glyceryl trinitrate: clinical use

Prescribing considerations

• Confirm the formulation and indication; patches prevent angina but do not rapidly relieve an acute attack.
• Assess volume status, blood pressure, cardiovascular obstruction and concurrent vasodilators.
• Continuous exposure can produce nitrate tolerance.
• Intravenous use requires hospital-level cardiovascular and haemodynamic supervision.
• Rectogesic is licensed for chronic fissure pain rather than healing, and severe headache commonly limits treatment.

Contraindications and cautions

• PDE5 inhibitors; riociguat where specified; and contraindicated concurrent nitrate or nitric-oxide-donor therapy.
• Shock, severe hypotension or severe hypovolaemia.
• Severe anaemia or hypersensitivity to organic nitrates.
• Raised intracranial pressure and selected obstructive cardiac conditions.
• Rectogesic-specific contraindications include migraine or recurrent headache and closed-angle glaucoma.

Monitoring

• Blood pressure, pulse, symptoms and orthostatic effects.
• Continuous cardiac and circulatory monitoring during intravenous treatment.
• Coagulation response with intravenous heparin.
• Consider methaemoglobinaemia with unexplained cyanosis or hypoxaemia.
• Patch or rectal-ointment application sites.

Clinical pharmacology

GTN is converted to nitric oxide, activating soluble guanylate cyclase and increasing cyclic GMP. Predominant venodilation reduces preload and myocardial oxygen demand; arterial dilation reduces afterload. Transdermal systems provide sustained systemic delivery.

Formulation and product differences

• Under-the-tongue formulations provide rapid systemic absorption for angina symptoms.
• Patches provide sustained preventive delivery and may maintain peripheral venous patency.
• Rectal ointment acts locally on the internal anal sphincter but can cause systemic nitrate effects.
• Infusion is reserved for closely monitored acute cardiovascular or perioperative settings. PVC administration sets should be avoided for the Macure product because GTN adsorbs to PVC.

Solution for infusion

Route: Intravenous

Strengths: 1 mg/mL

Rectal ointment

Route: Rectal

Strengths: 4 mg/g

Transdermal patch

Route: Transdermal

Strengths: 5 mg/24 hours, 10 mg/24 hours