Sildenafil (for erectile dysfunction)

Common side effects include:​

• Facial flushing where the skin on your face feels hot
• Headache
• Visual disturbances (including blurring of vision, blue tinge in vision)
• Indigestion or stomach pain
• Nosebleed

Rare but serious side effects include:

• Priapism (an erection that will not go away) - If you have an erection that lasts more than 4 hours, get medical help right away. If it is not treated right away, priapism can permanently damage your penis.
• Sudden vision loss in one or both eyes - Sudden vision loss in one or both eyes can be a sign of a serious eye problem called non-arteritic anterior ischemic optic neuropathy (NAION).
• Sudden hearing decrease or hearing loss - Some people may also have ringing in their ears (tinnitus) or dizziness.

The symptoms of a drug allergy include one or more of the following:

• Swollen face/eyes/lips/tongue
• Difficulty in breathing
• Itchy skin rashes over your whole body

If you experience any of these symptoms, you should stop your medication and see your healthcare professional immediately.

​Inform your healthcare professional if:

• You are allergic to this medication or any of the other ingredients of this medication
• You are taking medicines called Nitrates (such as sublingual nitroglycerin (also known as Glycerin Trinitrate or GTN), Isosorbide Mononitrate or Isosorbide Dinitrate), as the combination may lead to a dangerous fall in your blood pressure. Nitrates must be withheld at least 24 hours after the last dose of Sildenafil or Vardenafil, and 48 hours after the last dose of Tadalafil. Tell your doctor if you are taking any of these medicines which are often given for relief of angina (chest pain).  If you are not certain, ask your healthcare professional
• You are taking medicines called Alpha-1 Blockers (such as Tamsulosin, Terazosin, Prazosin, Alfuzosin), as the combination may further lower your blood pressure. In order to reduce the chances of these symptoms occurring, you should be on a regular daily dose of your Alpha-1 blockers before you start drugs for erectile dysfunction
• You recently had a stroke or a heart attack, low blood pressure or uncontrolled high blood pressure
• You have severe heart, liver or kidney  problem
• You have certain rare inherited eye diseases (such as retinitis pigmentosa)
• You have a stomach ulcer or bleeding problem
• You have sickle cell anaemia (an abnormality of red blood cells)
• You have a deformity of your penis

Avoid taking grapefruit, or grapefruit juice as they may interact with your medication and increase the risk of side-effects.

Drinking alcohol can temporarily weaken your ability to get an erection and may increase the blood pressure lowering effects of the medication, which can be dangerous. To get the maximum benefit from your medication, it is advisable not to drink excessive amounts of alcohol before taking this medication.

Inform your healthcare professional if you are taking or intend to take any other medication, supplements, traditional medications or herbal remedies.

This includes certain medications such as:

• Antibiotics
• Anti-fungal medications
• Medications used to treat human immunodeficiency virus (HIV) infection