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Author: Admin | 2025-04-28
PDE5 inhibitors in patients with retinitis pigmentosa, an eye condition that affects the retina and can cause blindness, so caution is recommended if you have this health condition.Sildenafil (Viagra)What is sildenafil (Viagra)?Sildenafil (Viagra) was the first oral phosphodiesterase type 5 (PDE5) inhibitor approved by the FDA in the United States for the treatment of erectile dysfunction (it is not approved for women). Sildenafil inhibits PDE5, which is an enzyme that destroys cGMP. By inhibiting the destruction of cGMP by PDE5, sildenafil allows cGMP to accumulate. The cGMP in turn prolongs the relaxation of the smooth muscle of the corpora cavernosa. Relaxation of the corpora cavernosa smooth muscle allows blood to flow into the penis resulting in increased engorgement of the penis. In short, sildenafil increases blood flow into the penis and decreases blood flow out of the penis.How effective is sildenafil (Viagra)?Sildenafil treats erectile dysfunction of either physical or psychological causes. It is effective in treating erectile dysfunction in men with coronary artery disease, diabetes mellitus, hypertension, depression, coronary artery bypass grafting (CABG), and men who are taking antidepressants and several classes of antihypertensives.In randomized placebo-controlled trials, an estimated 60% of men with diabetes, and 80% of men without diabetes experienced improved erections with sildenafil.How do patients take sildenafil (Viagra)?Sildenafil is available as oral tablets at doses of 25 mg, 50 mg, and 100 mg. Patients should take sildenafil approximately one hour before sexual activity. In some men, the onset of action of the drug may be as early as 11-20 minutes. Men should take sildenafil on an empty stomach for best results since absorption and effectiveness of sildenafil can be diminished if it is taken shortly after a meal, particularly a meal that is high in fat. Sildenafil and the other PDE5 inhibitors don't cause an immediate erection. Sexual stimulation is necessary for these medications to work.What is the dose of sildenafil (Viagra)?In prescribing sildenafil, a doctor considers the age, general health status, and other medication(s) the patient is taking. The usual starting dose for most men is 50 mg, however, the doctor may increase or decrease the dose depending on side effects and effectiveness. The maximum recommended dose is 100 mg every 24 hours. However, many men will need 100 mg of sildenafil for optimal effectiveness, and some doctors are recommending 100 mg as the starting dose.Aging, liver and kidney problems and concurrent use of certain medications (such as erythromycin [an antibiotic] and protease inhibitors for HIV) slow the metabolism (breakdown) of sildenafil. Slowed breakdown allows sildenafil to accumulate in the body and potentially may increase the risk of side effects. Therefore, in men over 65 years of age, men with significant kidney and liver disease, and men who also are taking medications called protease inhibitors, the doctor will initiate sildenafil at a lower dose (25 mg) to avoid the accumulation of sildenafil in the body. A protease inhibitor ritonavir (Norvir) is especially potent in increasing the accumulation of sildenafil, thus men who are taking Norvir should not
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