Sildenafil should be administered at least 24 hours apart to ensure safe dosing.
The drug is a selective inhibitor of cyclic guanosine monophosphate (cGMP) specific type 5 phosphodiesterase (PDE5), and is one of the commonly used drugs in the treatment of erectile dysfunction. The drug is usually started about half an hour before intercourse, and the peak blood concentration is reached in about 1~2 hours. In order to ensure the safety of the drug, it is recommended that the patients use the drug for an interval of 24 hours.
In addition, because the drug may lead to a drop in blood pressure, patients need to use the drug under the guidance of a doctor. And, if patients have recently taken nitrate drugs, they must inform their doctors to prevent dangerous events.