Viagra generally refers to sildenafil citrate, the drug onset time is related to the patient’s physique and other factors, the elderly take this product how long it takes to take effect is related to individual differences, usually in about half an hour. Sildenafil citrate is a PDE₅ inhibitor, mainly used in erectile dysfunction people, the drug onset of time is related to its absorption in the body, distribution and other factors, the normal onset of time in about half an hour after taking the drug. However, due to the different physical condition of each person, its specific onset of action time also varies. Some side effects may occur in the elderly after taking this product, such as gastrointestinal reactions, changes in vision, as well as nasal congestion and flushing. Also, some elderly patients with severe heart disease who take nitrates should not take it at the same time. The drug needs to be used under the guidance of a doctor, do not take it blindly on your own.