Public Release: 

New study funded by Morris Animal Foundation demonstrates loss of drug potency

Researchers find decreased potency of doxycycline after 21 days

Morris Animal Foundation

DENVER/December 7, 2017 - Drugs work best when their potency remains stable or consistent, but a new study funded by Morris Animal Foundation shows a commonly compounded antimicrobial drug used in veterinary medicine may be losing potency over time. The study recently was published in the Journal of the American Veterinary Medical Association.

Doxycycline is used to treat a number of bacterial infections in cats and dogs. Veterinarians often request compounded formulations of doxycycline because large tablets can be difficult for owners to give to pets, or there is a lack of FDA-approved doxycycline product available. The research team at Kansas State University showed that compounded formulations of doxycycline lost potency within three weeks of receipt, with many dropping to sub-therapeutic content in that time, as defined by the United States Pharmacopeia (USP) standards.

The findings could have a significant impact for practicing veterinarians who rely on this antimicrobial to treat a variety of infectious diseases in animals including Rocky Mountain spotted fever and leptospirosis, and as an adjunct therapy for heartworm disease.

"These study results have important ramifications for practicing veterinarians," said John Reddington, DVM, PhD, President and CEO of Morris Animal Foundation. "The study helped fill in a knowledge gap about compounded medications, and may lead to additional studies on this important but often overlooked topic."

The research team at Kansas State University included Tanner Slead, a Morris Animal Foundation Veterinary Student Scholar, and his mentor, Dr. Kate KuKanich.

The team compared FDA-approved formulations of doxycycline with compounded doxycycline obtained from three national compounding pharmacies. They measured doxycycline content one day after receipt of medication, and again at day 21. Their findings showed that the potency of drug varied between preparations at both time points.

Dr. KuKanich noted, "All of the FDA-approved products met USP standards at both time points and are currently available and cost-effective; therefore they are the formulations of choice. If the FDA-approved drugs are not feasible, then compounded tablets would be the next best choice. Based on this study, we recommend avoiding compounded chews and liquid formulations. Although this was a relatively small study with only three pharmacies used, the results are consistent with results of random testing of other compounded products."

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About Morris Animal Foundation

Established in 1948, Morris Animal Foundation is dedicated to improving and protecting the health of animals through scientific innovation, education and inspiration. Our investment in research has yielded life-saving vaccines, new treatments for critical diseases, superior screening tests, and advanced diagnostic tools. We respond to emerging animal health threats that endanger entire species, and make new discoveries in basic animal biology to support applied research. With every study we fund - more than 2,600 to date - we strive to advance the science of veterinary medicine, honoring the founding principles of Dr. Mark L. Morris Sr., and benefitting animals worldwide.

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