July 28 (UPI) -- Some drugs prescribed to people with high blood pressure and congestive heart failure weaken the immune system's ability to fight off bacterial infections, a study published Wednesday by Science Translational Medicine found.
As a result, angiotensin converting enzyme, or ACE inhibitors, may leave some users more vulnerable to potentially life-threatening infections such as methicillin-resistant Staphylococcus aureus, or staph, the researchers said.
"Angiotensin-converting enzyme inhibitors are used by millions of patients to treat hypertension, diabetic kidney disease and heart failure," researchers from Cedars-Sinai Medical Center in Los Angeles wrote.
"[Our results] demonstrate that ACE inhibitor treatment can reduce the bacterial killing ability of neutrophils," which are immune cells that help fight bacterial infections, they said.
ACE inhibitors are designed to relax arteries, veins and capillaries to lower blood pressure, according to the American Heart Association.
Earlier research has suggested that ACE supports neutrophils, which are produced by the immune system to help the body fight bacterial infections.
For this study, Khan and his colleagues tested in mice the commonly used ACE inhibitors ramipril, which is sold under the brand name Altace, and lisinopril, which is sold under the brand Zestril, among others.
The drugs weakened neutrophils' ability to kill staph bacteria in infected mice, leading to more severe infections, the researchers said.
A different type of blood pressure drug -- the angiotensin receptor blocker losartan, which is sold under the brand name Cozaar -- did not substantially impact antibacterial immunity in mice.
In a separate experiment, the researchers collected sample neutrophils from seven human volunteers given ramipril at the standard dose for one week.
Those treated with the drug had neutrophils that were unable to produce key molecules involved in antibacterial immune responses, they said.
The sample neutrophils collected from these patients also killed fewer bacteria in lab experiments, which suggests that ACE inhibitors may also suppress neutrophils in humans, according to the researchers.
People on ACE inhibitors "are often at increased risk of infection," the researchers wrote.
Physicians may want to consider this issue when deciding whether to prescribe ACE inhibitors or angiotensin receptor blockers, they said.