Medication Information Leaflet

What is this medication for?

Sildenafil is used to treat high blood pressure in the blood vessels in the lungs (pulmonary arterial hypertension). Sildenafil works by relaxing and widening the blood vessels in the lungs, and ultimately lowering the pressure in the lungs.

This should improve your symptoms such as breathlessness, and increase your ability to exercise. This medication has to be taken on a daily basis.

This medication may also be used for other conditions. Check with your healthcare professional if you are unsure why you are given this medication.

How should I take or use this medication?

• Do not stop taking your medication without checking with your healthcare professional as it may worsen your condition.
• This medication may be taken with or without food.
• This medication is usually started at a lower dose. Medication dosage will be adjusted based on your condition and your response to this medication will be monitored closely.

What should I do if I forget to take or use this medication?

• Take the missed dose as soon as you remember. Skip the dose if it is too near to your next dose. Then take your next dose at the usual time. Do not take two doses to make up for the missed dose.
• Do not take more than the dose prescribed to you.

What precautions should I take when taking or using this medication?

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. 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, speak to 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-blocker before you start drugs for pulmonary arterial hypertension (PAH)
• 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, a rare eye disease that affects the retina (the light sensitive layer of tissue in the back of the eye) where it changes how the retina responds to light slowly over time, ultimately causing loss of vision).
• 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.

Female patients of childbearing age should take precautions to avoid pregnancy by seeking advice from gynaecologist for effective contraceptive methods. If you suspect you may be pregnant, inform your cardiologist as soon as possible.

What are some common side effects of this medication?

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

What are some rare but serious side-effects that I need to seek medical advice immediately?

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

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.

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

What food or medication should I avoid when I take or use this medication?

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

Drinking alcohol 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 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.

How should I store this medication?

Store in a cool and dry place, away from direct sunlight. Keep this medication away from children. 

How do I throw away this medication safely?

Pack this medication into a black trash bag and seal it tightly before throwing into the rubbish chute or bin.

Disclaimer

Please take note that the above is not a complete list of all possible side effects. If you have any concerns about your medication or if you have other side effects that you think are caused by this medication, please consult your doctor or pharmacist.

If you take more than the recommended dose, please seek medical advice immediately. The information provided on this page does not replace information from your healthcare professional. Please consult your healthcare professional for more information.

This article is jointly developed by members of the National Medication Information workgroup. The workgroup consists of cluster partners (National Healthcare Group, National University Health System and SingHealth), community pharmacies (Guardian, Unity and Watsons) and Pharmaceutical Society of Singapore. The content does not reflect drug availability and supply information in pharmacies and healthcare institutions. You are advised to check with the respective institutions for such information.

Last updated on October 2022