Caution should be used when administering GTN to what type of patients?

Answer 1

I would sat caution should be exercised when prescribing to ALL patients. Its a drug which can have nasty side effects and needs to be monitored. It can cause a severe allergic reaction;

Answer 2

Glyceryl trinitrate - GTN - works by releasing a chemical called nitric oxide. This chemical is also made naturally by the body and has the effect of making the veins and arteries relax and widen (dilate). This increases the space within the blood vessels and therefore reduces the resistance within the blood vessels, which makes it easier for the heart to pump blood around the body.
Widening the veins also decreases the volume of blood that returns to the heart in the veins with each heartbeat, and this makes it easier for the heart to pump that blood out again. As a result of both these actions, the heart requires less energy to pump the blood around the body and therefore does not need as much oxygen. The medicine also widens the arteries within the heart, and this increases the blood and oxygen supply to the heart muscle. The pain of angina is caused by too little oxygen reaching the heart when its workload increases, such as during exercise. Glyceryl trinitrate makes it easier for the heart to pump blood and so decreases the amount of oxygen that the heart needs, as well as improving the oxygen supply to the heart. It can therefore be used to relieve the pain of an angina attack. Short-acting glyceryl trinitrate tablets should be kept in the container they are dispensed in and discarded after eight weeks. The tablets may lose their effectiveness if the container has been open for longer than eight weeks or if they are transferred to a different container. This medicine may cause dizziness and so may affect your ability to drive or operate machinery safely. Do not drive or operate machinery until you know how this medicine affects you and you are sure it won't affect your performance. This medicine is not recommended for use in children. Follow the instructions you receive with this medicine. Glyceryl trinitrate sublingual tablets should be allowed to dissolve under the tongue - they should not be swallowed like normal tablets. Glyceryl trinitrate spray should be sprayed under the tongue, and the mouth closed after each dose. Do not inhale the spray. Drinking alcohol may enhance some of the side effects of this medicine, such as feeling faint or dizzy. Do to use it if – There is Allergy to nitrates, Bleeding in the brain (cerebral haemorrhage), Blood in the sac surrounding the heart which prevents the heart beating properly (cardiac tamponade), Closed angle glaucoma, Head injury, Heart disease in which the muscle of the heart grows abnormally (hypertrophic obstructive cardiomyopathy), Inflammation of the sac surrounding the heart which stops the heart from beating properly (constrictive pericarditis), Low blood pressure (hypotension), Low volume of circulating blood (hypovolaemia).
Hope this helps.
Matador 89

Answer 3

Two main things:

1) the patient has already taken the maximum allowed dose of GTN

Also, since GTN dilated the blood vessels, thereby decreasing blood pressure:

2) hypotension. If the patient's systolic blood pressure is under 90mmHg, abnormally slow/fast hear trate (<50 or >100bpm).

Hope this helps.

Answer 4

http://www.cs.nsw.gov.au/rpa/neonatal/html/meds/gtn.htm