Viagra, an oral therapy for erectile dysfunction, is the citrate salt of sildenafil, a selective inhibitor of cyclic guanosine monophosphate (cGMP)-specific phosphodiesterase type 5 (PDE5).
•Sildenafil citrate is designated chemically as 1-[[3-(6,7-dihydro-1-methyl-7-oxo-3-propyl-1H-pyrazolo[4,3-d]pyrimidin-5-yl)-4-ethoxyphenyl]sulfonyl]-4-methylpiperazine citrate.
• Sildenafil citrate is a white to off-white crystalline powder with a solubility of 3.5 mg/ml in water and a molecular weight of 666.7. Viagra is formulated as blue, film-coated rounded-diamond-shaped tablets equivalent to 25 mg, 50 mg and 100 mg of sildenafil for oral administration.
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Sildenafil (sil-DEN-a-fil) belongs to a group of medicines that delay the enzymes called phosphodiesterases from working too quickly. The penis is one of the areas where these enzymes work. Sildenafil is used to treat men who have erectile dysfunction (also called sexual impotence).
By controlling the enzyme phosphodiesterase, sildenafil helps to maintain an erection that is produced when the penis is stroked. Without physical action to the penis, such as that occurring during sexual intercourse, sildenafil will not work to cause an erection.
•Adults up to 65 years of age•
50 mg as a single dose no more than once a day, 1 hour before sexual intercourse. Alternatively, the medicine may be taken 30 minutes to 4 hours before sexual intercourse. If needed, your doctor may increase your daily dose to 100 mg or decrease your daily dose to 25 mg.
•Adults 65 years of age and older•
25 mg as a single dose no more than once a day, 1 hour before sexual intercourse. Alternatively, the medicine may be taken 30 minutes to 4 hours before sexual intercourse. If needed, your doctor may increase your daily dose.
• If you are taking protease inhibitors•
Such as for the treatment of HIV, your doctor may recommend a 25 mg dose and may limit you to a maximum single dose of 25 mg of Viagra in a 48 hour period.
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Note: Though new erectile dysfunction and impotence treatment options as well as medicines have recently emerged, sildenafil citrate, the active ingredient in viagra continues to produce excellent results in the treatment of sexual dysfunction.
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