Ethosuximide not supported for IBS pain management

The T-type calcium channel blocker ethosuximide has shown limited benefit in the treatment of irritable bowel syndrome (IBS)-related abdominal pain in a proof-of-concept study.

The study included 124 adults (mean age 43.7 years, 58.1 percent women) meeting the Rome IV criteria for IBS (median duration 5 years), with abdominal pain intensity rated at least 4 out of 10 (mean 6) during a 7-day run-in period. These patients were randomly assigned to receive either ethosuximide (n=64) or placebo (n=60) for 12 weeks.

Responder rate, the primary endpoint, was defined as at least a 30-percent reduction in mean abdominal pain intensity along with a Subject Global Assessment relief score of at least 4 (ie, considerably or completely relieved). Secondary outcomes included safety, IBS symptom severity, and quality of life.

In the intent-to-treat analysis, the responder rate was 26.6 percent with ethosuximide vs 23.3 percent with placebo. The difference did not reach statistical significance (relative risk, 1.14, 95 percent confidence interval [CI], 0.61–2.11).

In terms of safety, ethosuximide was less well tolerated. More patients on ethosuximide vs placebo discontinued treatment (46.9 percent vs 21.7 percent; p=0.003). Of the 453 adverse events (AEs) reported, 261 were in the ethosuximide group and 202 were in the placebo group (56.4 percent vs 43.6 percent; p<0.001). The most common AEs were headaches, sleep disturbances, and nausea.