Viagra generally refers to sildenafil, and one capsule of sildenafil generally lasts for about 4 hours, depending on the individual’s constitution. Sildenafil is mainly a drug for treating erectile dysfunction in men, maintaining better erection hardness, and taking the drug can usually last for about 4 hours of efficacy. However, individuals have different physiques and absorb the drug differently, so when it comes to individuals, the length of time the drug lasts will also be different Flushing, nausea, headache and other symptoms may occur after taking sildenafil, the drug is forbidden to be combined with nitrate drugs, women, people who are allergic to the product, children, recent cardiovascular status should not have sex with the crowd prohibited this drug. The drug should be taken under the guidance of a doctor in accordance with the dosage, to avoid unauthorized use, causing damage to the body.