THURSDAY, July 1 (HealthDay News) -- A new study warns that
seniors who take a common antibiotic combination for urinary tract
infections are at increased risk of developing potentially
life-threatening high potassium levels.
Researchers examined the medical records of 300,000 older adults
in the Canadian province of Ontario who were taking heart drugs
known as beta blockers. Of those, 189 patients had to be
hospitalized because their potassium levels reached dangerously
high levels after they took antibiotics to treat urinary tract
infections.
The patients who were most likely to develop the hazardous
potassium levels, known as hyperkalemia, took the widely prescribed
antibiotic TMP-SMX (a combination of
trimethoprim-sulfamethoxazole).
"Hyperkalemia is a potentially deadly adverse drug reaction," Dr. Matthew A. Weir, of London Health Science Center, said in a news release from the American Society of Nephrology. "TMP-SMX can decrease the kidney's ability to remove potassium from the body." Since potassium plays a key role in regulating heartbeat, he said, abnormally high levels of potassium "can cause fatal disturbances in the heart rhythm."
The risk of severe hyperkalemia was five times higher in
patients prescribed TMP-SMX compared to those prescribed
amoxicillin, another popular antibiotic to treat simple bladder
infections, Weir added.
Doctors may be able to help patients lower their risk by doing
blood testing to monitor their potassium levels, Weir said.
Since beta blockers and TMP-SMX can interact, the researchers
had speculated that patients taking both drugs would be at higher
risk of hyperkalemia. However, the increased risk of developing the
condition did not prove greater in patients who were also taking
beta blockers.
The study had several limitations, the researchers noted,
including the fact that data on predisposing factors wasn't
available and the patients were not assigned randomly to different
antibiotics. In addition, they wrote, the study might not apply to
younger patients.
The study was published online July 1 in the
Clinical Journal of the American Society of Nephrology.
More information
For more about urinary tract infections, see the
U.S. National Library of Medicine.