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Dr Diana R Holdright
MD, FRCP, FESC, FACC, MBBS, DA, BSc

Consultant Cardiologist

Dr Diana Holdright
 
 

Drug Therapy - Hypertension

The latest British Hypertension Society guidelines* define normal blood pressure as <130/<85 mmHg. Optimal blood pressure level is now classified as <120/<80 mmHg, and people with high-normal blood pressures (130-139/85-89 mmHg) should be reassessed on an annual basis. Drug treatment should be considered for individuals with blood pressures of 140/90 mmHg or higher; for people on antihypertensive therapy targets are <140/<85 mmHg (<130/<85 mmHg in people with diabetes). Use of a home blood pressure monitor gives invaluable information on the effectiveness of treatment, rather than relying on infrequent “one-off” readings with a doctor. Readings made at home are often 5 to 10 mmHg lower than at the surgery, and indeed some patients find that their blood pressure readings are significantly higher with a doctor than usual, a condition known as “white coat hypertension”. 

In addition to lifestyle changes such as losing weight, taking regular exercise and cutting down on salt and alcohol intake, there are a number of different drug classes which can lower blood pressure. Most patients need more than one drug to lower blood pressure adequately and treatment is usually for life. The first drugs for lowering blood pressure became available in the 1950s; since then a number of new classes of drug have been developed and shown in large clinical trials to lower the risk of stroke and heart disease, the magnitude of benefit being commensurate with the extent of blood pressure lowering. Patients respond differently and often unpredictably to antihypertensive drugs; one drug class may have no effect on a patient’s blood pressure, whereas a different drug class may lower the blood pressure significantly. Age and racial origin are important determinants of response to therapy; for example, blood pressure lowering in patients over 55 years and in patients of black ethnic origin at any age will usually be greatest with the thiazide-type diuretics and calcium channel blockers, two classes of antihypertensive.  Other classes of drug include ACE inhibitors and angiotensin receptor blockers (ARBs); beta blockers are less frequently used these days.  For more refractory cases alpha receptor blockers, spironolactone and centrally acting drugs may be prescribed. The latest addition to the armamentarium is aliskiren, which is a new class of drug altogether, a direct renin inhibitor.

Each drug class has a specific mechanism of action; many drugs have additional beneficial effects beyond blood pressure lowering, such that the choice of drug will, in part, be influenced by any other co-existing conditions. For example, a patient who has high blood pressure and has also suffered a previous heart attack would benefit from ACE inhibitors, ARBs and beta blockers, which all have additional protective effects; a patient with angina would benefit from beta blockers and calcium channel blockers; ACE inhibitors, ARBs, beta blockers and spironolactone would be beneficial in a patient with heart failure; and diabetics and patients with kidney disease would derive additional benefit from ACE inhibitors and ARBs.  

An important point of note is that once an effective regime has been established to lower blood pressure it should be continued; if the drugs are stopped the blood pressure will immediately rise to pre-treatment levels or higher, since these drugs work by suppressing high blood pressure, not curing it.

* Bryan Williams, Neil R Poulter, Morris J Brown, Mark Davis, Gordon T McInnes, John F Potter, Peter S Sever, Simon McG Thom; the BHS guidelines working party, for the British Hypertension Society. Guidelines for hypertension management 2004 (BHS-IV): Summary

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Drug Therapy - HypertensionDrug Therapy - Hypertension