Viagra generally refers to sildenafil, which cannot be taken regularly, and is prone to dizziness, indigestion and other adverse reactions when taken regularly. It is recommended to take it as prescribed by the doctor. Sildenafil can be used to treat erectile dysfunction, the drug’s common adverse reactions are mainly headache, flushing, dizziness, nasal congestion, indigestion, visual abnormalities. Rare adverse reactions mainly include facial edema, shock, weakness, pain, rash, tachycardia, palpitations, hypotension, and postural hypotension. Taking it regularly may lead to an increased incidence of the above mentioned adverse reactions, which is not good for your health. In addition, before taking this drug, you should also know its contraindications: for example, sildenafil is prohibited from combining with nitrate drugs, this drug is prohibited for women, people who are allergic to this product, children, and people who should not have sex in recent cardiovascular states. Sildenafil can not be eaten regularly, patients who need it can take it under the guidance of a professional doctor.