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What is pharmacology?

What Is Pharmacology? – Pharmacology is the branch of medical and pharmaceutical science that studies drugs and their effects on living organisms.

In simple Words pharmacology explains:

• What a drug does to the Body

• What the body does to a drug

In short: Pharmacology = study of drugs + their actions on the body

Main areas of pharmacology

Pharmacodynamics

1. Study of how drugs Work
2. Mechanism of action, effects, side effects

Pharmacokinetics

1. Study of drug movement in the body
2. Absorption, Distribution, Metabolism, Excretion (ADME)

What is pharmacodynamics?

Pharmacodynamics is the branch of pharmacology that studies what a drug does to the body.

In short: Pharmacodynamics = how the drug works in the body

In simple words

Pharmacodynamics explains how a drug works and what effects it produces in the body.

It includes the study of

• Mechanism of action – how the drug acts at molecular or cellular level
• Receptors – drug–receptor interaction
• Dose–response relationship – effect of different doses
• Therapeutic effects – desired effects
• Side effects & adverse effects
• Drug potency and efficacy

Key concepts

• Receptors: proteins where drugs bind to produce effects
• Agonist: activates a receptor
• Antagonist: blocks a receptor
• Potency: amount of drug needed to produce an effect
• Efficacy: maximum effect a drug can produce

Example

1. Aspirin

Action: Inhibits COX enzyme

Effect: Reduces pain, fever, inflammation

This mechanism is pharmacodynamics

2. Salbutamol

Action: Stimulates β₂-adrenergic receptors

Effect: Bronchodilation (relieves asthma)

Receptor stimulation = pharmacodynamics

3. Atropine

Action: Blocks muscarinic receptors

Effect: Increases heart rate, decreases secretions

Receptor blockade = pharmacodynamics

4. Insulin

Action: Increases glucose uptake by cells

Effect: Lowers blood sugar

Cellular effect = pharmacodynamics

5. Propranolol

Action: Blocks β-adrenergic receptors

Effect: Decreases heart rate and blood pressure

Antagonist action = pharmacodynamics

6. Diazepam

Action: Enhances GABA activity

Effect: Sedation, muscle relaxation

Neurotransmitter modulation = pharmacodynamics

7. Omeprazole

Action: Inhibits proton pump (H⁺/K⁺ ATPase)

Effect: Decreases gastric acid secretion

Enzyme inhibition = pharmacodynamics

8. Morphine

Action: Stimulates opioid receptors

Effect: Pain relief (analgesia)

Receptor activation = pharmacodynamics

9. Furosemide

Action: Inhibits Na⁺-K⁺-2Cl⁻ transporter in kidney

Effect: Increased urine output

Renal action = pharmacodynamics

10. Metformin

Action: Decreases hepatic glucose production

Effect: Lowers blood glucose in diabetes

Metabolic effect = pharmacodynamics

What is pharmacokinetics?

Pharmacokinetics is the branch of pharmacology that studies what the body does to a drug.

In short: Pharmacokinetics = ADME = movement of drug in the body

In simple words

Pharmacokinetics explains how a drug moves through the body after administration.

It includes 4 main processes (ADME)

1. Absorption – How the drug enters the bloodstream
2. Distribution – How the drug spreads to tissues and organs
3. Metabolism – How the drug is chemically changed (mainly in liver)
4. Excretion – How the drug is removed from the body (mainly by kidneys)

Key pharmacokinetic terms

• Bioavailability – Amount of drug reaching blood
• Half-life (t½) – Time taken for drug concentration to reduce by half
• Clearance – Rate of drug removal from body
• Volume of distribution (Vd) – Distribution of drug in body

Examples 

1. Paracetamol

Absorption: Rapidly absorbed from the intestine

Metabolism: Metabolized in the liver

Excretion: Excreted through urine

This ADME process is pharmacokinetics

2. Amoxicillin

Absorption: Well absorbed orally

Distribution: Reaches lungs, urine, tissues

Excretion: Eliminated mainly by kidneys

Drug movement = pharmacokinetics

3. Insulin

Absorption: Absorbed slowly from subcutaneous tissue

Distribution: Circulates in blood

Elimination: Broken down by liver and kidneys

Absorption rate = pharmacokinetics

4. Diazepam

Distribution: Highly lipid-soluble, enters brain quickly

Metabolism: Metabolized in liver

Half-life: Long half-life

Distribution & half-life = pharmacokinetics

5. Gentamicin

Absorption: Poor oral absorption (given IV/IM)

Distribution: Limited tissue penetration

Excretion: Excreted unchanged in urine

Route & elimination = pharmacokinetics

6. Digoxin

Distribution: Large volume of distribution

Elimination: Renal excretion

Half-life: Increased in kidney disease

Vd & clearance = pharmacokinetics

7. Morphine

First-pass metabolism: Extensive liver metabolism

Bioavailability: Low oral bioavailability

First-pass effect = pharmacokinetics

8. Warfarin

Protein binding: Highly bound to plasma proteins

Metabolism: Metabolized by liver enzymes

Protein binding & metabolism = pharmacokinetics

 

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