ABSTRACT
<p><b>OBJECTIVE</b>Acute diarrhea is one of the major illnesses that cause death in children, despite clinical interventions and the use of oral rehydration therapy. Thus, there is need to discover other effective, affordable and accessible treatments for this disease. Therefore, this study was carried out to investigate the effects of hexane extract of Citrus limon peel (HECLP) on castor oil-induced diarrhea in rats.</p><p><b>METHODS</b>Diarrhea was induced in male albino Wistar rats weighing 100-150 g. The antidiarrheal activity of HECLP at different oral dosages (5, 10 and 20 mg/kg) was investigated by counting the number of wet fecal pellets. Animals were further treated with propranolol, prazosin, nifedipine and atropine to assess the effects of receptor blockers on the activities of the extract. The effects of HECLP on castor oil-induced enteropooling and the intestinal transit time of activated charcoal were also evaluated.</p><p><b>RESULTS</b>Each of the 3 doses of C. limon significantly reduced (P < 0.05) the number of wet fecal pellets produced by animals, with 20 mg/kg HECLP producing the highest percentage inhibition (34.2%). Wet fecal pellet inhibition by the standard drug loperamide (3 mg/kg p.o.) was 68.4% relative to the negative control. Blockage of β adrenergic receptors by propanolol abolished the antidiarrheal effects of HECLP. Intestinal fluid accumulation was inhibited by 68.7% and 78.5% by 20 mg/kg HECLP and loperamide respectively. Furthermore, 20 mg/kg HECLP significantly (P < 0.05) reduced the percentage intestinal transit time (21.4% ± 1.42%), relative to the control (34.2% ± 4.29%); atropine (5 mg/kg, intraperitoneal injection) significantly (P < 0.001) reduced the percentage intestinal transit time to 11.2% ± 0.85%.</p><p><b>CONCLUSION</b>These results suggest that C. limon peel possesses antidiarrheal effects through antisecretory and antimotility mechanisms that act through the β adrenergic system.</p>