Effects of oral administration of metronidazole and doxycycline on olfactory capabilities of explosive detection dogs was published in the American Journal of Veterinary Research in August 2016, authors Eileen K. Jenkins, DVM MS, Tekla M. Lee-Fowler, DVM MS, et al.
The drugs were given separately to 18 explosives detection dogs with a 10-day wash-out period in between each drug. Of the 18 dogs, 9 (50%) had a degradation of performance in response to 1 or more of the 3 explosives used for detection when administered metronidazole at 25 mg/kg twice daily for 10 days. No significant degradation occurred with doxycycline administration at 5 mg/kg twice daily for 10 days. The authors concluded that at the given dose, metronidazole may adversely affect the ability of these dogs to detect the tested explosives. Doxycycline at the given dose appeared safe for use.
Details of the research may be found in the Am J Vet Res 2016;77:906-912