Unit 1: Pharmacology and Drug Classes

• Topic 01

  Drug Classification Systems — Therapeutic Class vs Pharmacological Class

  45 questions
• Topic 02

  Cardiovascular Drugs — Antihypertensives, Statins, Anticoagulants, and Antiplatelets

  45 questions
• Topic 03

  CNS Drugs — Analgesics, Antidepressants, Anxiolytics, and Antipsychotics

  45 questions
• Topic 04

  Anti-infective Agents — Antibiotics, Antivirals, Antifungals, and Antiparasitics

  45 questions
• Topic 05

  Endocrine Drugs — Insulins, Thyroid Agents, and Corticosteroids

  45 questions
• Topic 06

  Respiratory Drugs — Bronchodilators, Inhaled Corticosteroids, and Antihistamines

  45 questions
• Topic 07

  GI Drugs — Antacids, PPIs, Antiemetics, and Laxatives

  45 questions
• Topic 08

  Top 200 Drugs — Brand/Generic Names, Drug Class, and Common Indications

  45 questions
• Topic 09

  Drug Interactions — Pharmacokinetic and Pharmacodynamic

  45 questions

A few questions from this unit, with the answer and a full explanation. The complete bank is available when you start practising.

1. Carvedilol (Coreg) is used for heart failure — which pharmacological class describes its mechanism of action most completely?

   • A
     Selective beta-1 adrenergic blocker without alpha-blocking activity
   • B
     ACE inhibitor with additional beta-blocking properties
   • C
     Non-selective beta-adrenergic blocker (beta-1 and beta-2) with additional alpha-1 adrenergic blocking activity
     Correct answer
   • D
     Potassium-sparing diuretic with beta-blocking activity
   Explanation

   Carvedilol (Coreg) is a non-selective beta-blocker (blocks beta-1 and beta-2 adrenergic receptors) that also blocks alpha-1 receptors. The alpha-1 blockade provides additional vasodilation, which is clinically beneficial in heart failure. Carvedilol is FDA-approved for HFrEF, hypertension, and post-MI left ventricular dysfunction. Key takeaway: carvedilol = non-selective beta-blocker + alpha-1 blocker; approved for HFrEF.

2. Which classification system groups drugs according to both the organ system acted on and their mechanism of action?

   • A
     The National Drug Code (NDC) system
   • B
     The WHO Anatomical Therapeutic Chemical (ATC) classification system
     Correct answer
   • C
     The DEA controlled substance schedule system
   • D
     The USP drug monograph classification system
   Explanation

   The WHO Anatomical Therapeutic Chemical (ATC) classification system organises drugs in a five-level hierarchy. The first level uses a letter to designate the anatomical main group (e.g., C = cardiovascular system). Lower levels progressively specify therapeutic, pharmacological, and chemical subgroups. For example, C09AA identifies ACE inhibitors (plain). This dual organisation — by organ system AND mechanism — distinguishes ATC from other classification systems. Key takeaway: the WHO ATC system classifies drugs hierarchically by organ system and mechanism of action.

3. N-acetylcysteine (NAC) is administered to a patient with acetaminophen overdose 10 hours after ingestion. The Rumack-Matthew nomogram places them in the 'possible risk' zone. What is the mechanism by which NAC reduces hepatotoxicity at this stage, even though peak NAPQI production has likely already occurred?

   • A
     NAC serves as a glutathione precursor and substitute, conjugating remaining NAPQI and supporting ongoing hepatic detoxification; it also has antioxidant and anti-inflammatory cytoprotective effects
     Correct answer
   • B
     NAC inhibits CYP2E1, halting further NAPQI production even at late time points
   • C
     NAC converts NAPQI back into acetaminophen via enzymatic reduction, reversing hepatic toxicity at any time point
   • D
     NAC directly binds NAPQI in the bloodstream before it reaches the liver, preventing any further hepatic injury
   Explanation

   N-acetylcysteine works through several complementary mechanisms: (1) it is rapidly converted to cysteine, a glutathione precursor, replenishing depleted hepatic glutathione that conjugates and detoxifies NAPQI; (2) it can directly conjugate NAPQI as an alternative substrate; (3) it has antioxidant properties that reduce oxidative stress in hepatocytes; (4) it improves hepatic microcirculation and oxygen delivery. Even when given late (8–24 hours), NAC is beneficial because detoxification is ongoing and residual NAPQI continues to cause injury. Key takeaway: NAC restores glutathione and provides direct detoxification of NAPQI; it is beneficial even when given 8–24 hours after acetaminophen ingestion.