Viagra (sildenafil) is a medicine that can be prescribed if you experience repeated inability to have sex (also known as erectile dysfunction). This drug is most often prescribed to patients that are unable to have sex due to medical reasons, although those with psychological reasons may also take Viagra to regain confidence. Viagra is a serious medication with a number of contraindications and side effects that need to be taken into consideration. It's very important that you discuss your current health condition with your doctor just to make sure the treatment will bring you maximum benefits and you will be able to get fuller erections without experiencing any serious side effects. Viagra should be never combined with nitrate based drugs that can come in a variety of forms and are used to treat chest pain. Do not start taking Viagra if you are allergic to this medicine (its active ingredient – sildenafil citrate, or any of the inactive ingredients) or any other drugs and herbal preparations. If you take this drug in spite of your personal history of an allergic reaction, highly unpleasant and even dangerous symptoms of a severe allergic reaction are possible. Viagra should be taken by people with erectile dysfunction and is not intended for recreational purposes.