Sildenafil belongs to a group of medicines that delay the action of enzymes called phosphodiesterases that can interfere with erectile function. Sildenafil is used to treat men with erectile dysfunction (also called sexual impotence) because it helps to maintain an erection that is produced when the penis is stroked. Without physical stimulation of the penis, sildenafil will not work to cause an erection. Sildenafil is not indicated for use in women.
Sildenafil begins to work approximately 30 minutes after it is taken. The medication continues to work for up to four hours, although the effect is usually less after two hours.
Sildenafil is available by prescription and should be used only as directed by your physician. The dose of this medication will be different for different patients. Do not take more of this medication than has been prescribed for you.
Sildenafil can interact with, or interfere with, the action of other medications you may be taking. Be sure to inform your physician of all other medications you are taking so that appropriate substitutions or dosage adjustments can be made. Sildenafil should not be used by men who are using nitrates such as nitroglycerin (e.g., Nitrostat or Transderm-Nitro) to lower their blood pressure; sildenafil can cause the blood pressure to drop too far.
The presence of certain medical problems can interfere with the use of sildenafil. Be sure to inform your doctor if you have any of the following medical problems: an abnormality of the penis (including a curved penis or birth defect); bleeding problems; retinitis pigmentosa; any conditions causing thickened blood or slower blood flow (e.g., leukemia, multiple myeloma, polycythemia, sickle cell disease or thrombocythemia); a history of priapism (erection lasting longer than six hours); heart or blood disease; severe kidney problems; severe liver problems.
Sildenafil has not been studied in combination with other medications that are used in the treatment of erectile dysfunction. At the present time, it is not recommended that these drugs be used together.
Possible Side Effects
Side effects that you should report to your physician so that he or she can adjust the dosage or change the medication: flushing; headache; nasal congestion; stomach discomfort after meals; diarrhea.
Rare side effects that should be discussed with your physician: abnormal vision (e.g., blurred vision, seeing shades of colors differently than before, sensitivity to light); sudden decrease or loss of hearing; bladder pain; cloudy or bloody urine; dizziness; increased frequency of urination; painful urination.
Note: There are a variety of other possible side effects that have not yet been definitely shown to be caused by sildenafil. Therefore, if you notice any other effects that cause you concern, be sure to talk them over with your doctor.
* Since it may be difficult to distinguish between certain common symptoms of MS and some side effects of sildenafil, be sure to consult your health care professional if an abrupt change of this type occurs.