Combination of intravenous S-ketamine and oral tranylcypromine in treatment-resistant depression: A report of two cases.

Ketamine, a rapid-acting antidepressant and anti-suicidal agent, is thought to increase brain monoamine levels by enhancing monoamine release or inhibiting presynaptic monoamine-reuptake. Here we present two female inpatients suffering from treatment-resistant depression with recurrent severe suicidal crises receiving a combination of intravenous S-ketamine and oral tranylcypromine, which is a well-known irreversible monoamine oxidase (MAO) inhibitor. Since inhibition of monoamine-reuptake with concurrent blockade of MAO might trigger sympathomimetic crisis, this combination is considered hazardous. Nonetheless, cardiovascular parameters remained stable in both patients, while good anti-suicidal effects were observed. Hence, we put serious doubt on whether monoamine-reuptake inhibition is a relevant pharmacological effect of ketamine in humans.