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.
Fourteen 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.
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, 14.2% ± 9.1% vs 8.5% ± 3.2%, P<.01), without a difference in the nadir of oxygen desaturation. The mean arterial oxygen saturation also decreased (92.1% ± 1.91% vs 93.8% ± 1.3%, P = .02), and the desaturation index increased (30.3 ± 18.1 events per hour vs 18.5 ± 14.6 events per hour, P<.001). There was an increase in apnea-hypopnea index (42.4 ± 25.5 events per hour vs 34.6 ± 24.1 events per hour, P = .01), involving mostly obstructive events.
In patients with severe obstructive sleep apnea, a single 50-mg dose of sildenafil at bedtime worsens respiratory and desaturation events.