Tricyclic antidepressants + Cannabis - Drug Interactions

Clinical evidence,mechanism, importance and management

A 21-year-old woman taking nortriptyline 30mg daily experienced marked tachycardia (an increase from 90 to 160 bpm) after smoking a cannabis cigarette. It was controlled with propranolol (See reference number 1). A 26-year-old complained of restlessness,dizziness and tachycardia (120 bpm) after smoking cannabis while taking imipramine 50mg daily (See reference number 2). Four adolescents aged 15 to 18 taking tricyclic antidepressants for attention-deficit hyperactivity disorder had transient cognitive changes,delirium and tachycardia after smoking cannabis (See reference number 3).

Increased heart rates are well-documented adverse effects of both tricyclic antidepressants and cannabis, and what occurred was probably due to additive beta-adrenergic and antimuscarinic effects of tricyclics, with beta-adrenergic effect of cannabis. Direct information is limited but it has been suggested that concurrent use should be avoided (See reference number 1).

Hillard JR,Vieweg WVR. Marked sinus tachycardia resulting from the synergistic effects ofmarijuana and nortriptyline. Am J Psychiatry (1983) 140, 626–7.

Kizer KW. Possible interaction of TCA and marijuana. Ann Emerg Med (1980) 9,444.

Wilens TE,Biederman J, Spencer TJ. Case study: adverse effects of smoking marijuana whilereceiving tricyclic antidepressants. J Am Acad Child Adolesc Psychiatry (1997) 36, 45–8.