Different antimuscarinics when combined with atomoxetine have differential effects on obstructive sleep apnea severity.

The combination of the noradrenergic agent atomoxetine plus the anti-muscarinic oxybutynin has recently been shown to improve upper airway physiology and reduce obstructive sleep apnea (OSA) severity. However, the effects of different anti-muscarinics when combined with atomoxetine is limited. This study aimed to determine the effects of atomoxetine combined with two different anti-muscarinics with varying M-subtype receptor selectivity on OSA severity and upper airway physiology.10 people with predominantly severe OSA completed a double-blind, randomised, placebo-controlled, cross-over trial. Participants completed 3 overnight in-laboratory sleep studies after either 80mg atomoxetine+5mg solifenacin succinate (ato-sol) or 80mg atomoxetine+2mg biperiden hydrochloride (ato-bip) or placebo. OSA severity, ventilatory stability (loop gain), respiratory-arousal threshold (via epiglottic manometry), next day subjective sleepiness (Karolinska Sleepiness Scale:KSS) and alertness were compared between conditions. Neither drug combination altered the apnea/hypopnoea index versus placebo (p=0.63). Ato-sol caused a shift towards milder respiratory events with reduced frequency of obstructive apneas (13±14vs. 22±17events/h; mean±SD, p=0.04) and increased hypopneas during NREM (38±21vs. 24±18events/h, p=0.006) with improved nadir oxygenation versus placebo (83±4vs. 80±8%, p=0.03). Both combinations reduced loop gain by ~10% versus placebo; sleep efficiency and arousal threshold were unaltered. Ato-bip reduced next-day sleepiness versus placebo (KSS=4.3±2.2vs. 5.6±1.6, p=0.03).Atomoxetine+biperiden hydrochloride reduces perceived sleepiness and atomoxetine+solifenacin modestly improves upper airway function in people with OSA but to a lesser extent versus recently published atomoxetine+oxybutynin (broad M-subtype receptor selectivity) findings. These results provide novel mechanistic insight into the role of noradrenergic and anti-muscarinic agents on sleep and breathing and are important for pharmacotherapy development for OSA.