Oral prednisolone achieves measurable concentrations in equine synovial fluid within 3 hours of administration: Preliminary observations

Background: Clinical and anecdotal evidence exists for the use of orally administered prednisolone in the treatment of osteoarthritis in human patients; however, prednisolone is not commonly prescribed by this route of administration in horses for the treatment of osteoarthritis. Objectives: This preliminary study tested the hypothesis that orally administered prednisolone could be detected in equine synovial fluid 3 h after administration. Study design: Pre/post study. Methods: Six horses were used in this study. Blood was drawn pre-prednisolone administration to assure that all horses were prednisolone free. Three hours after being given 400 mg prednisolone per os, an additional blood sample was taken, as well as samples from the radiocarpal (RC) and tibiotarsal (TT) joints. Samples were frozen and sent to the laboratory for the determination of the presence of prednisolone using liquid chromatography tandem mass spectrometry. Results: Prednisolone appeared in measurable concentrations in the blood (Mean = 92.655 ng/mL; SD = 54.95 ng/mL) and synovial fluid (RC Mean = 28.44 ng/mL; SD = 20.58 ng/mL and TT Mean = 20.33; SD = 15.67 ng/mL) of all horses when tested 3 h after administration. Main limitations: This study did not test for any possible therapeutic effects of oral prednisolone in osteoarthritis. It did not attempt to establish a therapeutic dosage for the medication, nor did it attempt to establish the pharmacokinetics of the medication. Conclusions: Orally administered prednisolone appears in equine blood and synovial fluid at 3 h post-administration. Since it appears in joint fluid at concentrations that have been shown to be therapeutic for other corticosteroids, orally administered prednisolone may have potential value as a therapeutic agent in the treatment of equine osteoarthritis.