atients treated with a combination of two types of hypertension drugs have an increased risk of cardiac death, kidney disease and likelihood of dialysis, the Heart and Stroke Foundation of Canada warns.

New guidelines have been released on the back of the announcement, which claims that combined treatment with ACE inhibitors and angiotensin II receptor blockers is not safe. As many as 175,000 Canadians with high blood pressure may be currently treated with this combination of drugs.

While safe and effective as single treatment options, the drugs were noted as dangerous when combined after the Foundation carried out a study that was published in the New England Journal of Medicine this year.

More than 25,000 patients took part in the trial, which showed that patients taking a combination of the drugs experienced more side effects, such as kidney problems, than those patients who only took one of the drugs. The drug combination of an ACE inhibitor and an ARB was also found to be only “marginally” more effective at lowering blood pressure than either of the drugs taken alone.

ACE inhibitors and ARBs both lower blood pressure through their action on the rennin-angiotensin system – a group of hormones regulated by the kidneys that control long-term blood pressure. However, the combined action of the drugs appears to put extra stress on the kidneys.

“This trial is a landmark study that helps healthcare providers better understand and more safely prescribe drug combinations for hypertension,” said Margaret Moy Lum-Lwong, director of the High Blood Pressure AIM Strategy of the Heart and Stroke Foundation of Ontario.

The Foundation also noted that when patients were removed from the combination they recovered from any side effects.