The drugs, angiotensin-converting-enzyme or ACE inhibitors and angiotensin-receptor blockers, can raise potassium levels in about 10 percent of patients, especially those with weak kidneys, said Dr Biff Palmer of the University of Texas Southwestern Medical Center at Dallas.

"Because a third to half of patients with congestive heart failure have kidney complications, a large proportion of patients being treated with ACE inhibitors and angiotensin-receptor blockers are at increased risk for hyperkalemia (high potassium)," Palmer said in a statement.

Potassium is normally excreted by the kidneys, with levels in the blood affecting the way cell membranes work and governs the action of the heart and pathways between the brain and muscles.

High potassium levels can disrupt the heart's normal rhythm.

Doctors need to take note, Palmer advised.

"The patient's medication profile should be reviewed and drugs discontinued that impair excretion of potassium in the kidney, such as over-the-counter non-steroidal anti-inflammatory drugs like ibuprofen and naproxen," he said.

"Patients should be asked about the use of herbal remedies, as herbs can be a hidden source of potassium."

Patients at risk should avoid foods high in potassium such as orange juice, melons, bananas and salt substitutes.

Source: New England Journal of Medicine