MONDAY, Jan. 17 (HealthDay News) -- Older people who are taking common blood pressure medications called calcium channel blockers face an increased risk of developing dangerously low blood pressure and possibly going into shock if they take certain antibiotics, Canadian researchers warn.
"Two common antibiotics, erythromycin and clarithromycin, if given to patients taking calcium channel blockers, can increase the risk substantially of being hospitalized for low blood pressure," said lead researcher Dr. David Juurlink, a scientist at Sunnybrook Research Institute in Toronto.
For patients taking erythromycin along with a calcium channel blocker the risk goes up almost sixfold, while it increases almost fourfold for patients taking clarithromycin, he said.
Although the interaction between these drugs has been known for some 20 years, this is the first time the risk has been quantified, Juurlink said.
Juurlink noted a cousin of these drugs, azithromycin, doesn't cause this problem. "One of the main suggestions of the study is, if you are on a calcium channel blocker and you need to go on an antibiotic in this class, azithromycin is a safer one to use," he said.
The report is published in the Jan. 17 edition of the Canadian Medical Association Journal.
For the study, Juurlink's team collected data on people aged 66 and older who were taking calcium channel blockers between 1994 and 2009.
The researchers sorted out who among these patients was hospitalized for low blood pressure (hypotension) and whether or not they had taken a macrolide antibiotic before being hospitalized.
Juurlink's group found that 7,100 of these patients had been hospitalized for low blood pressure or shock, and that having taken either erythromycin or clarithromycin was associated with an increased risk of trouble.
The reason these antibiotics have this effect is t
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