Researchers at Georgia Tech have found the drugs known as ACE inhibitors are not as effective as other drugs and could actually be dangerous.

The study factors insurance claim data and electronic health records from 4.9 million patients across nine observational databases, making it the most comprehensive one ever on first-line anti-hypertensive drugs. It also provides additional context to the 2017 guidelines for high blood pressure treatment developed by the American College of Cardiology (ACC) and American Heart Association (AHA).

According to the report in the journal Lancet, thiazide diuretics demonstrate better effectiveness and cause fewer side effects than ACE inhibitors as first-line anti-hypertensive drugs.

First-Line Thiazide Diuretic Users Experience 15% fewer adverse cardiovascular outcomes than ACE inhibitor users, according to the findings. New users of first-line thiazide experienced three major medical outcomes (heart attack, hospitalization for heart failure, and stroke) at an approximately 15% lower event rate than those who began treatment with an ACE inhibitor. Furthermore, among potential side effects associated with first-line hypertensive drugs, ACE inhibitor new-users experienced a higher rate of 19 potential side effects — and a lower rate of two — than thiazide diuretic new-users.

In spite of these differences, the majority of patients from this study who initiated treatment were prescribed ACE inhibitors (48%) over thiazides (17%). The results, however, indicate that over 3,100 major cardiovascular events could potentially have been avoided had those approximately 2.4 million ACE inhibitor new-users chosen a thiazide diuretic instead.