Pharmacology & Therapeutics

Warfarin and the direct oral anticoagulants interrupt the clotting cascade at different points (vitamin K recycling versus a single activated factor), and that mechanistic difference dictates monitoring, dosing and how bleeding is reversed.

Digoxin's inhibition of the myocyte Na/K-ATPase pump raises intracellular calcium to boost contractility, but the same mechanism becomes arrhythmogenic in excess, and hypokalaemia potentiates toxicity because potassium and digoxin compete for the same binding site.

Lithium is handled by the kidney like sodium and has a narrow therapeutic index, so anything that promotes sodium and volume conservation drives lithium retention and pushes levels into a self-perpetuating, neurotoxic range.

Mu-opioid receptor agonism blunts the brainstem's response to rising carbon dioxide, causing the respiratory depression that actually kills, and naloxone reverses this by displacing the opioid, but often for less time than the opioid itself remains active.

A toxic metabolite overwhelms the liver's glutathione defences once conjugation pathways saturate, causing centrilobular hepatocyte necrosis that the antidote works by replenishing.

Excess stimulation of central and peripheral serotonin receptors from serotonergic drug combinations produces a rapid-onset triad of neuromuscular, autonomic and mental-state disturbance that resolves once the receptor drive is removed or blocked.