Papaverine is a vasodilator that relaxes smooth muscles in your blood vessels to help them dilate (widen). This lowers blood pressure and allows blood to flow more easily through your veins and arteries. Papaverine is used to treat many conditions that cause spasm of smooth muscle. This includes chest pain, circulation problems, heart attack, or disorders of the stomach or gallbladder. Papaverine is not for use in treating erectile dysfunction (impotence) and should not be injected into the penis. This practice has resulted in painful or prolonged erection that may require surgery to correct. Papaverine may also be used for purposes not listed in this medication guide.