Drug Interactions between imipramine and isoniazid

Consumer information for this interaction is not currently available.

GENERALLY AVOID: Coadministration of isoniazid (INH), with drugs that possess serotonergic activity (e.g., serotonin reuptake inhibitors, 5-HT1 receptor agonists, ergot alkaloids, etc.) may increase the risk of serotonin syndrome, a rare but serious and potentially fatal condition. The proposed mechanism is an increase in serotonin resulting from INH's weak inhibition of monoamine oxidase (the enzyme primarily responsible for breaking down norepinephrine, serotonin, and dopamine) combined with the increase in serotonin from the serotonergic drug(s). In one case report, a patient taking mirtazapine (15 mg nightly) for depression was started on INH (300 mg daily) and pyridoxine (25 mg daily) for tuberculosis prophylaxis following a liver transplant from a donor with latent tuberculosis. Six days following the initiation of INH, the patient developed symptoms consistent with serotonin syndrome (e.g., diarrhea, nausea, tremors, hypertension, and altered mental status) which resolved upon the cessation of INH and mirtazapine. However, consensus on the safety of concomitant use of isoniazid with drugs possessing serotonergic activity is lacking and most of the existing data are limited to case reports.

MANAGEMENT: Until more information is available, coadministration of isoniazid with drugs that possess serotonergic activity (e.g., serotonin reuptake inhibitors, 5-HT1 receptor agonists, ergot alkaloids, etc.) should generally be avoided. If coadministration with a serotonergic drug is required, patients should be advised to promptly seek medical attention if they experience signs and symptoms of serotonin syndrome (including but not limited to confusion, hallucinations, tachycardia, hyperthermia, diaphoresis, shivering, blood pressure lability, neuromuscular abnormalities and/or unexplained gastrointestinal symptoms).