RESUMEN
BACKGROUND/AIMS: The marketing of newer agents for treatment of constipation and irritable bowel syndrome with constipation (IBS-C) emphasize improvements in abdominal pain. However, it is not clear whether this observation reflects a unique visceral analgesic effect of these agents or is a general feature of effective laxation. We sought to determine the relationship between improvements in bowel frequency and decreases in abdominal pain in clinical trials of patients with constipation or IBS-C. METHODS: We searched "PubMed" and "Embase" databanks for clinical trials in patients with constipation or IBS-C, targeting publications that provided detailed data on bowel movement frequency and pain intensity before and after an intervention. We abstracted the results and performed meta-analytic and meta-regression analyses. RESULTS: Twenty-seven trials (16 constipation and 11 IBS) met entry criteria. Baseline weekly bowel movement frequency was low with 2.35 (2.07-2.64) with differences between constipation (2.00 [1.62-2.38]) and IBS-C (2.77 [2.40-3.14]; Q = 8.18; P = 0.002). Studies reported moderate pain levels (2.12 [1.81-2.42]) with comparable baseline levels in constipation (2.02 [1.63-2.42]) and IBS-C (2.35 [2.10-2.60]; Q = 1.92; P = 0.167). Treatments increased bowel frequency by 2.17 [1.88-2.47] and lowered pain ratings by 0.58 [0.49-0.68]. Meta-regression demonstrated a significant correlation between treatment-induced increases in bowel frequency and decreased pain ratings. CONCLUSIONS: Our analysis suggests that reduction of abdominal pain observed in clinical trials of constipation and IBS-C is associated with laxation, and may not require specific drug mechanisms, thus arguing against a unique advantage of newer agents over traditional laxatives in the treatment of constipation and IBS-C.