Effects of normal alcohols on intestinal absorption of salicylic acid, sulfapyridine, and prednisolone in rats.

The rates of intestinal absorption of salicyclic acid, sulfapyridine, and prednisolone from solutions containing no alcohol or 0.5% ethanol, n-butanol, or n-hexanol were determined. At the concentrations used, ethanol did not significantly affect drug absorption. Butanol reduced the rate of absorption of sulfapyridine but did not significantly affect the absorption rates of prednisolone or salicylic acid. Hexanol reduced the rates of absorption of sulfapyridine and salicylic acid and increased the rate of absorption of prednisolone. The absorption-altering effects of the alcohols were concentration dependent and rapidly reversible. Histological studies indicated that the structure of the epithelium was not altered by the alcohols. While the absorption rate of water from the drug solutions was increased by the alcohols, their absorption-altering effects could not be attributed solely to increased water flux. In addition, the absorption-altering effects of the alcohols could not be attributed to formation of drug-alcohol complexes nor to alcohol-induced alterations in the extent of binding of the drugs to nondialyzable materials in the intestinal drug solution.