Common uses of Viagra

• Generic Viagra is used to treat erection difficulties, such as erectile dysfunction (ED).

What is Viagra?

• Sildenafil citrate, sold under the names Viagra, Revatio and under various other names, is a drug used to treat male erectile dysfunction (impotence) and pulmonary arterial hypertension (PAH), developed by the pharmaceutical company Pfizer.
• Sildenafil under the name Viagra is used to treat erectile dysfunction (impotence) in men. Sildenafil is a potent and selective inhibitor of cGMP specific phosphodiesterase type 5 (PDE5) which is responsible for degradation of cGMP in the corpus cavernosum.
• Sildenafil may also be used for purposes other than those listed here.

History

• Viagra was synthesized by a group of pharmaceutical chemists working at Pfizer's Sandwich, Kent research facility in England. It was initially studied for use in hypertension (high blood pressure) and angina pectoris (a symptom of ischaemic cardiovascular disease).
• The first clinical trials were conducted in Morriston Hospital in Swansea. Phase I clinical trials under the direction of Ian Osterloh suggested that the drug had little effect on angina, but that it could induce marked penile erections.
• The drug was patented in 1996, approved for use in erectile dysfunction by the Food and Drug Administration on March 27, 1998, becoming the first pill approved to treat erectile dysfunction in the United States, and offered for sale in the United States later that year.

What should I know before I take Viagra?

• Generic Viagra comes as a tablet containing 100 mg. sildenafil citrate, to take by mouth.
  
• For most men, the recommended dose is 50 mg. taken, as needed, approximately 1 hour before sexual activity. However, sildenafil citrate may be taken anywhere from 4 hours to 0.5 hour before sexual activity.
• Based on effectiveness and toleration, the dose may be increased to a maximum recommended dose of 100 mg or decreased to 25 mg. The maximum recommended dosing frequency is once per day.

Precautions

• A starting dose of 25 mg. should be considered individuals of the age 65+ and in individuals with hepatic impairment or severe renal impairment.
  Given the extent of the interaction with patients receiving concomitant therapy with ritonavir, it is recommended not to exceed a maximum single dose of 25 mg. of Generic Viagra in any 48 hour period.
• Sildenafil citrate potentiates the hypotensive effects of nitrates and its administration in patients who use nitric oxide donors or nitrates in any form is therefore contraindicated.
• Treatments for erectile dysfunction, including Generic Viagra, should not be generally used in men for whom sexual activity is inadvisable because of their underlying cardiovascular status.
• Patients who have suffered a myocardial infarction, stroke, or life-threatening arrhythmia within the last 6 months, patients with resting hypotension or hypertension, patients with cardiac failure or coronary artery disease and patients with retinitis pigmentosa should use Generic Viagra with great caution.
• The safety of Generic Viagra is unknown in patients with bleeding disorders and patients with active peptic ulceration.
• Generic Viagra should be used with caution by individuals with anatomical deformation of the penis and by individuals who have conditions which may predispose them to priapism.
• The safety and efficacy of combinations of Generic Viagra with other treatments for erectile dysfunction have not been studied. Therefore, the use of such combinations is not recommended.

How Viagra works?

• Sildenafil is a potent and selective inhibitor of cGMP specific phosphodiesterase type 5 (PDE5) which is responsible for degradation of cGMP in the corpus cavernosum. The molecular structure of sildenafil is similar to that of cGMP and acts as a competitive binding agent of PDE5 in the corpus cavernosum, resulting in more cGMP and better erections. Without sexual stimulation, and therefore lack of activation of the NO/cGMP system, sildenafil should not cause an erection. Other drugs that operate by the same mechanism include tadalafil (Cialis) and vardenafil (Levitra).