The Pathophysiology of Diarrhoea

Effects of a non-absorbable osmotic load on drug absorption in healthy volunteers

1. We have studied the effects of a non-absorbable osmotic load on the absorption of a multicomponent solution of frusemide, atenolol, hydrochlorothiazide and salicylic acid in six healthy volunteers. 2. Each subject was studied on up to four separate occasions. The drugs were administered in one of four solutions: a) a mannitol/electrolyte solution, b) a double-strength mannitol/electrolyte solution, c) a glucose/electrolyte solution and d) water. Lactulose or sulphasalazine were added as oro-caecal transit markers. Lactulose was included in the mannitol- and glucose-based solutions, adding a further non-absorbable osmotic load, and sulphasalazine was added to the water, adding little osmotic load. 3. The absorption of atenolol and hydrochlorothiazide was two- to three-times less from all lactulose-containing solutions than from the sulphasalazine-containing solution. The absorption of frusemide and salicylic acid was similar from all four solutions. 4. The largest non-absorbable osmotic load impaired the absorption of atenolol and hydrochlorothiazide most and the incorporation of glucose only partly restored absorption. 5. These results suggest that transmucosal water movement is an important determinant of atenolol and hydrochlorothiazide absorption but is less relevant for the absorption of frusemide and salicylic acid. Furthermore, these data demonstrate a previously unrecognised interaction between a commonly prescribed laxative--lactulose, and atenolol and hydrochlorothiazide.

Normalization of small intestinal propulsion with loperamide-like antidiarrheals in rats

Gastrointestinal propulsion and the presence of diarrhea were assessed in rats pretreated with various opioids and challenged orally with either castor or paraffin oil, which both contained phenol red as a marker of gastrointestinal propulsion. In solvent-pretreated rats, diarrhea was always observed within 90 min after castor oil, reflecting a state of hyperpropulsive activity of the gut, but never (up to 8 h) after paraffin oil, reflecting normal intestinal propulsion (which amounted to an average distance of 91% of the total length of the small intestine in 90 min). Paraffin oil propulsion was blocked (to values less than 60%) by all opioids tested with the exception of the gut-selective compounds loperamide, loperamide oxide and fluperamide oxide (ED50s: greater than or equal to 160 mg/kg). Castor oil diarrhea was antagonized by all opioids tested and, at comparable but slightly (1.3-2.6 times) higher doses, propulsion was normalized to values (less than 100%) comparable to those measured in paraffin oil-challenged control rats. Castor oil propulsion was further reduced to subnormal values (less than 60%) by still higher doses of the opioids, comparable to those that blocked propulsion after paraffin oil. However, the required dose increment varied consistently among the opioids tested and ranged, depending on gut selectivity, from a factor 2.3 times the antidiarrheal dose for narcotic analgesics such as pethidine and dextromoramide to greater than 300 for antidiarrheals such as loperamide, loperamide oxide and fluperamide oxide. Protection from diarrhea and normalization of propulsion showed a close correlation; both failed to correlate with central analgesic activity and are thought to be mediated via peripheral opioid receptors.(ABSTRACT TRUNCATED AT 250 WORDS)

Pulmonary excretion of H2 in calves with Cryptosporidium-induced malabsorption

Pulmonary hydrogen gas (H2) concentrations were used to assess the malabsorption of dietary nutrients in preruminating calves inoculated with Cryptosporidium sp. Normal values were established in five control calves and seven calves (principals) were inoculated with 1.0 x 10(8) Cryptosporidium sp. oocysts. Hydrogen concentrations and wet fecal weights were measured at three stages: before Cryptosporidium sp. inoculation (stage 1), three days after the onset of diarrhea (stage 2), and after the resolution of diarrhea (stage 3). Mean end-breath and total-breath H2 concentrations in the principal calves were higher (P less than 0.025 and P less than 0.05) for stage 2, when compared to control values. Both end-breath and total-breath H2 concentrations were increased (P less than 0.001 and P less than 0.025, respectively) in the principal calves during stage 2 when compared to values obtained for stages 1 and 3. Concurrently, Cryptosporidium sp. infection was associated with increased (P = 0.06) fecal output during stage 2, only. The increased H2 concentrations and cumulative fecal output show that Cryptosporidium sp. caused malabsorption of fermentable nutrients.

Virally induced alterations in cellular permeability: a basis of cellular and physiological damage?

Virally induced permeability changes occur when haemolytic paramyxoviruses are added to cells; similar (though not identical) changes take place during infection of cells with viruses from several families (including paramyxoviruses). These changes occur in intact, viable cells, and precede subsequent cytopathic effects, to which they are likely to contribute. There is accumulating evidence to suggest that virally induced permeability changes may also underlie the physiological and clinical consequences of viral infection in certain situations.