Fluorocarbon aerosol propellants X: pharmacokinetics of dichlorotetrafluoroethane in dogs.

An intravenous dosage form of dichlorotetrafluoroethane, a common fluorocarbon aerosol propellant, was formulated in polyethylene glycol 400 for single dosing to unanesthetized dogs. A three-compartment open model was proposed for the disposition of this compound in dogs, with average half-lives of 1.3, 9.6, and 50.8 min for the three disposition phases. An analysis of tissue compartment distribution following a single dose showed that it took about 2 hr to achieve pseudo-distribution equilibration, following which more than 90% of the propellant remaining in the body was retained in the tissue compartments. Pulmonary clearance and volumes of distribution were calculated considering the first-pass effect through the lungs. The volume of distribution was approximately 10 times the body weight in terms of blood concentration, and about 84% of the propellant was cleared from the blood passing through the lungs in each cycle.