Methimazole treatment ups acute pancreatitis risk

Use of methimazole appears to elevate the risk of acute pancreatitis (AP), a recent study has found. This supports the warning issued by the European Medicine Agency (EMA) regarding a potential increased risk of AP in users of methimazole.

However, the risk increase may be limited to the first months of methimazole treatment. In absolute terms, the probability of AP is low among patients at <1 percent.

The investigators examined the association between methimazole and the diagnosis of AP in a population-based study by performing a retrospective analysis of administrative health databases (2013–2018). Pertinent data were obtained from inhabitants registry, hospital discharge records, and drug claims registry.

AP risk was assessed in methimazole users in 18 months of treatment, with results stratified by trimester. The investigators used Poisson regression to estimate the age- and sex-adjusted rate ratios (RR) and the relative 95 percent confidence intervals (CIs), comparing the rates of AP between users and nonusers. They also calculated the absolute risk of AP in methimazole users.

Overall, 23,087 new users of methimazole were identified, among whom 61 hospitalizations occurred during the study duration.

There was a significant increase in AP risk throughout therapy (first trimester: RR, 3.40, 95 percent CI, 2.12–5.48; second trimester: RR, 2.40, 95 percent CI, 1.36–4.23; third trimester: RR, 2.80, 95 percent CI, 1.66–4.73), but this risk increase disappeared later.

Of note, the absolute risk of AP in methimazole users during the first 18 months of treatment was <0.4 percent in all sex and age classes.