CARDIO: NITRATES

Question 1

NITRATES: INDICATIONS

Answer 1

• Acute Angina and ACS (short acting)
• Prophylaxis of Angina (long acting)
• IV nitrates = pulmonary oedema

Question 2

NITRATES: MOA

Answer 2

• Nitrates are converted to NO
• NO increases cAMP synthesis and reduces intracellular Ca2+ in vascular smooth muscle cells, causing them to relax
• This results in venous and, to a lesser extent, arterial vasodilatation.
• Relaxation of the venous capacitance vessels reduces cardiac preload and left ventricular filling. These effects reduce cardiac work and myocardial oxygen demand, relieving angina and cardiac failure.
• Nitrates can relieve coronary vasospasm and dilate collateral vessels, improving coronary perfusion. They also relax the systemic arteries, reducing peripheral resistance and afterload.

Question 3

NITRATES: ADVERSE EFFECTS

Answer 3

• Flushing
• Headaches
• Light headedness
• Hypotension
• Sustained use = tolerance and reduced symptom relief despite continuing use

Question 4

NITRATES: WARNINGS

Answer 4

• Nitrates are contraindicated in patients with severe aortic stenosis, in whom they may cause cardiovascular collapse.
• This is because the heart is unable to increase cardiac output sufficiently through the narrowed valve area to maintain pressure in the now dilated vasculature.
• Nitrates should also be avoided in patients with haemodynamic instability, particularly hypotension

Question 5

NITRATES: INTERACTIONS

Answer 5

• Must not be used with phosphodiesterase inhibitors

- Also use with caution in patients who are also on antihypertensive medication

Question 6

NITRATES: EXAMPLES

Answer 6

• isosorbide mononitrate

- glyceryl trinitrate