Inhibition of Microlax-induced experimental diarrhoea with narcotic-like extracts of Psidium guajava leaf in rats.

Measurement of rates of propulsion in the small intestine in control and experimental groups of male Sprague-Dawley rats (200-250 g) were carried out as a means of assessing antidiarrhoeal activity of aqueous extracts of the leaf of Psidium guajava (L.), using morphine as the standard drug of reference. Hyperpropulsion (diarrhoea) was induced by gavaging rats in a control group with Microlax, using phenol red mixed into it as a marker in the intestine, and the mean rate of the hyperpropulsion was determined. The normal rate of propulsion, defined as the percentage of the length of the ileum traversed by the front of the dye in 1 h after gavaging animals with a liquid paraffin-phenol red meal, was also determined in another control group. In experimental groups pretreated with enteral administration of either morphine or aqueous extracts, 1 h before the challenge with Microlax, the percentage inhibition to the hyperpropulsive rate (antidiarrhoeal activity) was calculated. Both morphine and the extracts produced a dose-response relationship in their antidiarrhoeal effects. A dose of 0.2 ml/kg fresh leaf extract produced 65% inhibition of propulsion. This dose is equiactive with 0.2 mg/kg of morphine sulphate. The antidiarrhoeal action of the extract may be due, in part, to the inhibition of the increased watery secretions that occur commonly in all acute diarrhoeal diseases and cholera.