It is very important that your doctor check your progress while you are receiving this medicine. This will allow your doctor to see if the medicine is working properly and to decide if you should continue to take it.
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.
Do not use this medicine if you are also using a nitrate medicine for chest pain (angina). Some examples of nitrate medicines are: isosorbide, nitroglycerin, Imdur®, Nitro-Bid®, Nitro-Dur®, Nitrol® ointment, Nitrolingual® spray, Nitrostat®, and Transderm Nitro®. Some illegal ("street") drugs or "poppers" also contain nitrates, such as amyl nitrate, butyl nitrate, or nitrite.
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.
Sildenafil injection could make your blood pressure go too low. Tell your doctor right away if you have more than one of these symptoms: blurred vision; confusion; dizziness, faintness, or lightheadedness when getting up suddenly from a lying or sitting position; sweating; or unusual tiredness or weakness.
If you experience a sudden loss of vision in one or both eyes, contact your doctor right away. This could be a symptom of a very serious eye condition called non-arteritic anterior ischemic optic neuropathy (NAION).
Check with your doctor right away if you have a sudden decrease in hearing or loss of hearing. You might also have dizziness and ringing in the ears.
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 tissue damage to the penis and possibly permanent impotence.