Prescribing antibiotics to older patients receiving spironolactone is associated with a major increase in the risk of admission to hospital for hyperkalaemia, a BMJ study shows.
A case-control study of a population on elderly patients aged 66 or older in Ontario, Canada, shows those receiving chronic treatment with spironolactone had a 12-fold-increased risk of being admitted to hospital with hyperkalaemia within 14 days of a prescription.
During the 18-year study period, 6,900 admissions for hyperkalaemia were identified, 306 of which occurred within 14 days of a prescription of co-trimoxazole, amoxicillin, norfloxacin or nitrofuranoin. After matching cases to controls 10.8% of spironolactone users received at least one prescription for trimethoprim-sulfamethoxazole.
Compared with amoxicillin, prescription of co-trimoxazolewas associated with a ‘marked’ increase in the risk of admission to hospital for hyperkalaemia, with an adjusted odds ratio of 12.4.
Dr David Juurlink, clinical epidemiologist at the Sunnybrook Research Institute in Toronto, concluded: ‘This drug combination should be avoided when possible.’
BMJ 2011, online 12 September