Dr D Juurlink (University of Toronto) and colleagues recently reported their findings of their case-control study of patients aged 66 or older receiving ACE inhibitors or ARBs who died of sudden death within a week of receiving cotrimoxazole, amoxicillin, ciprofloxacin, norfloxacin or nitrofurantoin.

The risk of sudden death was more than a third higher with cotrimoxazole as compared to the other antibiotics. This risk was independent of other potential influencers of risk of sudden death.

The authors hypothesize that this may be due to the additive risk of hyperkalaemia due to both trimethoprim and the ACEI/ARB. Some patients will be particularly susceptible: patients with type 2 diabetes who are already pre-disposed to hyperkalaemia and patients with heart failure who may also be on other potassium-sparing medications such as spironolactone.