Viagra (sildenafil citrate) is phosphodiesterase inhibitor specially designed for the needs of males that have erectile dysfunction and are unable to penetrate because of the insufficient erection. Your health care provider will need to be notified if you are taking any other drugs, as they can interact with Viagra and cause unpleasant reactions. Make sure you always discuss all the aspects of the treatment with a healthcare professional. The following medications should be used with caution and only after you have discussed that option with your doctor: cimetidine, erythromycin, rifamycins, alpha-blocker medications, high blood pressure medicines, HIV protease inhibitors, azole antifungals, other medications for impotence, or mibefradil. Any other ones you are using are also supposed to be reported - so make sure you let your doctor know about them before the treatment has started. Viagra is widely available online these days, and it is not a problem to get professional help there as well. At an online pharmacy you can get Viagra of the same high quality as anywhere - so it's worth taking a look at a few ones to choose some place safe and cheap.