Background: Caesarean section of bitches is a well recognized painful condition in dogs and it can be classified as a soft tissue surgery. Cimicoxib, a newly registered NSAID in European Union has a claim for the relief of pain in peri-operative conditions. However, in case of caesarean section, the main concerns of using NSAIDs are the transfer of the drugs into milk and its impact on the suckling pups. Thus, the aim of the present work was to evaluate the transfer of cimicoxib into the milk of 6 lactating bitches after a single oral administration of the drug on day 0 (just after whelping) and on day 28 at the target dose of 2 mg/kg. Another aim of the study was to evaluate the transfer of the drug from the milk into the suckling pups. Blood and milk samples were collected from the bitches after each administration on day 0 and day 28 and blood samples were drawn from the pups after suckling on day 28.
Results: All bitches whelped without any complication and gave birth to 38 pups. After administration on D0, the mean observed plasma Cmax in bitches was 0.5323 μg/mL and the mean area under the concentration-time curve extrapolated to the infinity, AUCINF, was 2.411 μg.h/mL. After administration on D28, only AUCINF was significantly higher with a value of 3.747 μg.h/mL. In milk, after administration on D0, the mean observed Cmax was 0.9974 μg/mL and the mean area under the concentration-time curve until the last measurable time point, AUClast, was 4.205 μg.h/mL. Out of 24 sampled pups on D28, only 2 animals had a sample with very low cimicoxib concentrations slightly above the limit of quantification (0.01 μg/mL).
Conclusion: The presented data show that cimicoxib given by oral route to lactating bitches at a single dose of 2 mg/kg had a high transfer rate into the milk with a milk to plasma ratio of 1.7 to 1.9. The transfer rate to the suckling pups was low and no clinical abnormalities were detected in both bitches and pups.