Viagra generally refers to sildenafil, which is not harmful to enlarged prostate. Sildenafil is a medication used to treat erectile dysfunction in men, this medication is not recommended for patients with cardiovascular disease, while it has no effect on patients with prostate enlargement. Sildenafil works by inhibiting the enzyme phosphodiesterase, which is broken down in the corpus cavernosum, to increase the release of nitric oxide, which stimulates the smooth muscles of the corpus cavernosum to relax, allowing blood to flow into the penis and allow an erection to occur; this process does not act on the prostate. Sildenafil is only effective when taken about an hour before sexual activity and accompanied by stimulation. Taking sildenafil may cause gastrointestinal reactions such as nausea, vomiting, abdominal pain, and diarrhea; cardiovascular adverse reactions such as chest tightness, chest pain, and dizziness may also occur. Patients with prostate enlargement are not recommended to take drugs such as chlorpheniramine maleate, promethazine hydrochloride, phenelzine, etc., which may aggravate prostate damage and can cause further urination difficulties. It is contraindicated for those who are allergic to this drug. Patients suffering from prostate hyperplasia are advised to undergo standardized treatment as soon as possible and take medication as prescribed by the doctor in order to reduce the adverse effects of the disease.