Higher doses of sildenafil impair olfactory function, which is possibly linked to an impairment in nasal airflow that sildenafil can induce, German researchers report in the January issue of The Journal of Urology.

A team led by Dr. V. Gudziol at the University of Dresden Medical School studied 20 healthy, young male volunteers who received 50 mg, 100 mg and placebo in random order in a double-blind, crossover trial.

Subjects smelled odor-dispensing devices (Sniffin' Sticks). The investigators tested odor detection threshold, odor discrimination and odor identification ability.

They found that the 100 mg dose resulted in a decrease in olfactory function, specifically odor discrimination and odor threshold, compared with placebo. The 50 mg dose had no effect on olfactory function.

Genotyping of the intraoral epithelium was done, but genotype had no effect on olfactory function with sildenafil administration.

"In our subjects, the most likely reason for impaired peripheral olfactory function was nasal congestion," the authors write.

They note that, while it was not evaluated in this study, sildenafil is associated with "a significant decrease in nasal inspiratory peak flow," and that some genotypes appear to affect nasal airflow response more than others among elderly subjects but not younger individuals.

J Urology 2007;177:258-261.