THE CONTEXT
Nitrate preparations differ in peak action and duration. Other anti-anginal vasodilators include calcium channel antagonists and the potassium channel activator nicorandil.
Peak action and duration of nitrates
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Sublingual glyceryl trinitrate (GTN) peaks at 4–8 minutes and acts for 10–30 minutes.
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Buccal GTN peaks at 4–10 minutes and acts for 30–300 minutes.
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Transdermal GTN peaks at 1–3 hours and acts for up to 24 hours.
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Oral isosorbide dinitrate peaks at 45–120 minutes and acts for 2–6 hours.
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Oral isosorbide mononitrate peaks at 45–120 minutes and acts for 6–10 hours.
Calcium channel antagonists
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Calcium channel antagonists lower myocardial oxygen demand by reducing blood pressure and myocardial contractility.
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Dihydropyridines such as nifedipine and amlodipine may cause reflex tachycardia and are best combined with a β-blocker.
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Verapamil and diltiazem can be used as monotherapy because they slow SA node firing, inhibit AV node conduction and tend to cause bradycardia.
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Verapamil and diltiazem are particularly useful when β-blockers are contraindicated.
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Use calcium channel antagonists carefully in patients with poor left ventricular function because their reduction of contractility can aggravate or precipitate heart failure.
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Other adverse effects include peripheral oedema, flushing, headache and dizziness.
Potassium channel activation
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Nicorandil is the only potassium channel activator described as available for clinical use in the source.
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The oral dose is 10–30 mg twice daily.
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Nicorandil dilates both arterial and venous systems and does not exhibit the tolerance seen with nitrates.