Nasal administration of the nitric oxide synthase inhibitor L-NAME induces daytime somnolence.

In preliminary studies, human subjects complained of drowsiness after aerosolization of NG-nitro-L-arginine methyl ester (L-NAME) into the nasal passages. We compared the effects of a nasal aerosol of L-NAME (0.5 M, 4 ml) to those of saline on sleep onset latency and exhaled nasal nitric oxide (NO). L-NAME decreased sleep onset latency and exhaled nasal NO. Vasoconstriction and local effects of L-NAME on NO synthesis are unlikely to explain this effect since oxymetazoline, a vasoconstrictor, decreased exhaled NO but had no effect on sleep onset latency. We conclude that aerosolization of L-NAME to the nasal passages induces daytime sleepiness.