The primary objectives of these studies were to determine the clinical efficacy and safety of the potential antisecretory and antimicrobial drugs in the treatment of diarrhoea due to Vibrio cholerae and enterotoxigenic Escherichia coli (ETEC). The drugs evaluated were chlorpromazine (CPZ), nicotinic acid, berberine, indomethacin, chloroquine, tetracycline, furazolidone, and bioflorin. Additionally, the role of prostaglandins (PGs) in the pathogenesis of cholera diarrhoea has been studied. The drug studies were carried out as placebo-controlled, randomized clinical trials in patients with active diarrhoea due to vibrio cholerae and ETEC. All patients received intravenous (i.v.) or oral rehydration solutions (ORS), but no other medications except the study drugs. Results indicate that CPZ (1 mg/kg or 4 mg/kg), berberine (200 mg), and nicotinic acid (2 g) all reduced stool volumes from 30% to more than 50% in diarrhoeal patients without significant side effects. It appeared that berberine was more effective in ETEC diarrhoea than in cholera. However, chloroquine, indomethacin, clonidine, and bioflorin had no clinically useful effects. Among the antimicrobial agents, a single dose of tetracycline was found to be effective in cholera, because the drug significantly (p < 0.05) reduced the total stool volume from 20.9 +/- 15.9 to 10.5 +/- 8.6 (liters in 6-days, mean +/- SD) compared to furazolidone. Drugs other than antimicrobial and antisecretory agents were also evaluated in the treatment of cholera. It has been shown that treatment with bioflorin, which is a bacterial preparation of lyophilized Streptococcus faecium, did not significantly (p > 0.05) reduce fluid-loss in cholera. Additional studies in animals indicated that treatment with short chain glucose polymers, alone or in combination with a chloride blocking agent, anthracene-9-carboxylic acid (A9C), significantly reduced intestinal secretion in a rat model of secretory diarrhoea. For the first time it was demonstrated that jejunal prostaglandin (PG) E2 concentrations were significantly increased during acute cholera and correlated with the volumes of stool and duration of diarrhoea. Furthermore, it was shown that treatment with indomethacin, a potent inhibitor of PG synthesis, significantly reduced jejunal PGE2 output in adults with acute cholera, in addition to net secretion of water and electrolytes. In summarizing the results, it is concluded that: (1) CPZ, berberine, and nicotinic acid are potential antidiarrhoeal agents, (2) PGs are involved in the pathogenesis of cholera, (3) tetracycline and furazolidone are effective antimicrobial agents in cholera, (4) and glucose short-chain polymers (used with the chloride blocking agent, anthracene-9-carboxylic acid) are better sources of carbohydrates in oral rehydration solutions.