Pharmacology and Toxicology
Core concepts
Master receptor pharmacology (agonists, antagonists, partial agonists, inverse agonists), dose–response relationships (potency vs efficacy), and the major neurotransmitter systems. Know mechanisms and key adverse effects for autonomic drugs, cardiovascular agents, antimicrobials, CNS drugs, and analgesics. Understand toxicology principles: dose–response for toxicity, therapeutic index, antidotes (e.g., naloxone for opioids, N-acetylcysteine for acetaminophen, atropine/pralidoxime for organophosphate poisoning), and the difference between predictable (Type A) and idiosyncratic (Type B) adverse reactions. Know cytochrome P450 induction and inhibition as a source of interactions.
Question traps
A frequent error is confusing potency with efficacy - a drug can be highly potent but have low maximal effect. Another is assuming an antagonist has no effect when there is constitutive receptor activity; an inverse agonist reduces it while a neutral antagonist does not. Watch for "which is the antidote" items where the distractor is a symptomatic treatment rather than a specific antidote.
Worked rule of thumb
For interaction questions, remember inducers (rifampin, carbamazepine, phenytoin, St. John's wort) lower substrate levels, while inhibitors (ketoconazole, erythromycin, grapefruit components) raise them. If a question describes a patient on a narrow-therapeutic-index drug who develops toxicity after starting a new agent, suspect inhibition first.
Study approach
For each drug class, memorize mechanism, major use, hallmark adverse effect, and one antidote or interaction.