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High Blood Pressure

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Issue 6 Contents


Choosing additional therapy:
Calcium channel blocker or ACE inhibitor?

The priority is to achieve the reduction of blood pressure. The choice of a calcium channel blocker or ACE inhibitor, after the thiazide, is less important than reducing the blood pressure itself. Choice of agent is likely to depend on tolerability and concurrent medical conditions such as angina and heart failure and possible drug interactions. Achieving good compliance with a blood pressure lowering medicine is likely to be more important than the choice between ACE inhibitor or calcium channel blocker.

Calcium channel blocker interactions

Care is required with calcium channel blockers, particularly diltiazem, because of drug interactions. Diltiazem inhibits the elimination of medicines metabolised by cytochrome P450 3A4. This results in potentially significant increases in serum concentrations of some drugs e.g. simvastatin when diltiazem is added to therapy. Similarly diltiazem and other calcium channel blockers are susceptible to raised serum concentrations, when a macrolide antibiotic or azole antifungal is added to therapy, resulting in toxicity.

ACE inhibitor interactions

Care is required when an ACE inhibitor is used with a diuretic plus NSAID as renal function can deteriorate quickly. Of note 36% of the 33,357 people in ALLHAT had diabetes. Over the four years of the study there was no apparent additional benefit of ACE inhibitors over other blood pressure lowering medicines in people with uncomplicated diabetes (i.e. no microalbuminuria).

Drug-induced diabetes

Drug-induced diabetes differs to ‘natural’ diabetes associated with metabolic syndrome. We do not know the importance of an isolated increase in blood glucose concentration in the absence of metabolic syndrome. ACE inhibitors appear less likely to cause drug-induced diabetes. However, the clinical significance of drug-induced increased blood glucose is unclear, but the benefits of all blood pressure lowering medicines in cardiovascular outcomes appear to be greater in people with diabetes than without.

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