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High Blood Pressure

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Issue 6 Contents
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where are we at?

The recent literature has raised doubts about the role of ß-blockers for lowering blood pressure and the New Zealand Guidelines Group is updating the Assessment and Management of Cardiovascular Risk Guideline.

As we await the new guideline, general practitioners have asked us for some guidance for their day-to-day decisions on blood pressure management.

Key Advisor; Dr Linda Bryant, Clinical Advisory Pharmacist
Reviewed by Professor Rod Jackson, University of Auckland

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What is the role of β-blockers in the treatment of hypertension?

  • ß-blockers are appropriate first-line blood pressure lowering medicine when there is a concurrent medical condition for which ß-blockers have been proven effective, such as angina, previous myocardial infarction, heart failure or atrial fibrillation.
  • In younger people ß-blockers are unlikely to have a significant benefit over other antihypertensive medicines. A thiazide is the preferred first-line medicine in all people.
  • In older people a thiazide is the preferred first-line antihypertensive and ß-blockers are only used if there is a concurrent medical condition requiring a ß-blocker, or as adjunctive therapy to achieve good blood pressure control after an ACE inhibitor or calcium channel blocker.
  • Start with the lowest dosage of ß-blocker for high blood pressure and increase every four weeks if required.

When a β-blocker is indicated, which one should we use?

  • Metoprolol has proven benefits of improved morbidity and mortality from myocardial infarction and heart failure in people with hypertension.
  • While ß-blockers in general, are looking less desirable as first-line blood pressure lowering medicines in uncomplicated hypertension, atenolol is potentially the least effective.

If β-blockers are not indicated, which antihypertensive is first choice?

  • Thiazides are still the mainstay of blood pressure lowering therapy and should be used as first-line medicines unless there is a good reason not too. Adverse effects are generally not clinically significant, including the effects on blood glucose and serum cholesterol.
  • At the time of deciding to treat high blood pressure, the use of aspirin and a statin should also be considered as a multi-faceted intervention to reduce the cardiovascular risk.

Choosing additional therapy: Calcium channel blocker or ACE inhibitor?

  • The choice of medication to add to a thiazide depends on the other medical conditions of the person.
  • When a ß-blocker is not indicated for concurrent conditions either an ACE inhibitor or calcium channel blocker is appropriate, especially in older people.
  • It appears that a thiazide plus ACE inhibitor has a synergistic effect and is a suitable combination.

Medications for blood pressure management
Summary table

A combination of two or three classes is often required

Medication Benefits Risks Suggestions
Thiazide More effective than Ca channel blocker or ACE inhibitor in protecting against heart failure,
as effective for other clinical endpoints.
More metabolic changes, but seldom clinically significant.
Usual first-line therapy in all age groups
ACE inhibitors Synergistic with thiazides.
As effective as Ca channel
blockers.
Reduces progression of renal
failure.
Effective in heart failure.
Acute renal failure when used with diuretic plus NSAID (Triple Whammy).
Less effective in people of African or Caribbean descent.
Second-line therapy
Ca Channel blockers As effective as ACE inhibitors.
Benefits in angina
Drug interactions.
May have unfavourable effects on heart failure.
Risks with heart block.
Alternative second-line therapy
ß-blocker Proven effectiveness in management of angina, post MI, heart failure, AF.
Migraine prophylaxis.
Appear less effective at reducing cardiovascular risk in older people.
Atenolol appears least effective.
May aggravate peripheral vascular disease.
Risks with asthma.
Risks with heart block.
Hold in reserve unless another reason for using them
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