Sildenafil, also known as Viagra, is a medication used to treat erectile dysfunction (ED) and pulmonary arterial hypertension (PAH). It works by relaxing the muscles in the walls of blood vessels, which increases blood flow to certain areas of the body, such as the penis or lungs.
Sildenafil is classified as a phosphodiesterase type 5 (PDE5) inhibitor, which means it blocks the action of PDE5 enzymes. These enzymes break down cyclic guanosine monophosphate (cGMP), a molecule that relaxes smooth muscle cells and increases blood flow. By blocking PDE5, sildenafil increases cGMP levels, which helps to relax the smooth muscle cells in the blood vessels and increase blood flow to the penis or lungs.
In the treatment of ED, sildenafil is typically taken as needed, about 30 minutes to one hour before sexual activity. The recommended starting dose is 50 mg, but the dose may be adjusted based on individual response and tolerance, up to a maximum dose of 100 mg. Sildenafil should not be taken more than once per day.
In the treatment of PAH, sildenafil is taken three times per day, with or without food. The recommended dose is 20 mg three times per day, but the dose may be adjusted based on individual response and tolerance, up to a maximum dose of 80 mg per day.
Sildenafil is available in a tablet form in various strengths, including 25 mg, 50 mg, and 100 mg. It should be taken with a full glass of water and swallowed whole, without crushing or breaking the tablet.
Sildenafil may cause side effects, including headache, flushing, upset stomach, and nasal congestion. These side effects are usually mild and go away within a few hours. However, in rare cases, sildenafil may cause more serious side effects, such as sudden vision loss or hearing loss, chest pain, or an erection that lasts more than four hours (priapism). Patients should seek medical attention immediately if they experience any of these symptoms.
Sildenafil may interact with certain medications, including nitrates, alpha-blockers, and blood pressure medications. Patients should inform their healthcare provider of all medications they are taking before starting sildenafil.
In summary, sildenafil is a PDE5 inhibitor medication used to treat ED and PAH. It works by relaxing the muscles in the walls of blood vessels, which increases blood flow to certain areas of the body. Sildenafil is available in tablet form in various strengths and should be taken as directed by a healthcare provider. Patients should be aware of potential side effects and medication interactions and should seek medical attention immediately if they experience any unusual symptoms.