To provide you with the most relevant and helpful information, and understand which information is beneficial, we may combine your email and site usage information with other information we have about you. Who can and cannot take sildenafil Who can take sildenafil Most men aged 18 and over can take sildenafil for erectile dysfunction. Children 1 year of age and older weighing 20 kg or less—10 mg 3 times a day. Your doctor may adjust your dose as needed and tolerated. This medicine comes with a patient information leaflet. Leukemia blood related cancer or Multiple myeloma blood related cancer or Sickle-cell anemia blood disorder —Sildenafil should be used with caution in these patients as problems with prolonged erection of the penis may occur.In so doing, Viagra lowers the systolic blood pressure (the “top” number in blood pressure measurements) by an average of 8 mmHg. For most people with heart disease, including . Do not take sildenafil if you are also taking a nitrate drug (such as nitroglycerin or isosorbide dinitrate/mononitrate) for chest pain or heart problems. Do not take sildenafil . Medications. ED medicines can be pills, drugs inserted into the tip of the penis, or shots into the penis. The first things doctors usually prescribe to people with erectile dysfunction .