Pulmonary delivery of a dopamine D-1 agonist, ABT-431, in dogs and humans

The purpose of this study was to evaluate the feasibility of intrapulmonary delivery of ABT-431, a selective D1 receptor agonist. Following intratrach eal instillation of the drug solution, the lung bioavailability was found t o be approximately 75% in dogs. An aerosol suspension formulation was then developed by dispersing the drug in tetrafluoroethane, HFC-134a, with the a id of poloxamer 124 and vitamin E. This ABT-431 MDI aerosol formulation sho wed about 40% of the particles emitted from the valve and actuator system t o be under 5 mu m in diameter. Also, the primary package (15 mt aluminum co ntainer, DF10/ACT-150 valve, and Micron-4-actuator with the orifice 0.4 mm) was satisfactory for accurate and reproducible dosimetry. Using tracheosto mized beagle dogs, the C-max following tracheal administration of 5 mg aero solized ABT-431 was found to be 13.3 +/- 0.9 ng ml(-1) and the AUC(0-24) wa s estimated at 33.2 +/- 10.6 h ng ml(-1). The lung bioavailability of the a erosolized drug was 34% compared to intravenous injection in dogs. In human s, results from a single rising dose study demonstrated that rapid absorpti on of ABT-431 following oral inhalation administration resulted in a dose-d ependent increase in the area under the plasma-time curve at dosage levels between 3.3 and 13.2 mg. There is a possibility of up to 25% absorption of the drug from human lung. Thus, pulmonary bioavailability of ABT-431 is sig nificantly greater than that of oral administration. Also, these findings s uggest that small and lipophilic compounds, especially with hepatic first p ass effect, may be effectively delivered systemically using oral inhalation aerosols. (C) 1999 Elsevier Science B.V. All rights reserved.