Clinical efficacies of antihypertensive drugs

According to published data, the ability to prevent various hypertension-related events differs between the various antihypertensive drug groups. Although absolute drug effects differ among studies, relative drug effects could be considered constant. We therefore explored the possibility of drawing statistically valid conclusions about the differences in clinical efficacy between various drug groups by doing an overview of published data.

We made a meta-analysis with a Bayesian fixed effect model in which we related the drug effects to the effects of placebo drugs. We selected 27 clinical trials from the literature according to specific criteria, including results from studies reporting the effects of the newer drugs when tested against diuretics and beta-blockers, and from studies in which diuretics and beta-blockers had been tested against placebo. We calculated the posterior probability distributions of the relative effects of angiotensin-converting enzyme (ACE) inhibitors vs calcium antagonists with three different endpoints: stroke, coronary disease and heart failure with point estimates of effects and with 95% credibility intervals. As an intermediate step in this procedure we obtained similar information about the effects of the three groups of active drugs, ACE inhibitors, calcium antagonists and diuretics or beta-blockers, tested against placebo. For coronary disease we also tested calcium antagonists against diuretics or beta-blockers.

ACE inhibitors and calcium antagonists have an almost identical ability to prevent stroke in hypertensive individuals with a risk ratio (RR) of 1.04. On the other hand, calcium antagonists reduce coronary disease by only 8% relative to placebo. When ACE inhibitors and calcium antagonists are compared with the Bayesian method, the outcome is a 14% difference in favor of the ACE inhibitors to prevent coronary disease, with a credibility interval almost reaching identity. Nor do calcium antagonists do as well as diuretics or beta-blockers in this respect, RR = 1.12 with 95% credibility interval 1.01-1.24. All the tested drug groups have a profound preventive effect on the occurrence of heart failure when given to hypertensive patients, showing reductions of 42-54%. When ACE inhibitors are compared with calcium antagonists RR = 0.79, with a credibility interval 0.65-0.95.

There is statistically an indisputable difference between ACE inhibitors and calcium antagonists in respect of effects on coronary disease and heart failure when treating hypertensive individuals, ACE inhibitors being more efficacious. There are no differences in the effect on stroke. Moreover, beta-blockers or diuretics are also superior to calcium antagonists in preventing coronary events.