Population pharmacokinetic analysis of data from patients in clinical trials indicated approximately 3-fold the sildenafil clearance when it was co-administered with mild CYP3A inducers. Also, the number of doses you take each day, the time allowed between doses, and the length of time you take the medicine depend on the medical problem for which you are using the medicine. For all other alpha-blockers, tadalafil should be used with caution; treatment should be initiated at the minimum dose and progressively adjusted. The result of smooth muscle cell target protein phosphorylation is a decrease in intracellular calcium, increased efflux of potassium, and deactivation of myosin light chain kinase, ultimately causing smooth muscle relaxation. Sexual activity may be a strain on your heart, especially if you have heart disease. Continue to take sildenafil even if you feel well. · Sildenafil is used to treat men who have erectile dysfunction (also called sexual impotence). Sildenafil belongs to a group of medicines called phosphodiesterase . Sildenafil comes as a tablet and suspension (liquid) to take by mouth. If you are taking sildenafil to treat erectile dysfunction, follow your doctor’s directions and the guidelines . Sildenafil should be used with caution in men taking an alpha-blocker (especially doxazosin). Hypotension is more likely to occur within four hours following treatment with .