It is important that you tell all of your doctors that you take sildenafil. If you need emergency medical care for a heart problem, it is important that your doctor knows when you last took sildenafil.
Do not use this medicine if you are also using a nitrate medicine, often used to treat angina or high blood pressure. Nitrate medicines include nitroglycerin, isosorbide, Imdur®, Nitro-Bid®, Nitro-Dur®, Nitrol® ointment, Nitrolingual® spray, Nitrostat®, and Transderm Nitro®. Some illegal ("street") drugs called "poppers" (such as amyl nitrate, butyl nitrate, or nitrite). Do not use this medicine if you also use riociguat (Adempas®).
If you will be taking this medicine for pulmonary arterial hypertension, your doctor will want to check your progress at regular visits. This will allow your doctor to see if the medicine is working properly and to decide if you should continue to take it.
If you take sildenafil for pulmonary arterial hypertension, do not take Viagra® or other PDE5 inhibitors, such as tadalafil (Cialis®) or vardenafil (Levitra®). Viagra® also contains sildenafil. If you take too much sildenafil or take it together with these medicines, the chance for side effects will be higher.
Sildenafil should not be used with any other medicine or device that causes erections.
It is important to tell your doctor about any heart problems you have now or may have had in the past. This medicine can cause serious side effects in patients with heart problems.
If you experience a prolonged or painful erection for 4 hours or more, contact your doctor immediately. This condition may require prompt medical treatment to prevent serious and permanent damage to your penis.
If you experience a sudden loss of vision in one or both eyes, contact your doctor immediately.
Check with your doctor right away if you have a sudden decrease in hearing or loss of hearing, which may be accompanied by dizziness and ringing in the ears.
If you already use medicine for high blood pressure (hypertension), sildenafil could make your blood pressure go too low. Call your doctor right away if you have more than one of these symptoms: blurred vision, confusion, dizziness, faintness, or lightheadedness when getting up from a lying or sitting position suddenly, sweating, or unusual tiredness or weakness.
This medicine does not protect you against sexually transmitted diseases (including HIV or AIDS). Use protective measures and ask your doctor if you have any questions about this.
Do not take other medicines unless they have been discussed with your doctor. This includes prescription or nonprescription (over-the-counter [OTC]) medicines and herbal or vitamin supplements.