Major antihypertensive drug classes: effects and precautions
THE CONTEXT
The passage describes thiazides, ACE inhibitors, angiotensin receptor blockers, calcium channel antagonists and beta-blockers used for hypertension.
Thiazides and loop diuretics
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The mechanism of thiazide action is incompletely understood, and the maximum effect may take up to a month.
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Appropriate daily doses stated are bendroflumethiazide 2.5 mg or cyclopenthiazide 0.5 mg.
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Loop diuretics such as furosemide 40 mg daily or bumetanide 1 mg daily offer few advantages over thiazides for hypertension unless substantial renal impairment is present or they are used with an ACE inhibitor.
ACE inhibitors and angiotensin receptor blockers
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ACE inhibitors are effective and usually well tolerated. Listed daily doses are enalapril 5–40 mg, ramipril 5–10 mg and lisinopril 10–40 mg.
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Use ACE inhibitors cautiously in impaired renal function or renal artery stenosis because they can reduce glomerular filtration rate and precipitate renal failure.
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Check electrolytes and creatinine before therapy and again 1–2 weeks after starting. Adverse effects include first-dose hypotension, cough, rash, hyperkalaemia and renal dysfunction.
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Angiotensin receptor blockers have similar efficacy to ACE inhibitors but do not cause cough and are better tolerated. Listed daily doses are irbesartan 75–300 mg and valsartan 40–160 mg.
Calcium channel antagonists
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Amlodipine 5–10 mg daily and nifedipine 30–90 mg daily are particularly useful in older people. Adverse effects include flushing, palpitations and fluid retention.
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Rate-limiting agents can be useful when hypertension coexists with angina, but may cause bradycardia. Listed doses are diltiazem 200–500 mg daily and verapamil 240–480 mg daily in divided doses.
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Constipation is the main adverse effect of verapamil.
Beta-blockers
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Beta-blockers are no longer first-line antihypertensive therapy unless another indication, such as angina, is present.
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Metoprolol, atenolol and bisoprolol preferentially block cardiac β1-adrenoceptors and are preferred over non-selective agents that also block β2-adrenoceptors, which mediate vasodilatation and bronchodilatation.
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Listed daily doses are metoprolol 100–200 mg, atenolol 50–100 mg and bisoprolol 5–10 mg.