Introduction to Pharmacology-History and Basic Terminology Used

This slide provides the information on the following topics:

1. Basic terminology used in pharmacology.
2. History of pharmacology.
3. Routes of administration with special reference to their advantages and disadvantages.

And by the end of this unit, you will be able to:

1. Define pharmacology and differentiate its major subfields
2. Understand and correctly use basic pharmacological terminology
3. Describe the historical evolution of pharmacology as a scientific discipline
4. Identify various drug administration routes and explain their advantages and disadvantages
5. Apply foundational knowledge to simple clinical scenarios

1. Pharmacology I  Nisha Adhikari Lecturer School of pharmacy B. Pharmacy

2. Reference Books: K.D. Tripathi’s "Essentials of Medical Pharmacology” Rang and Dale’s Pharmacology Goodman & Gilman’s The Pharmacological Basis of Therapeutics Katzung’s Basic and Clinical Pharmacology Lippincott’s Illustrated Reviews: Pharmacology © 2025 NISHA ADHIKARI

3. Unit I: Introduction to Pharmacology Topic: Basic terminology used in pharmacology. History of pharmacology. Routes of administration with special reference to their advantages and disadvantages. © 2025 NISHA ADHIKARI

4. 🎯 Learning Outcomes By the end of this unit, you will be able to: Define pharmacology and differentiate its major subfields Understand and correctly use basic pharmacological terminology Describe the historical evolution of pharmacology as a scientific discipline Identify various drug administration routes and explain their advantages and disadvantages Apply foundational knowledge to simple clinical scenarios © 2025 NISHA ADHIKARI

5. Topic: Basic terminology used in pharmacology © 2025 NISHA ADHIKARI

6. What is Pharmacology? 📚 Definition: Pharmakon ( φάρμακον ) = Drug / Medicine / Poison -logy ( λογία / logos) = Study / Discourse / Knowledge Pharmacology = The science or study of drugs and their effects on living organisms. © 2025 NISHA ADHIKARI

7. Pharmacology Pharmacology is the science of substances that interact with living systems through chemical processes , especially by binding to regulatory molecules and activating or inhibiting normal body processes. © 2025 NISHA ADHIKARI

8. Pharmacology Pharmacology is the branch of science that studies drugs in terms of: 🔬 Their origin 🧪 Chemical nature 🧬 Biological effects ⚙️ Mechanisms of action 💊 Therapeutic uses ⚠️ Side effects and toxicity © 2025 NISHA ADHIKARI

9. Pharmacology Pharmacology is the science of drugs (Greek: pharmakon—drug; logos—discourse), including their origin, composition, pharmacokinetics, therapeutic use, and toxicology.” It broadly deals with the interaction of chemical substances with living systems , with special emphasis on drug actions in humans . © 2025 NISHA ADHIKARI

10. Example: Paracetamol (Acetaminophen) Aspect Details Origin Synthetic compound developed in the late 19th century. Chemical Nature Aniline derivative; molecular formula: C₈H₉NO₂ Biological Effects Reduces fever (antipyretic) and pain (analgesic), no anti-inflammatory action Mechanism of Action Inhibits prostaglandin synthesis in the CNS and works on hypothalamic heat-regulating centers Therapeutic Uses Used for mild to moderate pain, fever, and as an alternative to NSAIDs Side Effects & Toxicity Safe in therapeutic doses, but overdose can cause liver toxicity due to accumulation of toxic metabolite (NAPQI) © 2025 NISHA ADHIKARI

11. introduction to Drug Names Chemical Name Generic Name Brand/Trade Name Example: Acetylsalicylic Acid → Aspirin → Ecosprin® N-acetyl-p-aminophenol (or 4-acetamidophenol) → Acetaminophen (U.S.) / Paracetamol (Europe/Asia/Nepal) → Cetamol®, Niko®, P-500® © 2025 NISHA ADHIKARI

12. SUBDIVISION of pharmacology Subdivisions: Pharmacodynamics Pharmacokinetics Pharmacotherapeutics Toxicology Clinical Pharmacology Chemotherapy © 2025 NISHA ADHIKARI

13. Branches of Pharmacology Branch Description Pharmacodynamics Study of drug effects and mechanisms Pharmacokinetics Study of drug movement in the body (ADME) Pharmacotherapeutics Clinical use of drugs Toxicology Study of harmful drug effects Clinical Pharmacology Drug use in humans, including trials Chemotherapy Use of drugs to destroy pathogens/tumors © 2025 NISHA ADHIKARI

14. Key Terminology - Part 1 Drug : Any substance that produces a biological effect Dosage: The specific amount of medication to be taken Receptor : Specific protein a drug binds to initiate effect Agonist/Antagonist : Activator/Blocker of receptors © 2025 NISHA ADHIKARI

15. Key Terminology - Part 1 Affinity and Efficacy : Binding ability and response strength Side Effect: An unintended effect of a drug Adverse Effect: A harmful or undesired effect Toxicity: The degree to which a substance can harm humans or animals Contraindication: A condition in which a drug should not be used © 2025 NISHA ADHIKARI

16. Key Terminology - Part 2 Potency vs. Efficacy Half-life (T1/2) Bioavailability Therapeutic Index First-Pass Metabolism Idiosyncrasy and Hypersensitivity © 2025 NISHA ADHIKARI

17. Potency vs. Efficacy Potency : The amount of drug needed to produce a given effect. A more potent drug produces the same effect at a lower dose . Example: Drug A (10 mg) produces the same effect as Drug B (100 mg) → Drug A is more potent. © 2025 NISHA ADHIKARI

18. Potency vs. Efficacy Efficacy : The maximum effect a drug can produce, regardless of dose. A drug with higher efficacy is more therapeutically useful . Example: Morphine has higher efficacy for pain relief than aspirin. 📌 Key Point : Potency = "How much?" | Efficacy = "How well?" © 2025 NISHA ADHIKARI

19. 2. ⏳ Half-life (T½) The time required for the concentration of the drug in the plasma to reduce by half . It determines how long a drug acts and how frequently it should be given. A drug with a long half-life needs less frequent dosing . A drug typically requires about 5 to 6 half-lives for more than 95% of it to be eliminated from the body. 🧠 Example: "If a drug has a half-life of 6 hours, it will take 6 hours for its plasma concentration to decrease from 100 mg to 50 mg." © 2025 NISHA ADHIKARI

20. 📊 Drug Remaining Over Time (Paracetamol-500 mg, t ₁/₂ = 6 hr) Time Amount Remaining (mg) % Remaining 0 hr 500 mg 100% 6 hr (1 half-life) 250 mg 50% 12 hr (2 half-lives) 125 mg 25% 18 hr (3 half-lives) 62.5 mg 12.5% 24 hr (4 half-lives) 31.25 mg 6.25% 30 hr (5 half-lives) 15.6 mg ~3.1% 36 hr (6 half-lives) 7.8 mg ~1.56% © 2025 NISHA ADHIKARI

21. 3. Bioavailability Bioavailability word breakdown: Bio = Life Availability = How much is accessible So, bioavailability refers to how much of a drug becomes available to the body’s systemic circulation in an unchanged (active) form after administration . It indicates the rate and extent to which the active drug ingredient is absorbed and reaches the bloodstream to produce its effect. © 2025 NISHA ADHIKARI

22. IV drugs = 100% bioavailability , because they go directly into the bloodstream. Oral drugs may have reduced bioavailability due to poor absorption or first-pass metabolism. © 2025 NISHA ADHIKARI 3. Bioavailability

23. 📌 Key Factors Affecting Bioavailability : Drug solubility Gastric pH First-pass metabolism Presence of food © 2025 NISHA ADHIKARI 3. Bioavailability

24. 4. Therapeutic Index (TI) A measure of drug safety . Defined as: TI= TD 50 ​​/ ED 50 where TD₅₀ = dose causing toxicity in 50% of population, and ED₅₀ = dose effective in 50% of population. A high TI = safer drug A low TI = narrow safety margin (e.g., digoxin, warfarin) © 2025 NISHA ADHIKARI

25. 5. First-Pass Metabolism The initial breakdown of orally administered drugs by the liver (and gut wall) before they reach systemic circulation. Reduces the bioavailability of certain drugs. 🧠 Example : Propranolol and nitroglycerin undergo significant first-pass metabolism → not effective orally in high doses. © 2025 NISHA ADHIKARI

26. 6. Idiosyncrasy and Hypersensitivity Idiosyncrasy : An unusual, unpredictable reaction to a drug, due to genetic variation . Not dose-related Example: Severe nausea and vomiting after a small dose of codeine in some individuals, even though most people tolerate it well. © 2025 NISHA ADHIKARI

27. 6. Idiosyncrasy and Hypersensitivity Hypersensitivity : An immune-mediated allergic reaction to a drug. Can be mild (rash) to severe (anaphylaxis) Example: Penicillin allergy © 2025 NISHA ADHIKARI

28. 📌 Key Difference : Idiosyncrasy = Genetic, non-immune Hypersensitivity = Immune reaction © 2025 NISHA ADHIKARI 6. Idiosyncrasy and Hypersensitivity

29. Topic: History of Pharmacology (Timeline) © 2025 NISHA ADHIKARI

30. Ancient Times ~3000 BC (Mesopotamia & Egypt) : Use of plant-based remedies (e.g., opium, castor oil, garlic) recorded in ancient texts like the Ebers Papyrus . Ayurveda (Indian subcontinent) and Traditional Chinese Medicine also began using herbal preparations. © 2025 NISHA ADHIKARI History of Pharmacology (Timeline)

31. 460–370 BC – Hippocrates (Greece) "Father of Medicine” Introduced the idea of disease having natural, not supernatural, causes. Emphasized rational drug use: “Let food be thy medicine...” © 2025 NISHA ADHIKARI History of Pharmacology (Timeline)

32. 3. 130–200 AD – Galen (Rome) Developed principles of compounding medications → " Galenicals ” Foundation for pharmacy and drug formulation. © 2025 NISHA ADHIKARI History of Pharmacology (Timeline)

33. Middle Ages to Renaissance ~1100–1600 AD Preservation and translation of medical texts by Arab scholars (e.g., Avicenna ). Growth of apothecaries in Europe. © 2025 NISHA ADHIKARI

34. 17 th –18 th Century – Rise of Scientific Method Focus shifted to experimental observation and chemical properties of substances. Discovery of compounds like morphine (1806, from opium) by Friedrich Sertürner . © 2025 NISHA ADHIKARI

35. 19 th Century – Birth of Modern Pharmacology Rudolf Buchheim (1847) : Founded the first pharmacology lab in Germany. Oswald Schmiedeberg (late 1800s) : "Father of Modern Pharmacology” Linked drug action to physiological responses . © 2025 NISHA ADHIKARI

36. 20 th Century – Rapid Expansion Discovery of penicillin (1928) by Alexander Fleming → antibiotics revolution. Development of chemotherapy , anesthetics , hormones , vaccines , psychotropic drugs . Pharmacology became a distinct scientific discipline . © 2025 NISHA ADHIKARI

37. 21 st Century – Molecular & Targeted Therapy Era Advances in genomics , biotechnology , monoclonal antibodies , gene therapy , and personalized medicine . Use of AI and computational pharmacology in drug design. © 2025 NISHA ADHIKARI

38. 📊 Summary of the History of Pharmacology Era Key Features / Milestones Ancient Era Use of herbs & natural remedies in Egypt, India, China. Texts like Ebers Papyrus, Ayurveda. Classical Period Hippocrates : Rational approach to disease. Galen : Drug compounding (Galenicals). 17 th –18 th Century Emergence of scientific method . Isolation of compounds like morphine . 19 th Century Buchheim founded first pharmacology lab. Schmiedeberg formalized modern pharmacology. 20 th Century Antibiotics (penicillin), anesthetics, vaccines. Development of clinical pharmacology . 21 st Century Molecular pharmacology , targeted therapies , biologics , and personalized medicine . © 2025 NISHA ADHIKARI

39. Evolution of Drug Development Natural to synthetic Empirical to rational design Animal studies to human clinical trials Regulatory evolution (FDA, ICH-GCP) © 2025 NISHA ADHIKARI

40. Topic: Routes of Drug Administration © 2025 NISHA ADHIKARI

41. Classification of Routes Enteral (Oral, Sublingual, Buccal, Rectal) Parenteral (IV, IM, SC, ID) Others : Topical, Transdermal, Inhalation, Nasal, Otic, Ophthalmic (Reference: Katzung, Chapter 3) © 2025 NISHA ADHIKARI

42. 1. Enteral Routes These routes involve the gastrointestinal (GI) tract . a. Oral (by mouth) route : Most common route Drug is swallowed and absorbed in the stomach or intestine Advantages: Convenient, Safe, Economical Disadvantages: Slow onset, affected by food, can be destroyed by stomach acid, and undergo first-pass metabolism (liver reduces drug effect before it reaches the bloodstream) © 2025 NISHA ADHIKARI

43. © 2025 NISHA ADHIKARI Oral Route

44. b. Sublingual (under the tongue) route: Drug is placed under the tongue and absorbed directly into blood vessels Advantages: Fast effect, bypasses the liver (no first-pass metabolism) Disadvantages: Only works for small, lipophilic (fat-soluble) drugs © 2025 NISHA ADHIKARI 1. Enteral Routes

45. c. Buccal route (between gums and cheek) : Drug is placed between the gum and inner cheek and absorbed directly into blood vessels in the oral mucosa. Advantages: Rapid absorption and onset of action Bypasses the liver, avoiding first-pass metabolism Useful when swallowing is difficult or drug is unstable in the GI tract Disadvantages: Limited to small doses Suitable mainly for lipophilic (fat-soluble) drugs Drug may be accidentally swallowed, reducing effectiveness © 2025 NISHA ADHIKARI 1. Enteral Routes

46. d. Rectal (through the rectum) route: Drug is inserted as a suppository or enema and absorbed by rectal mucosa Advantages: Useful if patient is vomiting or unconscious Disadvantages: Incomplete absorption, may be uncomfortable © 2025 NISHA ADHIKARI 1. Enteral Routes

47. 2. Parenteral Routes

48. 2. Parenteral Routes These routes bypass the GI tract and usually involve injections . Intravenous (IV): Drug is injected directly into a vein Advantages: Immediate effect, 100% bioavailability Disadvantages: Requires skilled personnel, infection risk © 2025 NISHA ADHIKARI

49. b. Intramuscular (IM): Drug is injected into a muscle (e.g., arm, thigh, buttock) Advantages: Suitable for oily or depot (long-acting) drugs Disadvantages: Can be painful; slower than IV © 2025 NISHA ADHIKARI 2. Parenteral Routes

50. c. Subcutaneous (SC): Drug is injected just under the skin Advantages: Slow and sustained absorption (e.g., insulin) Disadvantages: Not for large volumes © 2025 NISHA ADHIKARI 2. Parenteral Routes

51. d. Intradermal (ID): Drug is injected into the upper layer of the skin Used for: Allergy tests, BCG vaccine Disadvantages: Only a small volume can be used © 2025 NISHA ADHIKARI 2. Parenteral Routes

52. 3. Other Routes Topical: Applied to the skin or mucous membranes (e.g., cream, ointment) Used for: Local effects (e.g., rashes, fungal infections) © 2025 NISHA ADHIKARI

53. 3. Other Routes b. Transdermal: Drug is delivered across the skin using a patch Advantages: Slow, steady absorption into bloodstream (e.g., nicotine patch) © 2025 NISHA ADHIKARI

54. 3. Other Routes c. Inhalation: Drug is breathed into the lungs (e.g., asthma inhalers) Advantages: Fast effect, large surface area in lungs © 2025 NISHA ADHIKARI

55. 3. Other Routes d. Nasal: Drug sprayed into the nose Used for: Allergies, vaccines, hormones (e.g., nasal insulin) © 2025 NISHA ADHIKARI

56. 3. Other Routes e. Otic: Drops are placed in the ear Used for: Ear infections or wax removal © 2025 NISHA ADHIKARI

57. 3. Other Routes f. Ophthalmic: Drops or ointments used for eyes Used for: Eye infections, glaucoma © 2025 NISHA ADHIKARI

58. Summary Table Route Location Example Uses Notes Oral Mouth → GI tract Tablets, syrups Common, slow onset Sublingual Under tongue Nitroglycerin Rapid, no liver metabolism Buccal Between gum and cheek Tablets, films, lozenges Rapid onset, bypasses first-pass metabolism Rectal Rectum Suppositories Useful when vomiting IV Vein Emergency drugs Fastest, full dose IM Muscle Vaccines, antibiotics Moderate speed SC Under skin Insulin Slow, steady release ID Skin surface TB test, allergy test Very small amounts Topical Skin surface Creams, ointments Local effect only Transdermal Skin patch Nicotine, hormones Slow & long-lasting Inhalation Lungs Asthma inhaler Fast for respiratory issues Nasal Nose Nasal sprays Fast, some systemic effects Otic Ear canal Ear drops Local action Ophthalmic Eyes Eye drops Local action