Viagra is an oral drug that is used for treating impotence (the inability to attain or maintain a penile erection). It is in a class of drugs called phosphodiesterase inhibitors that also includes sildenafil (Viagra) and vardenafil (Levitra).
For most individuals, the recommended starting dose of Viagra is 25 mg per day taken before sexual activity. Depending on the adequacy of the response or side effects, the dose may be increased to 50 mg or decreased to 25 mg a day. The effect of Viagra may last up to 5 hours.
How to use:
Individuals who are taking medications that increase the blood levels of Viagra should not exceed a total dose of 100 mg in 24 hours (See drug interactions). Viagra may be taken with or without food since food does not affect its absorption from the intestine.