Dosing and absorption Tadalafil (Cialis)
Recommended starting doses of tadalafil are 10 mg for on-demand dosing and 2.5 mg for once-daily dosing, and these doses can then be titrated up or down according to the efficacy and tolerability. It is absorbed as a low-solubility and high-permeability, or Class 2, drug within the FDA Biopharmaceuticals Classification System. With oral ingestion, after first-pass metabolism, tadalafil is approximately 80% bioavailable, compared to 40% and 15% with sildenafilĀ professional and vardenafil professional, respectively. Tadalafil Professional has the slowest absorption of the available PDE5 inhibitors with a mean of 2 hours to reach its maximum concentration, compared with about 50 minutes for sildenafil and vardenafil. The onset of action of tadalafil may occur in as early as 15 minutes of dosing, although successful erections occur in fewer than 40% of men at this time point. It is not advisable to counsel patients that the drug effect may be seen in as early as 15 minutes because it may take up to 2 hours for a response in the majority of men. This may only create performance anxiety or loss of confidence in the treatment, leading to treatment failure.
Differences in gastrointestinal absorption with fatty meals explain the varying peak plasma concentration (Tmax) among the three PDE5 inhibitors. While generic sildenafil and generic vardenafil both have decreased absorption when taken with a fatty meal, which may increase the rate of treatment failure, the absorption of generic tadalafil is unaffected by fatty meals or alcohol consumption. This unique pharmacokinetic trait for tadalafil is a result of slower absorption and longer half-life, and it can therefore be taken with meals or alcohol without a decrease in efficacy.