Comparison of various doses of carbon 13-labeled aminopyrine for a carbon 13-labeled aminopyrine demethylation blood test in healthy dogs.
OBJECTIVE
To determine an optimal dose of carbon 13 ((13)C)-labeled aminopyrine for use in a (13)C-aminopyrine demethylation blood test in healthy dogs.


METHODS
9 adult dogs.


METHODS
Food was withheld from each dog for 12 hours. A 2-mL baseline blood sample was obtained from each dog and placed into an evacuated tube containing sodium heparin. Carbon 13-labeled aminopyrine was administered IV at doses of 1, 2, 5, or 10 mg/kg. Additional blood samples (2 mL) were obtained and placed into evacuated tubes containing sodium heparin 30, 45, 60, and 75 minutes after (13)C-aminopyrine administration. Hydrochloric acid was used to extract CO(2) from blood samples. The extracted gas was analyzed by fractional mass spectrometry to determine the percentage dose of (13)C administered as (13)C-aminopyrine and recovered in extracted gas (PCD).


RESULTS
Gross evidence of clinical adverse effects was not detected in any dog after administration of (13)C-aminopyrine. The mean coefficient of variation (CV) for PCD was significantly lower than the mean CV for the summation of PCD values up to a given sampling time (CUMPCD). Mean PCD values among the 4 doses for each sample time were not significantly different. Administration of (13)C-aminopyrine at a dose of 2 mg/kg resulted in the lowest interindividual variability.


CONCLUSIONS
The PCD is superior to CUMPCD for the quantification of aminopyrine demethylation. Administration of (13)C-(13)C-aminopyrine at a dose of 2 mg/kg is appropriate for use in the (13)C-aminopyrine demethylation blood test in healthy dogs.
Moeller
E Michael
EM
Gastrointestinal Laboratory, College of Veterinary Medicine, Texas A&M University, College Station, 77843, USA.
Steiner
Jörg M
JM
Williams
David A
DA
Tetrick
Mark
M
Burr
John
J
D000632:Aminopyrine / Q000009:adverse effects / Q000378:metabolism*; D000818:Animals; D002247:Carbon Isotopes; D018592:Cross-Over Studies; D004283:Dog Diseases / Q000175:diagnosis*; D004285:Dogs; D004305:Dose-Response Relationship, Drug; D005260:Female; D006262:Health; D008107:Liver Diseases / Q000175:diagnosis / Q000662:veterinary*; D008111:Liver Function Tests / Q000379:methods / Q000662:veterinary*; D008297:Male; D008745:Methylation
D002247:Carbon Isotopes; D000632:Aminopyrine