing drug distribution include blood flow, tissue binding, and the drug’s ability to cross cellular membranes (e.g., blood-brain barrier). Some drugs may accumulate in specific tissues or organs.

Question 6

Define Metabolism

Answer 6

Metabolism (Biotransformation): Metabolism is the chemical transformation of drugs into metabolites, often by enzymes in the liver.

Metabolism can make drugs more or less active, and it helps the body eliminate drugs more efficiently. The primary goal of drug metabolism is to convert drugs into water-soluble compounds that can be excreted.

Question 7

Define Elimination

Answer 7

Elimination (Excretion): Elimination is the removal of drugs and their metabolites from the body, typically through urine (renal excretion) or faeces (biliary excretion).

Kidneys and the liver play crucial roles in drug elimination. The rate of elimination affects a drug’s duration of action and potential for accumulation.

Question 8

What are the key concepts of pharmacokinetics?

Answer 8

Half life
Bioavailability
Drug interactions
First pass metabolism
Dosing regimen

Question 9

Define Half-life

Answer 9

The time it takes for half of the drug concentration in the bloodstream to be eliminated. It provides an estimate of how long a drug remains in the body.

Question 10

Define Bioavailability

Answer 10

The proportion of a drug that enters the bloodstream when administered via a specific route compared to intravenous (IV) administration. Bioavailability affects the effective dose of a drug.

Question 11

Define Drug interactions

Answer 11

Changes in pharmacokinetics or pharmacodynamics (the drug’s effects on the body) when two or more drugs are taken together. Interactions can lead to altered drug levels, efficacy, or safety.

Question 12

Define First pass metabolism

Answer 12

When orally administered drugs pass through the liver before entering the systemic circulation, they may undergo significant metabolism, potentially reducing their bioavailability.

Question 13

Define Dosing regimen

Answer 13

Determining the appropriate dose, frequency, and duration of drug administration based on pharmacokinetic parameters, therapeutic goals, and patient factors

Question 14

Define Pharmacodynamics

Answer 14

Pharmacodynamics is the branch of pharmacology that focuses on the study of how drugs exert their effects on the body, including the mechanisms of action, the relationship between drug concentration and response, and the effects of drugs on cellular and physiological processes.

Question 15

Define pharmacodynamic Mechanism of Action

Answer 15

This refers to how a drug interacts with specific molecules or receptors in the body to produce its effects. Drugs can act by binding to receptors, enzymes, ion channels, or other cellular components. For example, opioids like morphine act on opioid receptors in the brain to relieve pain.

Question 16

Define pharmacodynamic Dose-Response Relationship

Answer 16

Pharmacodynamics explores the relationship between the dose or concentration of a drug and its biological response. This relationship can be described by dose-response curves, which illustrate how drug effects change with increasing or decreasing doses.

Question 17

Define pharmacodynamic Potency and Efficacy

Answer 17

Potency refers to the amount of drug needed to produce a specific effect, while efficacy is the maximum effect that a drug can achieve. Potent drugs require lower doses to achieve their effects, while drugs with high efficacy produce a strong response.

Question 18

Define pharmacodynamic Agonists and Antagonists

Answer 18

Agonists are drugs that activate or enhance the activity of a receptor, while antagonists are drugs that block or inhibit receptor activity. For example, beta-agonists like salbutamol stimulate beta-adrenergic receptors to relax bronchial muscles, while beta-blockers like propranolol block these receptors to reduce heart rate and blood pressure

Question 19

Define pharmacodynamic Receptor Binding and Affinity

Answer 19

Drugs bind to receptors with varying degrees of affinity, which reflects how tightly a drug binds to its target. High-affinity drugs have a strong binding interaction with receptors.

Question 20

Define pharmacodynamic Therapeutic Index

Answer 20

The therapeutic index is the ratio between the minimum effective dose (the dose that produces a therapeutic effect) and the minimum toxic dose (the dose that causes harmful side effects). A higher therapeutic index indicates a safer drug.

Question 21

Define pharmacodynamic Desensitization and Tolerance

Answer 21

Over time, the body may become less responsive to a drug’s effects, leading to drug tolerance. This can result from receptor downregulation, decreased receptor sensitivity, or adaptive cellular changes. Desensitization and tolerance can impact drug efficacy.

Question 22

Define pharmacodynamic Duration of Action

Answer 22

Some drugs have a short duration of action, while others have a prolonged effect. The duration of action depends on factors like drug metabolism, elimination, and the binding affinity to receptors.

Question 23

Define pharmacodynamic Drug-Drug Interactions

Answer 23

Understanding how drugs interact with each other at the pharmacodynamic level is critical to prevent adverse effects or enhance therapeutic outcomes. Interactions can involve synergism (potentiating effects), antagonism (reducing effects), or alteration of drug metabolism