AIM: Racecadotril is a specific enkephalinase inhibitor that exhibits intestinal antisecretory activity without affecting intestinal transit. Loperamide is an effective anti-diarrheal agent, but it usually induces constipation. This study is to compare the efficacy, safety, and tolerability of racecadotril versus Ioperamide in the outpatient treatment of acute diarrhea in adults.METHODS: A two-center, randomized, parallel-group,single-blind study was carried out to compare the efficacy,tolerability, and safety of racecadotril (100 mg thrics daily)and Ioperamide (2.0 mg 2 twics daily) in 62 adult patients suffering from acute diarrhea. The main efficacy criterion used was the duration of diarrhea after beginning the treatment (in hours). Other signs and symptoms were also evaluated.RESULTS: The clinical success rates for these antidiarrheal treatments were 95.7% and 92.0% for racecadotril and Ioperamide respectively. Patients on racecadotril had a median duration of diarrhea of 19.5 h compared with a median of 13 h for patients on Ioperamide.Rapid improvement in anal b and nausea was found for each drug. However, more patients on Ioperamide suffered from reactive constipation (29.0% vs 12.9%).Itching, another adverse event was notably higher in the racecadotril group (28.6% vs 0%). With regard to other adverse events, the two medications showed similar occurrence rates and similar concomitant medication usage rates.CONCLUSION: Racecadotril and Ioperamide are rapid,equally effective treatments for acute diarrhea in adults,but Ioperamide treatment is associated with a higher incidence of treatment-related constipation.