Viagra is manufactured by Pfizer Inc. However there are a few licensed pharmaceutical corporations outside of the United States that manufacture and sell generic Viagra, which contains absoulutly the same active ingredient of brand Viagra (Sildenafil) and it acts exactly as the more expensive brand version does.
The mechanism of action of Viagra involves the release of nitric oxide (NO) in the corpus cavernosum of the penis. Viagra is metabolised by liver enzymes and excreted by both kidneys and the liver.
Viagra dosage
Viagra comes in three doses: 25, 50 and 100 milligrams (mg).
Each body may respond in a different way to medications, and so if a 25 mg pill works perfectly for someone, that doesn't mean it will work the same way for everybody. Usually your pharmacist will ask you to start with a low dosage (25 or 50 mg) and see how effective it is. If the low dosage doesn't give you the results you can try a higher dosage and see how that goes. Following your doctor's directions should give you the best results.
Most men who use Viagra say that the 50 mg pill works the best for them. You must know, that increasing the dosage of Viagra doesn't always mean better results. If the 50 mg Viagra dose gives you good results, you may not notice any difference if you switch to a higher dosage.
You may save some money, if you purchase 100 mg Viagra and just cut the pills into two halves.
Viagra side effects:
Do not use VIAGRA if you are using nitrates, often prescribed against chest pain, as this may cause a drop in blood pressure.
Seek for a medical help to avoid long-term injury, as with any ED tablet, in the rare event of an erection lasts for more than 4 hours.
Use Viagra with care if you have serious kidney or liver problems or you are older than age 65. If you are taking protease inhibitors, your pharmacist may recommend a 25-mg dose and may limit you to a maximum single dose of 25 mg of VIAGRA within a 48-hour period.
If you use alpha blockers to treat prostate problems or high blood pressure your pharmacist may start you on a lower dose of VIAGRA.
VIAGRA will not protect you against sexually transmitted diseases, including HIV.
The most common side effects of VIAGRA are facial flushing, headache and upset stomach. Less commonly, blurred vision, bluish vision, or even sensitivity to light may briefly occur.
