25/03/2025
# # # **Basic Pharmacology of Drugs**
Pharmacology is the study of how drugs interact with living systems, including their **mechanisms of action, effects, and side effects**. Here’s a simplified breakdown of key concepts:
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# # **1. What is a Drug?**
A **drug** is any chemical substance that affects the body’s functions, used for:
- **Treatment** (e.g., antibiotics for infection)
- **Prevention** (e.g., vaccines)
- **Diagnosis** (e.g., contrast dyes in imaging)
- **Altering physiological functions** (e.g., painkillers, stimulants)
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# # **2. Drug Classification**
Drugs can be classified based on:
# # # **A. Source**
- **Natural** (e.g., morphine from o***m, penicillin from fungus)
- **Synthetic** (e.g., aspirin, paracetamol)
- **Biotechnological** (e.g., insulin, monoclonal antibodies)
# # # **B. Mechanism of Action**
- **Receptor Agonists** (activate receptors, e.g., morphine for pain)
- **Receptor Antagonists** (block receptors, e.g., antihistamines for allergies)
- **Enzyme Inhibitors** (e.g., aspirin blocks COX enzymes)
- **Ion Channel Modulators** (e.g., calcium channel blockers for blood pressure)
# # # **C. Therapeutic Use**
- **Analgesics** (painkillers)
- **Antibiotics** (kill bacteria)
- **Antihypertensives** (lower blood pressure)
- **Antidepressants** (treat depression)
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# # **3. Pharmacokinetics (What the Body Does to the Drug)**
How the body **absorbs, distributes, metabolizes, and excretes** a drug:
1. **Absorption**
- How the drug enters the bloodstream (oral, IV, topical, etc.).
- Affected by food, pH, and drug formulation.
2. **Distribution**
- How the drug spreads to tissues (affected by blood flow, protein binding).
3. **Metabolism**
- Liver enzymes (e.g., **CYP450**) break down drugs.
- Some drugs become active only after metabolism (**prodrugs**).
4. **Excretion**
- Drugs are removed via **kidneys (urine), liver (bile), lungs, or sweat**.
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# # **4. Pharmacodynamics (What the Drug Does to the Body)**
How drugs produce their effects:
- **Dose-Response Relationship**
- Higher dose → stronger effect (up to a maximum).
- **Therapeutic Index (TI)**
- Ratio of **toxic dose** to **effective dose** (higher TI = safer drug).
- **Side Effects vs. Adverse Effects**
- **Side effect** = expected, mild (e.g., drowsiness from antihistamines).
- **Adverse effect** = harmful (e.g., liver damage from paracetamol overdose).
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# # **5. Common Drug Examples & Their Actions**
| **Drug Class** | **Example** | **Mechanism** | **Use** |
|----------------------|-------------------|----------------------------------------|-----------------------------|
| **NSAIDs** | Ibuprofen | Blocks COX enzymes → reduces inflammation | Pain, fever, inflammation |
| **Beta-Blockers** | Propranolol | Blocks β-adrenergic receptors → lowers heart rate | Hypertension, anxiety |
| **ACE Inhibitors** | Lisinopril | Blocks ACE → reduces blood pressure | Hypertension |
| **SSRIs** | Fluoxetine (Prozac) | Increases serotonin in the brain | Depression, anxiety |
| **Antibiotics** | Amoxicillin | Kills bacteria by disrupting cell wall | Bacterial infections |
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# # **6. Key Principles in Drug Use**
- **Placebo Effect**: Psychological benefit from inactive drugs.
- **Tolerance**: Reduced drug effect over time (e.g., opioids).
- **Dependence**: Physical/psychological need for a drug.
- **Drug Interactions**: Some drugs alter others’ effects (e.g., grapefruit juice affects CYP450 metabolism).
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# # # **Conclusion**
Understanding basic pharmacology helps in **safe and effective drug use**. Always:
✔ Follow prescribed doses.
✔ Check for interactions.
✔ Consult a doctor for persistent symptoms.
Would you like details on a specific drug class?
