Glyceryl Trinitrate - Rectal

Patient Medicine Information
Why do I need this medicine?
Glyceryl Trinitrate (GTN) rectal ointment belongs to a group of medicines known as nitrates and is used to relieve the pain caused by chronic (long-term) anal fissures. Anal fissures are tears or breaks in the skin lining of the anal canal. This medicine helps to reduce the anal pressure and increase the blood flow thereby reducing pain.
How do I use this medicine?
Apply GTN ointment exactly as directed by your doctor or according to the instructions on the label. DO NOT apply larger amounts or more frequently than instructed by your doctor.
  1. Wash your hands thoroughly.
  2. Place your finger alongside the dosing line printed on the outside carton of the ointment tube.
  3. Squeeze the tube to release a length of ointment onto your finger corresponding to the 2.5 cm line indicated on the carton.
  4. Gently insert your finger into the anal canal. Apply the ointment around the area in a gentle, circular motion. The finger must be inserted up to the first finger joint (about 1 cm) into the anus.
  5. Wash your hands after applying the ointment. You may use a finger cot to apply the ointment instead of your bare finger.
The dose of this medicine will be decided by your doctor. Your doctor will advise you on the treatment timeframe depending on the severity of your condition.
What should I do if I have forgotten to use this medicine?
Apply the missed dose as soon as you remember. If it is almost time for your next dose, skip the missed dose and return to your normal dosing schedule.

DO NOT double a dose under any circumstances.

If you often forget to apply your medicine, let your doctor and pharmacist know.
When should I not use this medicine?
Alert your doctor if you have the following conditions:
  • history of heart problems e.g. pericarditis (inflammation of the heart), valve stenosis (narrowing of the heart valves)
  • increased pressure in the skull due to bleeding in the brain or head injury
  • migraine and recurrent headache
  • low blood pressure
  • severe anaemia (low red blood cell counts)
  • glaucoma (increased eye pressure)
as GTN may not be suitable for you.

Do not give this medicine to children below 18 years old unless instructed to do so by the doctor.

Do not use GTN with medicines used to treat impotence, chest pain and medicines used to manage high blood pressure in the arteries of the lungs. Please see the section “Can I take this with other medicines?” below for more information.
What should I take note of while using this medicine?
Inform your doctor if you have the following:
  • liver disease
  • kidney disease
  • haemorrhoids (piles) which seem to bleed more than usual
Let your doctor know if you are pregnant or breastfeeding.

Be sure to check with your doctor or pharmacist before giving this medicine to an elderly. Elderly people may be more sensitive to the side effects.
What side effects could I experience?
GTN may cause dizziness, blurred vision, headache or tiredness, especially on first use. If affected, do not drive or take part in any activity in which you need to be alert or need to see clearly.

This medicine may cause your blood pressure to fall suddenly when you get up from a sitting or lying down position and you may feel giddy. To minimise this problem, stand up slowly.

Other side effects include any of the following: nausea, diarrhoea, vomiting, itching or burning of the anal canal and rapid heartbeat.

Inform your doctor if any of these side effects do not go away or are severe, or if you experience other side effects.
Can I use this with other medicines?
Do not use GTN with the following medicines:
  • medicines used to treat impotence e.g. sildenafil, tadalafil, vardenafil
  • medicines for chest pain e.g. isosorbide dinitrate
  • riociguat (medicines used to manage high blood pressure in the arteries of the lungs)
Inform your doctor and pharmacist if you are taking any of these medicines:
  • medicines for high blood pressure e.g. enalapril, atenolol
  • medicines to treat depression e.g. amitriptyline
  • dihydroergotamine (medicine for migraine)
  • acetylcysteine (medicine for cough with phlegm)
  • blood-thinning medicines e.g. heparin, alteplase
  • NSAIDs (medicine for pain and inflammation) e.g. aspirin
This list does not include all medicines that may interact with GTN.

Always notify your doctor and pharmacist if you are taking any other medicines, including herbal tonics, such as traditional Chinese medicine, supplements and medicines that you buy without a prescription.
What special dietary instructions should I follow?
Avoid alcohol.
How should I store this medicine?
Store in a cool, dry place away from the reach of children.

Medicines must not be used past the expiry date.

Discard 8 weeks after opening.
This information is independently developed by MIMS based on Glyceryl Trinitrate - Rectal and is provided for your reference only. It is not a replacement for and should only be used in conjunction with full consultation with a licensed healthcare professional, the information provided by your pharmacist and/or the manufacturer of the medication. It may not contain all the available information you require and cannot substitute professional medical care, nor does it take into account all individual circumstances. Although great effort has been made to ensure content accuracy, we shall not be held responsible or liable for any claims or damages arising from the use or misuse of the information contained herein, its contents or omissions, or otherwise. Copyright © 2021 MIMS. All rights reserved. Powered by
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