Cardiovascular Drug Toxicity

Digoxin Toxicity: The Poisoned Pump and Its Antibody

Digoxin is one of the oldest drugs still in daily use — distilled from the foxglove, refined for two centuries, and yet still dangerous enough to poison a patient at a dose barely above the one that helps them. It has a narrow therapeutic window, a knack for accumulating quietly when the kidneys fail, and a toxidrome that runs from yellow-tinged vision to lethal arrhythmia. What redeems it is one of medicine's most elegant antidotes: an antibody fragment that binds the drug and physically peels it off the pump it poisoned. This is a story about a molecule that both strengthens and stops the heart — and about learning to tell which one is happening.

Beta-Blocker and Calcium-Channel-Blocker Overdose: Glucagon, Insulin and Beyond

Two of the most common cardiac prescriptions sit in almost every medicine cabinet — and taken in overdose they kill the same way: a heart too slow and too weak to keep blood moving. Beta-blockers and calcium-channel blockers arrive by different doors but end up in the same room, choking off the signal that tells the myocardium to beat harder. What makes them a rite of passage in toxicology is not the poisoning but the antidote — a strange, escalating toolkit where you reach past adrenaline for glucagon, then flood a failing heart with insulin, and, when all else fails, take over the circulation with a machine. This is where knowing the mechanism, not the monograph, saves the patient.

Local Anaesthetic Systemic Toxicity (LAST): The Lipid Rescue

Most poisonings arrive from the outside — a swallowed overdose, a bite, a bad batch. This one is different. Local anaesthetic systemic toxicity is a poisoning the clinician injects, in the operating theatre or the emergency department, in a fully awake patient, seconds before it happens. A nerve block that was meant to spare pain instead floods the bloodstream with a sodium-channel blocker, and the two most electrically excitable organs in the body — the brain and the heart — begin to fail in sequence. The reason every prescriber who wields a syringe of lidocaine must know it: the antidote is not a drug you reach for in cardiology. It is a bag of fat.