OBJECTIVES: To assess treatment patterns and associated health care cost in mebeverine users relative to matched controls. METHODS: A matched case-control study was performed using pharmacy data. Cases were mebeverine users as proxy for IBS patients. Controls were non-mebeverine users and matched to cases by age, gender and pharmacy. Prevalence and incidence of mebeverine use were estimated and concomitant drug use and hospitalisations were assessed in 3431 cases and 3431 controls. Concomitant drug use and hospitalisations was also assessed in a subgroup of 1222 users of mebeverine and laxatives (proxy for constipation-IBS) and their controls. RESULTS: Twelve per 1000 residents were ever-dispensed mebeverine in 1998. One-third of these mebeverine users used laxatives concomitantly. Total concomitant drug use and hospitalisations were increased in mebeverine users. The odds ratio for hospitalisations for gastrointestinal reasons was increased predominantly in mebeverine users with concomitant laxative use (OR: 8.7; 95% CI=4.3-17.3). Excess yearly costs for all concomitant medications were €94 (95% CI=€79-€109) and for hospital admissions €120 (€74-€166) per mebeverine user. In mebeverine users with concomitant laxative use these costs were €136 and €251 respectively. CONCLUSIONS: In the Netherlands only a proportion of IBS patients is treated medically. In treated patients, concomitant drug use and hospitalisations are increased relative to matched controls. Medical resource use and associated health care costs are particularly increased in mebeverine users using laxatives, indicating that constipation-predominant IBS is relative costly. The total mean excess cost per patient per year is €480.