Toxicology and antidotes
Practice questions with explanations

C. Urinary alkalinisation with potassium replacement, and haemodialysis for severe cases

Alkalinising urine and blood promotes excretion and reduces central nervous system penetration, and hypokalaemia prevents effective alkalinisation so potassium must be replaced. Dialysis is indicated for very high concentrations, renal failure, pulmonary oedema or altered mental state, and salicylate is well suited to removal by dialysis.

A. Acetylcysteine, which replenishes glutathione and detoxifies NAPQI

Acetylcysteine supplies cysteine for glutathione synthesis, allowing the reactive metabolite NAPQI to be conjugated before it binds hepatocyte proteins. It is close to fully protective when started within 8 hours of ingestion and still worth giving late, including in established hepatic failure. Charcoal is useful in the first hours to reduce absorption but is not an antidote.

B. Vitamin K with prothrombin complex concentrate for major bleeding

Vitamin K restores the ability to synthesise functional clotting factors but takes hours, so major bleeding also needs the factors themselves. Protamine reverses unfractionated heparin and partially reverses low molecular weight heparin. Idarucizumab is the specific antibody fragment for dabigatran, and andexanet alfa reverses the factor Xa inhibitors.