Introduction: Estimation of possible cardiovascular side effects belongs to the safety assessment of every drug candidate. This paper describes a new strategy for treating conscious labrador dogs with drugs by inhalation using a specially designed mask and a novel inhaler device.
Methods: Labrador dogs (male or female) were used that had transducers implanted for the measurement of left ventricular and descending aortic blood pressures and an ECG for use together with a telemetry system. Administration by inhalation was achieved using a novel delivery device. The Respimat device is a propellant-free inhaler to deliver aerosols from solutions. The new system was evaluated using Formoterol with four dogs using a 4 x 4 Latin square design. Three doses of Formoterol (0.6, 1.2, and 2.4 microg/kg, dissolved in 60% ethanol) were administered by inhalation together with a vehicle (60% ethanol) treatment by applying three inhalations, each consisting of 10 microl solution.
Results: Formoterol increased HR, QRS-interval, QT-interval, and LVPdP/dtmax and dose-dependently decreased systolic and diastolic BP. This effect lasted up to 14 h.
Discussion: Drug administration by inhalation in the conscious labrador dog using the Respimat is a useful new model for safety pharmacology studies of new drug candidates that are intended to be given by inhalation in the clinic.