The effect of osmotic pressure on the intestinal absorption of sulfafurazol and ethanol in the rat.

The aim of the present study was to extend our earlier research into the effect of osmotic pressure on the intestinal absorption of drugs. In the experiments rats and an in situ technique were used. Sulfafurazol and ethanol were test substances and osmotic pressure was adjusted by NaCl, KNO3 or Na2SO4. From the results it was concluded that if all other factors are excluded the effect of the osmotic pressure of the vehicle is such that an isotonic solution has the best extent of bioavailability. Bioavailability decreases both when osmotic pressure decreases and when it increases. However, the decreasing effect of hypertonic solutions is stronger than that of hypotonic solutions. Although NaCl, KNO3 and Na2SO4, are often mentioned as alternative salts for adjusting osmotic pressure they are not equal in respect of their ability to alter the absorption of a drug.