Calcium antagonist profiles, ivabradine and ranolazine
THE CONTEXT
Calcium channel antagonists used for angina have different dosing schedules and distinguishing effects. Ivabradine and ranolazine act through different ion-channel mechanisms.
Calcium channel antagonist doses and features
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Nifedipine is given at 5–20 mg three times daily and may cause marked tachycardia.
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Nicardipine is given at 20–40 mg three times daily and may cause less myocardial depression than the other calcium antagonists.
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Amlodipine is long-acting and is given at 2.5–10 mg daily.
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Verapamil is given at 40–80 mg three times daily. It commonly causes constipation and has useful anti-arrhythmic properties.
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Diltiazem is given at 60–120 mg three times daily and has anti-arrhythmic properties similar to verapamil.
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Once- or twice-daily sustained-release preparations are available for nifedipine, verapamil and diltiazem.
Ivabradine
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Ivabradine is described as the first drug in the I_f channel antagonist class, with an initial oral dose of 2.5–5 mg twice daily.
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It induces bradycardia by modulating ion channels in the sinus node.
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It does not inhibit myocardial contractility and appears safe in patients with heart failure.
Ranolazine
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Ranolazine is started at 375 mg twice daily.
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It inhibits the late inward sodium current in coronary artery smooth muscle cells.
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Secondary effects on calcium flux and vascular tone reduce angina symptoms.