Glyceryl Trinitrate

Question 1

GTN - mode of action

Answer 1

Ventilation - promotes venous pooling and reduces venous return therefore reduces preload.
Arteriodilation - reduces systemic vascular resistance and arterial pressure therefore reduces afterload.
Overall, reduces the heart workload and BP.

Question 2

GTN - indications

Answer 2

1. Chest pain in ACS
2. Hypertension in ACS
3. APO
4. Autonomic dysreflexia
5. Preterm labour

Question 3

GTN - contraindications

Answer 3

1. SYS BP <100
2. HR <50 (except in autonomic dysreflexia)
3. HR >150
4. VT
5. Riociguat current use
6. Bleeding in pregnancy
7. PDE5 inhibitors current/recent use

Question 4

GTN - precautions

Answer 4

1. Right ventricular MI or inferior STEMI with SYS <160 - use cautiously due to risk of severe hypotension
2. Preterm labour
3. Use lower doses for: elderly/frail, no previous exposure, or with recent MI

Question 5

GTN - side effects

Answer 5

1. Hypotension
2. Tachycardia
3. Bradycardia
4. Headache
5. Dizziness
6. Syncope
7. Skin flushing

Question 6

GTN - why is riociguat a contradiction

Answer 6

Riociguat (adempas) is used to treat pulmonary hypertension and GTN will increase hypotensive effects of adempas

Question 7

GTN - why are PDE5 inhibitors contraindicated

Answer 7

PDE5 inhibitors have hypotensive effects and GTN will increase these effects, resulting in profound hypotension.

Avanafil (spedra) - 12hrs
Sildenafil (viagra) or vardenafil (levitra) - 24hrs
Tadalafil (cialis) - 48hrs