ABSTRACT Introduction: For many years, diarrhoea has been a leading cause of millions of annual deaths in both developing and developed regions. Consequently, searching for novel sources of antidiarrheal drugs has become a key emphasis in contemporary research Aim: This study aims to evaluate the safety and antidiarrheal potential of Heliotropium indicum methanol leaf extract (HIMLE) and to formulate stable suspensions for further application. Methods: The safety and antidiarrheal potential of Heliotropium indicum methanol leaf extract (HIMLE) were assessed, and stable suspensions were formulated and characterized. Phytochemical constituents were determined using standard methods Acute toxicity testing, conducted under the Organization for Economic Cooperation and Development-423 guidelines, revealed a lethal dose (LD50) greater than 3000 mg/kg body weight (bw). Antidiarrheal effects were evaluated using a castor oil-induced diarrhoea model in Wistar rats, with groups receiving different doses of HIMLE and control. Results: The phytochemical screening revealed the presence of Flavonoids, Phenols, Tannins, Saponins, Alkaloids and Steroids. The extract demonstrated a dose-dependent reduction in intestinal transit and frequency of watery stool, with promising results compared to the positive control, loperamide. Structured vehicle suspensions, formulated at 1.25% w/v with carboxyl methylcellulose, polyvinylpyrrolidone, and tragacanth, exhibited stability over four weeks. The suspensions effectively inhibited diarrhoea in a dose-dependent manner. Formulations 4.60±2.73. 4.64±1.64 and 4.73±1.91 exhibit similar pH trends with slight variations, while Formulations 6.50±0.23 and 6.70±0.23 demonstrate higher pH values; additionally, viscosity tends to decrease as rotational speed decreases across all formulations. at 60 rpm.. Conclusion: The study suggests that HIMLE possesses significant antidiarrheal activity. The formulated suspensions proved effective in controlling diarrhoea in Wistar rats, highlighting the potential therapeutic application of Heliotropium indicum methanol leaf extract. His significant antidiarrheal activity could be accounted for by pharmacological effects. Keywords: Heliotropium indicum, methanol leaf extract, acute toxicity, structured vehicle, antidiarrhea