Ondansetron for Low Anterior Resection Syndrome (LARS): A Double-Blind, Placebo-Controlled, Cross-Over, Randomized...

The aim of the study was to examine the efficacity and safety of ondansetron, a serotonin receptor antagonist, to treat patients with low anterior resection syndrome (LARS).

LARS after rectal resection is common and debilitating. Current management strategies include behavioral and dietary modifications, physiotherapy, antidiarrheal drugs, enemas, and neuromodulation, but the results are not always satisfactory.

This is a randomized, multicentric, double-blinded, placebo-controlled, and cross-over study. Patients with LARS (LARS score >20) no longer than 2 years after rectal resection were randomized to receive either 4 weeks of ondansetron followed by 4 weeks of placebo (O-P group) or 4 weeks of placebo followed by 4 weeks of ondansetron (P-O group). The primary endpoint was LARS severity measured using the LARS score; secondary endpoints were incontinence (Vaizey score) and irritable bowel syndrome quality of life (IBS-QoL questionnaire). Patients' scores and questionnaires were completed at baseline and after each 4-week treatment period.

Of 46 randomized patients, 38 were included in the analysis. From baseline to the end of the first period, in the O-P group, the mean (SD) LARS score decreased by 25% [from 36.6 (5.6) to 27.3 (11.5)] and the proportion of patients with major LARS (score >30) went from 15/17 (88%) to 7/17 (41%), ( P =0.001). In the P-O group, the mean (SD) LARS score decreased by 12% [from 37 (4.8) to 32.6 (9.1)], and the proportion of major LARS went from 19/21 (90%) to 16/21 (76%). After crossover, LARS scores deteriorated again in the O-P group receiving placebo, but further improved in the P-O group receiving ondansetron. Mean Vaizey scores and IBS QoL scores followed a similar pattern.

Ondansetron is a safe and simple treatment that appears to improve both symptoms and QoL in LARS patients.