Sildenafil, also known as Viagra is one of a group of medicines that delay enzymes called phosphodiesterases from working too quickly, and is used to treat men who have erectile dysfunction.
By controlling these enzymes Viagra helps men maintain an erection. Viagra is also used to treat the symptoms of pulmonary arterial hypertension. Viagra helps by increasing the supply of blood to the lungs and reducing the workload of the heart.
Be sure to tell your doctor of any allergies you have whether it is to medication or food, preservatives, or dyes. Also tell your doctor of any other medications you are taking, including vitamins and supplements, and any medical conditions you may have.
It is very important that you take this medicine exactly as and only as your doctor tells you to. Do not take more than directed.
If taken daily for Pulmonary Arterial Hypertension and you miss a dose, take it as soon as you remember, unless it is almost time for your next dose. If that is the case, skip that dose and return to your usual schedule. Do NOT double doses.
Tell your doctor immediately if you notice any of the following: abnormal vision, including blurred vision, seeing shades of colors differently than before, or sensitivity to light; bladder pain; burning, crawling, itching, numbness, prickling, “pins and needles”, or tingling feelings; burning feeling in chest or stomach; cloudy or bloody urine; dizziness; increased frequency of urination; indigestion; pain on urination; stomach upset; tenderness in stomach area; bleeding of the eye; convulsions; decreased vision or other changes in vision; double vision; prolonged, painful, or inappropriate erection of penis; redness, burning, or swelling of the eye; or vision loss.
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 (sildenafil citrate) is formulated as blue, film-coated rounded-diamond-shaped tablets equivalent to 25 mg, 50 mg and 100 mg of sildenafil for oral administration. In addition to the active ingredient, sildenafil citrate, each tablet contains the following inactive ingredients: microcrystalline cellulose, anhydrous dibasic calcium phosphate, croscarmellose sodium, magnesium stearate, hypromellose, titanium dioxide, lactose, triacetin, and FD & C Blue #2 aluminum lake.
Viagra has the following structural formula: