Doxycycline is an antibiotic used to treat Lyme disease, Ehrlichia and a variety of other bacterial infections. The drug is also known to have activity against MMP enzymes — matrix metalloproteinases.
MMPs are enzymes found throughout the body tissues. Their function is to break down connective tissues, either as part of normal body processes and repairs, or in response to inflammation. Since connective tissue is found virtually anywhere, a wide variety of conditions involve MMP activation.
It’s been known for a long time that doxycycline and related drugs can slow the destruction caused by arthritis. Recent research in horses has confirmed doxycycline reaches levels in joints sufficient to suppress MMPs.
”Doxy” has also been effective in relieving pain in laminitic horses and DSLD horses that didn’t respond well to Jiaogulan and arginine alphaketoglutarate. Some types of corneal ulcers/inflammation can also be treated with doxycycline as well as other MMP inhibitors.
Bottom Line: The advantages are that doxycycline is given orally, is relatively inexpensive and doesn’t carry the risk of colonic and/or gastric ulcers associated with nonsteroidal anti-inflammatory drugs. The MMP inhibiting dose is only half of that needed to treat infections, 5 mg/kg, given twice a day (total daily dose 10 mg/kg).
If your horse has a problem that may benefit from this effect, talk to your vet. Doxycycline is a prescription medication.