Safety of Ketamine Augmentation to Monoamine Oxidase Inhibitors in Treatment-Resistant Depression

Objective: Ketamine is increasingly prescribed for treatment-resistant depression (TRD), often as add-on to regular antidepressants. Augmentation of ketamine to monoamine oxidase inhibitors (MAOIs) is advised against, as this practice might increase blood pressure or cause serotonin syndrome. Despite the potential relevance for patients, little is known about actual side effects of combined use. We summarize literature on the safety and add results of our case series. Evidence Review: PubMed and Embase were searched from inception to July 2021 for English-language articles describing concomitant use of ketamine and MAOIs. The search strategy included terms for "ketamine" AND "monoamine oxidase inhibitor" including generic and brand names. Additionally, we describe the safety of twice weekly oral esketamine administration over the course of 5 weeks to 9 months in 8 TRD patients using MAOIs. Findings: After deduplication, we screened 138 articles and assessed 43 full texts. Twelve studies were included with a total of 39 patients receiving ketamine and MAOIs. Blood pressure and heart rate increased in multiple cases, though this was deemed clinically insignificant in all but 1 patient. No signs of hypertensive crisis or serotonin syndrome were observed. In our case series, we observed minor elevations in blood pressure and heart rate and no serious adverse events. Conclusions and Relevance: The results suggest that combined use of MAOIs and esketamine is less prone to severe side effects than presumed. The investigated sample size was small, and prescribed doses of MAOIs were relatively low. Further research is required before definite conclusions about the safety of this combination can be drawn.