Introduction: Loperamide hydrochloride (LH) is widely used as a frontline anti-diarrheal medicine; however, the proliferation of numerous brands raises concern about its efficacy and safety. Five brands (coded A, B, C, D and E) of LH were evaluated on Castor oil induced diarrhoea and on gastro-intestinal track (GIT) motility. Each brand was represented by a group of mice while the control group received distilled water (10 ml/kg). Thirty albino mice of both sexes divided into six groups (n=5) were used for both studies respectively. Doses of 2 mg/kg of Loperamide hydrochloride and 1 mg/kg of Castor oil were administered (p. o). The ability of the brands to reduce the weight of the faeces and decrease percentage peristaltic index were recorded. The percentage reduction in the weight of faeces was in this order; A>B>E>D>C. The more the percentage reduction, the better the antidiarrheal effect of the brand. However, percentage reduction for brand C was found to be zero. Furthermore, the percentage peristaltic index for the brands was in the order; A<B<E<D<C. The smaller the peristaltic index (%) the better the anti-motility effect. Inhibition of GIT motility is the main mechanism of antidiarrheal activity of Loperamide hydrochloride. Brand C had the highest peristaltic index while brand A had the least, which confirms the results from the Castor oil induced diarrheal. Conclusion: Within the limits of this study, brand C Loperamide hydrochloride exhibited very little antidiarrheal effect. Post-market surveillance on over-the-counter (OTC) drugs like Loperamide hydrochloride should be strengthened.