title: Pulmonary absorption of drugs in the neonatal rat.
abstract: To compare the pulmonary absorption of drugs in newborn rats (3-27 days old) with that  in adults, 0.01-0.1 ml of Krebs-Ringer phosphate solution (pH 7.4) containing a drug was administered to anesthetized animals by way of a catheter introduced through a tight-fitting tracheal cannula. After various times, lungs and trachea were removed and assayed for drug that remained. Semilogarithmic plots of percent drug remaining against time yielded a straight line for each compound. The lipid-soluble drugs procaine amide and sulfisoxazole were absorbed at similar rates in newborn and adult rats. In contrast, the lipid-insoluble drugs tetraethylammonium, p-aminohippuric acid, and mannitol were absorbed approximately 2 times more rapidly in younger rats (3-12 days) than in older animals (18 day, 27 day, or adult). The results suggested that the respiratory tract membranes of 3- to 12-day-old rats have a greater porosity than those of older animals.
mesh_terms: D000042:Absorption; D000375:Aging; D000818:Animals; D000831:Animals, Newborn / Q000378:metabolism*; D005260:Female; D008168:Lung / Q000378:metabolism*; D008297:Male; D009994:Osmolar Concentration; D004364:Pharmaceutical Preparations / Q000378:metabolism*; D051381:Rats; D012737:Sex Factors
chemical_list: D004364:Pharmaceutical Preparations