Tadalafil Selective Reversible Inhibitors


Tadalafil, is a selective reversible inhibitor of cyclic guanosine monophosphate (cGMP)-specific phosphodiesterase 5(PDE5). When sexual stimulation leads to the local release of nitric oxide, PDE5 is inhibited by tadalafil, which increases cGMP levels in the corpus cavernosum, which leads to smooth muscle relaxation, blood flow into the penile tissue, and erection; if there is no sexual stimulation, the drug may not play its role.
It is rapidly absorbed after oral administration, and the mean maximum observed plasma concentration (cmax) is reached by a median time of 2 hours after administration. The absolute bioavailability of this product after oral administration is not known. The absorption rate and degree of tadalafil are not affected by food, so this product can be taken with or without food. The time of administration (morning or evening) had no clinically significant effect on the rate and extent of absorption, with an average volume of about 63 liters, indicating that tadalafil was distributed into the tissues. At therapeutic concentrations, 94% of tadalafil in plasma is bound to protein. Protein binding was not affected by renal impairment. In healthy subjects, the average clearance rate of oral tadalafil is 2.5L/hr, and the average half-life is 17.5 hours. Tadalafil is mainly excreted in the form of inactive metabolites, mainly from feces (about 61% of the dose), and a small part is excreted in urine (about 36% of the dose).