12th March 2024

Tricyclic antidepressant poisoning

Of the tricyclics, the drugs with the highest risk of toxicity are dothiepin and amitriptyline. The mechanism involves inhibition of the reuptake of norepinephrine and serotonin. In an overdose, the symptoms include anticholinergic effects (dry mouth, dilated pupils, urinary retention), cardiovascular effects (widened QRS, prolonged QT, sinus tachycardia) and CNS effects (drowsiness, convulsions, delirium). Acidosis, hypokalaemia and hypotension can be present in severe poisoning. Treatment includes IV sodium bicarbonate to alkalise the urine. Antiarrhythmic drugs should be avoided in most cases, as arrhythmias largely resolve with sodium bicarbonate and supportive care.