Eight RCTs (n=4,170) were included in the review.
Two studies had a quality score of 5 points, four had a quality score of 4 points, and two had a quality score of 3 points.
Global improvement in irritable bowel syndrome symptoms: There was a significant global improvement in irritable bowel syndrome symptoms with treatment compared to placebo (RR 1.60, 95% CI 1.44 to 1.76; three trials); there was no significant statistical heterogeneity between the studies.
Adequate relief of irritable bowel syndrome pain and discomfort: There was a significant difference in favour of alosetron compared to placebo (RR 1.31, 95% CI 1.20 to 1.43; six trials). There was no significant statistical heterogeneity between the trials. Results were similar when males and females were analysed separately.
Adverse events: Significantly more adverse events were reported in participants who received alosetron compared to placebo (RR 1.19, 95% CI 1.07 to 1.31; seven trials); there was significant statistical heterogeneity between the trials. When compared to placebo, there was significantly greater constipation (RR 4.35, 95% CI 3.01 to 6.26; eight trials) and abdominal pain and discomfort (RR 1.96, 95% CI 1.46 to 2.64; five trials) in participants who received alosetron. There were no significant differences between groups for nausea, ear, nose and throat infections, or headache. Ischaemic colitis (0.16%) and serious complications of constipation (0.08%) were reported in a small number of participants treated with alosetron.