The side effects of taking sildenafil are relatively large, and if taken for a long time, it is easy to produce dependence on the drug. The more sildenafil the patient takes, the more obvious the headache will be; 4. Taking sildenafil may reduce male fertility, thus causing the possibility of infertility in the user; 5. If the patient is taking nitroglycerin or cardiac pain medication, it is not recommended that the patient take sildenafil again. Patients are advised to consult a doctor before taking sildenafil and use the drug with caution.