Two randomized placebo-controlled trials to evaluate the efficacy and tolerability of mirtazapine for the treatment of obstructive sleep apnea

Objective: Mirtazapine is an α_2A antagonist and mixed 5-HT₂/5-HT₃ antagonist that has been proposed as a potential treatment for obstructive sleep apnea (OSA). A small, randomized, controlled trial has previously found an approximate halving in the severity of OSA with daily doses of 4.5 and 15 mg. We aimed to confirm and extend these findings in 2 randomized placebo-controlled, proof-of-concept trials. Methods: Two randomized, double-blind, placebo-controlled trials of mirtazapine for OSA (apnea-hypopnea index 10-40/h). Study 1: 3-way crossover, dose-finding study testing the self-administration of mirtazapine (7.5, 15, 30, and/or 45 mg) or placebo 30 minutes prior to bedtime for 2 weeks at each dose. Twenty patients were randomly assigned to 1 of 6 different dose-sequence groups, with each patient exposed to a maximum of 3 doses. Study 2:3-arm, randomized, parallel-group trial of mirtazapine at 15 mg or mirtazapine 15mg + Compound CD0012 or placebo for 4 weeks in 65 patients with OSA. Results: Two patients withdrew from Study 1 after complaints of unacceptable lethargy. Fifteen patients were withdrawn from study 2, 7 after complaints of unacceptable lethargy or other side-effects. No measurement of sleep apnea improved due to mirtazapine in either study. Weight gain was significantly greater on mirtazapine than on placebo in both trials. Conclusions: Mirtazapine did not improve sleep apnea in either trial. Mirtazapine caused weight gain, which may further worsen OSA. Therefore, mirtazapine is not recommended for the treatment of OSA.