Tadalafil

Tadalafil is rapidly absorbed when taken orally. After ingestion of a single dose Tmax ranges from 30 min to 6 h (average 2 hours), the absolute bioavailability not determined. The rate and extent of absorption do not depend on food intake.

Middle seeming volume of distribution after a reception inward is approximately 63 litres, indicating that tadalafil is distributed into tissues. At therapeutic concentrations 94% of tadalafil bound to plasma proteins.

In healthy persons less than 0.0005% of the dose was found in semen.

In healthy volunteers increased AUC of tadalafil proportionally with the dose in the dose range of 2.5–20 mg Equilibrium concentration is achieved within 5 days when taken daily 1 time per day, with AUC of around 1.6 times greater than when a single dose.

Tadalafil is predominantly metabolized by CYP3A4 to a catechol that undergoes methylation and glukuronirovaniu with the formation of methylcatechol and methylcatechol conjugate with glucuronide, respectively. The main circulating metabolite — methylethanolamine, the concentration of methylcatechol is less than 10% that of the glucuronide. In vitro data suggests that metabolites in the observed concentration does not have pharmacological activity.

Oral clearance of tadalafil is 2.5 l/HR, terminal T1/2 is 17.5 hours in healthy volunteers. Tadalafil is excreted predominantly as metabolites, mainly with feces (about 61% of the dose) and to a lesser extent from the urine (approximately 36%).

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