Usually, taking an occasional tablet of sildenafil will not affect your health. Sildenafil is a phosphodiesterase selective inhibitor, used for the treatment of penile erectile dysfunction. When taking sildenafil tablets orally, the concentration of the drug usually reaches its peak in about one hour, and most of them can be basically metabolized by the body completely in about six hours, so taking a piece of sildenafil occasionally won’t have a huge impact on the body. Long-term use of sildenafil will have some side effects, may appear dizziness, headache, weakness, abdominal pain, diarrhea and other symptoms, in addition to taking sildenafil during the period can not drink alcohol, taking nitroglycerin drugs are not recommended to take sildenafil, so as not to cause low blood pressure. It is recommended to take sildenafil under the guidance of a doctor.