Background: Sildenafil prolongs the action of cyclic guanosine monophosphate and nitric oxide by inhibiting cyclic guanosine monophosphate-specific phosphodiesterase 5. It is largely used for erectile dysfunction, a highly prevalent condition in obstructive sleep apnea. Because nitric oxide promotes upper airway congestion, muscle relaxation, and pulmonary vasodilation, the aim of this study was to establish the impact of a single 50-mg dose of sildenafil on the sleep of patients with severe obstructive sleep apnea.
Methods: Thirteen [corrected] middle-aged men with severe obstructive sleep apnea were consecutively selected for this double-blind, placebo-controlled, crossover study. Exclusion criteria were obesity, cardiovascular and/or respiratory disease, and conditions that interfere with sleep. All-night polysomnography was preceded by a single 50-mg dose of sildenafil or matching placebo randomly administered at bedtime, after a washout period of 1 week.
Results: In comparison to placebo, a single 50-mg dose of sildenafil significantly increased the percentage of total sleep time with an arterial oxygen saturation of less than 90% (mean +/- SD, 15.6% +/- 9.6% vs 7.9% +/- 3.3%, [corrected] P < .01), without a difference in the nadir of oxygen desaturation. The mean arterial oxygen saturation also decreased (92.1% +/- 1.9% vs 93.8% +/- 1.3%, P = .03), [corrected] and the desaturation index increased (30.3 +/- 14.5 [corrected] events per hour vs 18.5 +/- 9.1 [corrected] events per hour, P < .001). There was an increase in apnea-hypopnea index (48.1 +/- 20.8 [corrected] events per hour vs 32.3 +/- 11.3 [corrected] events per hour, P = .001), [corrected] involving mostly obstructive events.
Conclusion: In patients with severe obstructive sleep apnea, a single 50-mg dose of sildenafil at bedtime worsens respiratory and desaturation events.