Viagra is indicated for the exclusive treatment of erectile dysfunction.

What are the dosages available for Viagra and how is the drug administered?
For most patients using Viagra for the first time, the recommended dose is – except stated otherwise by one’s doctor – to be taken approximately 1 hour before sexual activity.

However, Viagra tablets could be taken anywhere from 30 minutes to 4 hours before engaging in sexual activity. The dose could be increased to a maximum recommended dose of 100 mg or decreased to 25 mg, based on effectiveness and toleration. The maximum recommended dose is once daily.

The following factors are believed to increase the plasma levels of Sildenafil Citrate (the active ingredients in Viagra):
• Men who are older than 65
• hepatic impairment (e.g., liver cirrhosis)
• Severe impairment of the kidney
• Concomitant use of potent cytochrome P450 3A4 inhibitors (ketoconazole, itraconazole, erythromycin and saquinavir ).

Since higher plasma levels of Viagra are believed to increase both the efficiency and incidence of adverse events of the drug, a starting dose of 25 mg are normally recommended among these patients.

In a study of healthy, non-HIV infected volunteers, Ritonavir was shown to greatly increase the systemic level of sildenafil by about 11-fold increase. Based on these pharmacokinetic data, a maximum single dose of 25 mg of Viagra tablets are recommended for patients using the drug in a 48 hour period.

Viagra is contraindicated for use with nitric oxide donors or nitrates after it was shown that the magic pills potentiate the hypotensive effects of nitrates.

In addition, administration of Viagra tablets in doses above 25 mg simultaneously with an alpha-blocker could lead to symptomatic hypotension in some patients. Doses of 50 mg or 100 mg of Viagra are not to be taken within 4 hours of taking alpha-blockers. However, a 25 mg dose of Viagra tablets could be taken at any time.

Safety information on Viagra
Viagra tablets should not be taken in combination with nitrates, which are usually prescribed for chest pain, as this could lead to a sudden, unsafe drop in blood pressure.

In ensuring that you are healthy enough to engage in sexual activity, discuss your general health status with your doctor. If you experience chest pain or any other discomforts during a Viagra-induced sex, ensure to seek immediate medical help.

In the rare event of an erection lasting more than 4 hours, as with any other ED tablet, seek medical help immediately to avoid long-term injury.

Any man older than 65, or who has serious liver or renal problems, may be started on the lowest dose of 25 mg of Viagra tablets online.

Also, any patient who is taking protease inhibitors, e.g. for the treatment of HIV, may be recommended a 25-mg dose by his doctor and may even be limited to take the single dose in a 48-hour period.

It has been reported that in rare occasions, men taking PDE5 inhibitors (such as Viagra, Cialis, Revatio and Levitra) may report a sudden decrease or complete loss of vision.

Whether these events are directly related to these medicines or to other factors, have not been definitively proved.

However, if you experience sudden decrease or vision loss, it is strongly advised you discontinue taking online Viagra tablets or any PDE5 inhibitors you are using, and immediately contact your doctor.

Also, Viagra and other PDE 5 inhibitors have been implicated to cause sudden decrease or loss of hearing among people who use them.
Viagra tablets are the trademark of Pfizer, Inc., which are exclusively for the treatment of ED, and are not produced to treat any other form of sexual dysfunction.