Abstract
Pharmacokinetics and bioavailability of a chewable tablet formulation of sildenafil citrate 100 mg developed using taste-masking technology and taken with or without water (chewed until full disintegration and then swallowed) versus the conventional film-coated sildenafil tablet (Viagra ® ) taken with water were evaluated in the fasted state in a randomized, open-label, single-dose, 3-period crossover study in 30 healthy men aged 18 to 40 years (mean ± SD, 24±4 y). Sildenafil plasma concentrations were determined using a validated high-performance liquid chromatography method with ultraviolet detection. Bioequivalence criteria were 90% classic and Westlake CIs within 80% to 125% for test/reference ratios; limit tests applied were Schuirmann unilateral double t test and the Anderson-Hauck test. For area under the curve (AUC), bioequivalence criteria were met for all the treatments studied. For maximum plasma concentration (C max ), bioequivalence criteria were met for the chewable tablet with water relative to Viagra when using the Westlake CI. The chewable tablet without water had equivalent AUC, but the C max was up to 22% lower when compared with Viagra or with the chewable tablet with water. Median time to C max was lowest for the chewable tablet with water (0.75 h) versus Viagra (1.0 h) or the chewable tablet without water (1.75 h). Adverse events with the chewable tablet were consistent with the tolerability profile of Viagra. Only 1 (3%, chewable tablet with water) and 4 (13%, chewable tablet without water) subjects reported bitter taste, demonstrating successful taste masking.
Highlights
Sildenafil citrate is a phosphodiesterase type 5 inhibitor
Mean sildenafil plasma concentration versus time profiles were nearly superimposable for Viagra and the chewable tablet taken with water; the chewable tablet taken without water resulted in a somewhat slower absorption rate, as indicated by lower Maximum plasma concentration (Cmax) compared with the chewable tablets or Viagra taken with water (Figure 1)
Median Time to reach Cmax (Tmax) was lowest for the chewable tablet taken with water (0.75 h) compared with Viagra (1.0 h) or the chewable tablet taken without water (1.75 h) (Table 1)
Summary
Sildenafil citrate is a phosphodiesterase type 5 inhibitor. In countries worldwide, including Mexico, sildenafil citrate is approved for the treatment of erectile dysfunction as conventional film-coated tablets of 50-mg and 100-mg strengths for oral administration with water (Viagra®, Pfizer Inc, New York, NY). Viagra is rapidly absorbed, reaching a mean maximum plasma concentration (Cmax) of 514 ng/mL within 30 to 120 minutes (median, 60 min) after oral administration of the 100-mg dose in the fasted state [1]. Mean terminal half-life (t1⁄2) is approximately 4 hours [1]. Across the range of 25–200 mg, a small and clinically insignificant degree of non-proportionality was observed in predicted increases in Cmax (2.1fold) and in area under the plasma concentration versus time curve (AUC, 2.2-fold) [1]
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