Pharmacokinetics of gentamicin administered intratracheally or as an inhalation aerosol to guinea pigs.

The pharmacokinetics of gentamicin were studied after intratracheal, inhalation, and iv administration to guinea pigs. Gentamicin injected intratracheally was almost completely systemically available. The comparison of the gentamicin plasma AUCs after inhalation and iv administration showed that an inhalation exposure lasting 10 min resulted in an absorption of 1.13 mg gentamicin/kg body weight into systemic circulation. This absorbed dose was 40.4 or 67.3% of the amount of gentamicin inhaled, depending on tidal volume assumed, and 1.4% of the amount of gentamicin aerosolized. The postinhalation gentamicin concentration in the lungs decreased with a half-life of 67.3 min. The data differentiate topical pulmonary gentamicin from systemic gentamicin and give a rational basis for study of the mechanism of the therapeutic effect of gentamicin inhalation aerosol in bronchopulmonary infections.