Pharmacology and Clinical Toxicology
Core concepts
Expect questions on pharmacokinetics (absorption, distribution, metabolism, excretion), pharmacodynamics (receptors, agonists/antagonists), and major drug classes with their mechanisms and adverse effects. Know high-yield toxicology: acetaminophen (NAC), salicylates (alkalinization), organophosphates (atropine plus pralidoxime), benzodiazepines (flumazenil caution), opioids (naloxone), and carbon monoxide (oxygen). Understand antidote-toxin pairings, the cytochrome P450 system and interactions, and therapeutic drug monitoring for narrow-index drugs (digoxin, lithium, warfarin, aminoglycosides).
Common traps
Toxicology questions often ask for the antidote or the first step. First step is usually ABC and decontamination considerations - not the antidote. Flumazenil can precipitate seizures in benzodiazepine-dependent patients and is generally avoided. Salicylate toxicity causes mixed respiratory alkalosis and metabolic acidosis; do not be fooled by a normal or high pH. Acetaminophen toxicity is treated based on the Rumack-Matthew nomogram timing, not just the level alone. Watch for enzyme inducers (rifampin, carbamazepine) vs inhibitors (erythromycin, ketoconazole).
Worked example
A patient presents 6 hours after ingesting acetaminophen. Rule of thumb: plot the serum level against time since ingestion on the nomogram; if above the treatment line, give N-acetylcysteine regardless of symptoms.
Rule of thumb
For any poisoning: stabilize first, identify the toxidrome, then give the specific antidote if indicated.