A total of 203 patients referring with constipation were evaluated during the study period from which 128 patients were eligible and willing to participate in the study. Finally, 110 patients participated and started the medication. During the 4-week study duration 67 patients dropped-out of the study (Fig. 1). Compared with patients who remained in the study, those who discontinued the study were younger (difference 5.2 ± 2.2 years, P = 0.024), but not significantly different regarding symptoms (P > 0.05). Considering these drop-outs during the study period, all analyses were performed based on the ITT principles. Demographic characteristics are summarized in Table 1. The two groups were not similar regarding some of the baseline symptoms’ characteristics as presented in Table 2. Accordingly, the baseline values of the outcome variables were considered as covariates and controlled in the analyses.