Taking sildenafil as prescribed by your doctor is generally not harmful, and may be harmful when taken improperly without medical advice. Sildenafil is a type 5 phosphodiesterase inhibitor, a drug used to treat erectile dysfunction. When taken in accordance with medical advice, it is generally not harmful to the body, a small number of patients may have vomiting, headache and other adverse reactions, most of them are relatively mild, and generally do not have serious consequences. However, if it is applied in large quantities for a long period of time without following the doctor’s instructions, it may lead to certain hazards. In addition to the fact that the incidence of the above adverse reactions may be greatly increased, it may also cause serious adverse reactions such as shock, palpitations (rapid heartbeat, often accompanied by panic), tachycardia, and low blood pressure. The drug should always be applied strictly under medical supervision. It should also be noted that sildenafil prohibits the use of drugs in combination with nitrates, this drug is contraindicated in women, people who are allergic to the product, children, people whose recent cardiovascular state does not allow them to have sex.