It’s unclear which therapy is more effective because the evidence is insufficient. What is known is that tricyclic antidepressants, peppermint oil, and antispasmodics all have been shown superior to placebo for treating abdominal pain in female patients with irritable bowel syndrome (IBS) (strength of recommendation: A, meta-analyses).
Antispasmodics and tricyclics alleviate abdominal pain
A 2011 Cochrane review of 56 randomized controlled trials (RCTs) with 3725 patients compared bulking agents, antispasmodics, or antidepressants with placebo for treating IBS.1 The pooled results from 13 RCTs with 1392 patients (65% female, mean age 45 years) showed that more patients had improved abdominal pain with antispasmodics than placebo over treatment periods varying from 6 days to 6 months (58% vs 46%; relative risk [RR]=1.3; 95% confidence interval [CI], 1.1-1.6; number needed to treat [NNT]=7).
The clinical relevance of the antispasmodic data is limited because the antispasmodics found effective for abdominal pain aren’t available in the United States. The pooled results from 8 RCTs with 517 patients (72% female, mean age 40) demonstrated greater improvement of abdominal pain with tricyclic and selective serotonin reuptake inhibitor antidepressants than placebo over 6 to 12 weeks (54% vs 37%; RR=1.5; 95% CI, 1.1–2.1; NNT=5). However, subgroup analysis found a statistically significant benefit for tricyclic antidepressants (4 trials; N=320; RR=1.3; 95% CI, 1.0-1.6) but no benefit for SSRIs (4 trials; N=197; RR=2.3; 95% CI, 0.79-6.7).
Effective antispasmodics aren’t available in the United States
A 2012 meta-analysis of 23 RCTs with 2585 patients examined the effect of antispasmodic agents, alone or in combination, to treat IBS.2 Pooled results from 13 RCTs with 2394 patients (69% female, ages 16 years or older) favored treatment with antispasmodics over placebo for abdominal pain (odds ratio [OR]=1.5; 95% CI, 1.3-1.8). No difference in adverse events was found between antispasmodics and placebo (9 trials; N=2239; OR=0.74; 95% CI, 0.54-0.98). The antispasmodics found effective for abdominal pain in this meta-analysis aren’t available in the United States.