Comparison of the solubility and pharmacokinetics of sildenafil salts.

To develop sildenafil lactate, a salt form of sildenafil with improved solubility and bioavailability of poorly water-soluble sildenafil base, this salt form was prepared using a spray dryer. Its solubility and pharmacokinetics in rabbits were evaluated compared with sildenafil base and sildenafil citrate. Sildenafil lactate improved the solubility of sildenafil in various solvents including distilled water compared with sildenafil citrate. It provided higher AUC and C(max) and, shorter t(1/2) values than did the other materials, indicating that it improved the oral bioavailability of sildenafil in rabbits. Our results suggest that sildenafil lactate would be useful to deliver sildenafil in a pattern that allows fast absorption and late metabolism. Furthermore, the plasma concentration at 0.25 h in sildenafil lactate was similar to the C(max) value at T(max) (0.5 h) in sildenafil citrate. Thus, sildenafil lactate might provide a faster onset of action and immediate erection compared with sildenafil citrate, the conventional drug.