Pharmacology END Semester 3CAT: Drug OmpathStudy

MBPL3800 – Basic Pharmacology School of Pharmacy, Department of Pharmacology and Clinical Pharmacy MBChB Programme Paper 1 Duration: 2 Hours Total Marks: 70 --- SECTION A – Multiple Choice Questions (30 Marks) Question 1. What impacts drug response by changing number of receptors? a) Down regulation b) Receptor affinity c) Signal transduction d) Cell membrane fluidity Answer: a) Down regulation Explanation: Down-regulation is a homeostatic response where prolonged exposure to an agonist causes cells to internalize or reduce the number of surface receptors, lowering sensitivity to the drug over time. This is why some drugs (e.g., beta-agonists, opioids) show reduced effect with chronic use — a concept called tolerance. --- Question 2. What type of medication is griseofulvin? a) Antiretroviral b) Antibacterial c) Antifungal d) Antiviral Answer: c) Antifungal Explanation: Griseofulvin is an oral antifungal that concentrates in keratin-producing cells. It disrupts fungal mitosis by interfering with microtubule function, making it effective specifically against dermatophyte infections (ringworm, tinea). --- Question 3. What term refers to the amount of drug at the site of action? a) Bioavailability b) Half-life c) Absorption d) Biopharmaceutics Answer: a) Bioavailability Explanation: Bioavailability is the fraction of an administered dose that reaches systemic circulation unchanged, which correlates with how much drug is available to act at the target site. IV drugs have 100% bioavailability by definition. --- Question 4. Rimantadine is used to treat or prevent: a) Influenza A b) Influenza B c) Measles d) Mumps Answer: a) Influenza A Explanation: Rimantadine blocks the M2 ion channel protein, which is unique to the Influenza A virus and required for viral uncoating. It has no activity against Influenza B because that strain lacks this M2 channel. --- Question 5. Diphenhydramine is classified as which type of drug? a) Antibiotic b) ACE inhibitor c) Antihistamine d) Antifungal Answer: c) Antihistamine Explanation: Diphenhydramine is a first-generation H1-receptor antagonist. Because it crosses the blood-brain barrier, it causes sedation in addition to blocking peripheral allergic symptoms like itching and rhinorrhea. --- Question 6. Dactinomycin is identified as which type of medication? a) Antifungal agent b) Alkylating agent c) Antimetabolite d) Antitumor antibiotic Answer: d) Antitumor antibiotic Explanation: Dactinomycin intercalates between DNA base pairs, blocking RNA polymerase and halting transcription. It belongs to a class of naturally-derived antibiotics repurposed for chemotherapy, distinct from alkylating agents or antimetabolites. --- Question 7. What impacts oral absorption but not injectable bioavailability? a) Ionization b) First-pass metabolism c) P-glycoprotein transporters d) Lipophilicity Answer: b) First-pass metabolism Explanation: Orally absorbed drugs travel through the hepatic portal vein to the liver before reaching systemic circulation, where they may be extensively metabolized before ever acting. IV, IM, and SC routes bypass the portal circulation entirely, avoiding this effect. --- Question 8. Fluconazole is used to treat which type of infections? a) Viral b) Protozoal c) Fungal d) Bacterial Answer: c) Fungal Explanation: Fluconazole is a triazole antifungal that inhibits fungal cytochrome P450 (14-alpha-demethylase), blocking ergosterol synthesis and weakening the fungal cell membrane. --- Question 9. Enzymatic metabolism that introduces reactive groups is called: a) First-pass effect b) Phase I metabolism c) Dealkylation d) Glucuronidation Answer: b) Phase I metabolism Explanation: Phase I reactions (oxidation, reduction, hydrolysis — largely via cytochrome P450 enzymes) introduce or expose polar functional groups (like -OH), which then serve as attachment points for Phase II conjugation reactions. --- Question 10. Which medication is an antifungal in the polyene class? a) Fluconazole b) Amphotericin B c) Itraconazole d) Terbinafine Answer: b) Amphotericin B Explanation: Amphotericin B binds directly to ergosterol in the fungal cell membrane, forming pores that cause leakage of intracellular contents. Its broad activity comes at the cost of significant nephrotoxicity. --- Question 11. What statement best describes pharmacodynamics? a) Drug transit in the body b) Biologic response to a drug c) Liver enzyme metabolism d) Route of administration Answer: b) Biologic response to a drug Explanation: Pharmacodynamics is often summarized as "what the drug does to the body" — covering receptor binding, mechanism of action, and the dose-response relationship, as opposed to pharmacokinetics ("what the body does to the drug"). --- Question 12. Mercaptopurine is used to treat: a) Autoimmune disorders b) Cancer c) Tuberculosis d) Bacterial infections Answer: b) Cancer Explanation: Mercaptopurine is a purine antimetabolite that gets incorporated into DNA/RNA synthesis pathways, disrupting nucleoti