Choosing antihypertensives, combining drugs and assessing resistance
THE CONTEXT
Drug selection depends on patient characteristics and comorbidities, while inadequate control may require combination therapy and assessment of adherence or secondary causes.
Initial drug selection
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Comparative trials of thiazides, calcium antagonists, ACE inhibitors and angiotensin receptor blockers have not shown consistent differences in outcomes, efficacy, adverse effects or quality of life. Beta-blockers have a weaker evidence base.
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Age and ethnic background initially dictate treatment choice. Cost and convenience influence the exact drug and preparation; response and adverse effects guide subsequent treatment.
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Comorbidities influence selection: a beta-blocker may be appropriate for a patient with angina.
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Thiazide diuretics and dihydropyridine calcium channel antagonists are the most suitable drugs for older people.
Combination therapy
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Multiple drugs are often needed for optimal blood pressure control.
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Low doses of two drugs may cause fewer unwanted effects than the maximum dose of one drug.
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Some combinations have complementary or synergistic actions. Thiazides increase renin–angiotensin system activity, whereas ACE inhibitors block it.
Resistant hypertension
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Resistant hypertension means inadequate blood pressure control despite multiple drug treatments.
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Non-adherence is a more common cause of treatment failure than genuine resistance. Unrecognised renal artery stenosis or phaeochromocytoma can also cause resistant hypertension.
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Simple regimens, improved rapport and careful supervision can help address adherence problems.
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Spironolactone is a particularly useful additional drug in treatment-resistant hypertension.