Tadalafil inhibits the enzyme phosphodiesterase-5, which delays the breakdown of the neurotransmitter cGMP. This in turn triggers a relaxation of the smooth muscle in the penis, causing the blood vessels to dilate and allowing more blood to flow into the corpus cavernosum. As a result, an erection can be produced or maintained longer and stronger.
The drug also causes the smooth muscle of the pulmonary vessels to relax, lowering blood pressure in the pulmonary arteries.
In benign enlargement of the prostate, tadalafil reduces smooth muscle cell growth, helping to reduce prostate size and relieve symptoms.
The maximum plasma concentration of tadalafil is reached after approximately 2 hours and is 94% bound to plasma proteins. The half-life is 15-17.5 hours. In the liver, the drug is metabolized by the enzyme CYP3A4 and excreted mainly in the stool and 30% in the urine.
Since tadalafil enhances the antihypertensive effects of nitrates, NO donors, amyl nitrite, and other antihypertensive agents, the agents should not be used concomitantly.
Mit Arzneimitteln die auch durch das CYP3A4 abgebaut werden, können ebenfalls Wechselwirkungen auftreten.