GTN: Mode of Action
Organic nitrate – relaxes vascular smooth muscle
Venodilation promotes venous pooling and reduces venous return to the heart (reduces preload)
Arteriodilation reduces systemic vascular resistance and arterial pressure (reduces afterload)
Effects include:
Reduced myocardial O demand
Reduced systolic, diastolic and mean arterial blood pressure, whilst usually maintaining coronary perfusion pressure
Mild collateral coronary artery dilation may improve blood supply to ischaemic areas of myocardium
Mild tachycardia secondary to slight fall in BP
Preterm labour: uterine quiescence in pregnancy
GTN: Contraindications
BP < 100 mmHg
HR > 150
HR < 50 (except in autonomic dysreflexia)
Ventricular tachycardia
PDE5 inhibitors (current or recent use)(erectile dysfunction)
Riociguat (current use)(pulmonary hypertention)
Bleeding in pregnancy
GTN: Indications
Chest pain in acute coronary syndrome
Hypertension associated with acute coronary syndrome
Acute cardiogenic pulmonary oedema
Autonomic dysreflexia
Preterm labour
GTN: Precautions
Use lower doses (i.e. 300 mcg) in patients who are elderly (age > 60), have no previous exposure to GTN, or with recent MI, as they may be more susceptible to adverse effects.
Right ventricular MI or inferior STEMI with systolic BP < 160 mmHg - use cautiously due to risk of severe hypotension from preload reduction.
Preterm labour - concurrent use with other tocolytics.
Avoid skin contact with concentrated solution.
GTN: Presentation/Route of administration
Presentation:
0.3 mg tablet (Nitrostat)
50 mg patch (releases 0.4 mg / hr or 10 mg / 24 hours)
Route:
Sublingual
Transdermal patch
GTN: Adverse effects
CV: hypotension, tachycardia, bradycardia (occasionally)
Other: skin flushing
