[Examinations on the pharmacokinetics and compatibility of enalapril in racing pigeons]

It was the aim of this study to examine the compatibility and the pharmacokinetics of the angiotensin converting enzyme inhibitor enalapril after oral application in racing pigeons and Amazons, and to contribute to a safe dosage regime of this drug in birds.

For the examination of drug compatibility, three groups of pigeons (n = 8 each) received enalapril into the crop at a dose of 5 or 10 mg/kg body weight, or placebo, respectively. Health status, and water and food consumption were monitored regularly, and clinical, hematological and blood-chemical parameters were determined. To determine a suitable starting dosage, birds were treated with enalapril at a dose of 2.5 mg/kg (first trial) and 1.25 mg/kg (second trial), and blood samples were collected at defined time points. Using high performance liquid chromatography (HPLC), the enalapril concentration in the plasma samples was determined.

Drug application did not cause any significant drug-related difference between the groups. Nearly all measured parameters were found to be within normal physiological ranges. Only for hematocrit was a slight but significant increase found for the group treated with 5 mg/kg enalapril. In pigeons, after application of 2.5 mg/kg enalapril, the maximum plasma concentration was found in the first sample taken (388.2 ± 174.1 mg/kg). The application of 1.25 mg/kg resulted in a maximum concentration of 116.1 ± 70.2 ng/ml after 30 minutes in pigeons. In the Amazon birds, the maximum value was found after 1 hour (first sampling) of 43.3 ±6.0 ng/ml. In all examinations, the enalapril concentration was <15 ng/ml after 8 hours. The terminal half-life was 2.68 hours for pigeons and 2.36 hours for Amazons.

The results underline the good compatibility of enalapril after oral administration in healthy pigeons. A starting dosage of 1.25 mg/kg enalapril given twice daily can be recommended.

The study provides basic data (compatibility and pharmacokinetics) for the application of enalapril in birds such as the racing pigeon.