Abstract: Fatty acids having 8 to 14 carbon atoms, leucinic acid and nontoxic salts thereof promote the absorption of a pharmacologically-active substance through the rectum into the blood stream and effectively raise the concentration of such active substance in the blood stream even when said active substance is one which is usually absorbable through the rectum only with considerable difficulty.

Abstract: Compounds satisfying four specific requirements, namely: (1) a log P value in the range of from 2.5 to 6, (2) a molecular structure with at least one carboxyl group, (3) a pKa value for the carboxyl group of not less than 2.5 and (4) absence of halo substitution, and nontoxic salts thereof promote absorption of pharmacologically-active substance through the rectum into the bloodstream and are effective to raise the concentration of such active substance in the bloodstream even when the active substance is usually unabsorbable or absorbable through the rectum only with considerable difficulty. The compounds are combined with pharmacologically-active ingredients, with pharmaceutical bases suitable for rectal administration of drugs and with appropriate combinations of both.

Abstract: Fatty acids having 8 to 14 carbon atoms, leucinic acid and nontoxic salts thereof promote the absorption of a pharmacologically-active substance through the rectum into the blood stream and effectively raise the concentration of such active substance in the blood stream even when said active substance is one which is usually absorbable through the rectum only with considerable difficulty.

Abstract: The enamine derivatives having following formula ##STR1## promote absorption of therapeutically active substances through the digestive tract into the blood stream and are able to effectively elevate the concentration of such active substances in the blood stream even when said active substances are usually absorbable through the digestive tract only with considerable difficulty.