Trimethoprim and adverse outcomes in older patients

21 Mar 2018

Members of our group have recently published a paper investigating adverse effects of trimethoprim for the treatment of urinary tract infection.

We show that compared to other antibiotics used for the same reason, trimethoprim is associated with an increased risk of acute kidney injury  (a sudden reduction in kidney function) and high potassium levels but not an increased risk of death. Both of these adverse effects (acute kidney injury and high potassium) are known side-effects of trimethoprim but previous studies have only investigated the risks in people taking drugs that are already associated with an increased risk – for example, those that block the renin-angiotensin system, such as ACE Inhibitors. We examined the risk of these problems in the general population over 65 years of age and showed that the risk was increased for everyone. However, because these outcomes are rare for most people, the absolute risk of using trimethoprim is very low for most people. The paper attracted quite a lot of interest, particularly by people jumping to point out that the effect of trimethoprim on kidney blood tests might lead to a false diagnosis of acute kidney injury – something we explored in depth in the Discussion section of the paper. Laurie Tomlinson (the senior author of the paper) also wrote a linked blog post discussing the importance of electronic health records and how the evidence they generate can be used by researchers to make prescribing safer.


One of the key authors of this paper was our wonderful colleague Dr Adrian Root who sadly died earlier this year.  We miss him very much. We are planning to create an Electronic Health Records prize in his honour, and members of our group will be cycling to Paris later in the year to raise money for this – more details to follow!