NEW YORK (Reuters Health) — Higher doses of Viagra (sildenafil) may impair the ability to smell, which is possibly related to an increase in nasal congestion, German researchers report in 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 Viagra, at a 50- or 100-mg dose, or inactive “placebo” and then were exposed to an odour-dispensing device. The researchers tested the subjects’ odour detection threshold, odour discrimination and odour identification ability. They found that the 100-mg dose caused a drop in smelling or “olfactory” ability, specifically odour discrimination and odour threshold, compared with placebo. The 50-mg dose, by contrast, had no effect on olfactory function.