Introduction. Several phosphodiesterase type 5 (PDE5) inhibitors are commercially available for the treatment of erectile dysfunction (ED). Development of the first once-daily alternative dosing regimen with a PDE5 inhibitor was motivated by the behavioral complexities associated with sexual intimacy.
Aim. To provide an alternative dosing option for certain men who may benefit from the removal of the temporal linkage between administration of an ED therapy and sexual intimacy or for men and their partners who anticipate at least twice-weekly sexual activity.
Methods. Pharmacokinetic predictions of tadalafil plasma concentrations were generated based upon empirical data following 20-mg, single-dose administration coupled with tadalafil usage patterns from as-needed clinical trials. To support the pharmacokinetic simulations and pharmacodynamic assumptions, clinical trials were conducted to demonstrate the efficacy and safety of once-daily, low-dose tadalafil 2.5 and 5 mg.
Main Outcome Measures. Simulated tadalafil plasma concentrations and comparison with safety and efficacy measures from clinical trials.
Results. Based upon pharmacodynamic and pharmacokinetic data, once-daily doses of tadalafil 5 mg were predicted to provide therapeutic concentrations that would be maintained throughout the 24-hour dosing interval. Additionally, for a subgroup of men who anticipate at least twice-weekly sexual activity and are currently taking tadalafil 20 mg, a reduction in daily tadalafil exposure was predicted. To support the hypothesis that low-dose, once-daily tadalafil may be a safe and effective treatment alternative, clinical trials were conducted to demonstrate the safety and efficacy of once-daily tadalafil 2.5 and 5 mg. These results were similar to those of historical as-needed studies evaluating tadalafil 10 and 20 mg.
Conclusions. Consistent with pharmacokinetic predictions, data from clinical trials indicate that once-daily use of low-dose tadalafil is a safe and effective treatment for men with ED. Wrishko R, Sorsaburu S, Wong D, Strawbridge A, and McGill J. Safety, efficacy, and pharmacokinetic overview of low-dose daily administration of tadalafil. J Sex Med 2009;6:2039–2048.