Synovial and serum levels of triamcinolone following intra‐articular administration of triamcinolone acetonide in the horse*

Abstract

Seven mature thoroughbred horses, weighing between 400 and 541 kg, were each injected intra-articularly into three joints with 6 mg/joint of triamcinolone acetonide (Vetalog). The fourth joint, the control, was injected with saline. Synovial fluid was taken from all four legs of the horses on days 1, 2, 3, 4, 5, 6, 7, 8, 11, and 15 following the injections. Triamcinolone acetonide was assayed by a radioimmunoassay. Blood was collected at 1, 2, 4, 6, 12 h and on days 1, 2, 3, 4, 5, 6, 7, 8, 11, and 15 following injection of either triamcinolone or saline. Both cortisol and triamcinolone were assayed. The results show that the synovial fluid level of triamcinolone was 7.5 micrograms/ml 1 day following treatment and decreased to 10 ng/ml by the 4th day. These low levels were maintained for approximately 14 days. By the 15th day, the triamcinolone was below a detectable level. Serum levels of triamcinolone increased to 3 ng/ml within 1 h and further increased to a peak of 4.3 ng/ml at 4th h. The level then decreased to 2 ng/ml at 24 h and to nearly an undetectable level in 48 h. The mean level of serum cortisol, on the other hand, gradually decreased as the serum level of triamcinolone increased. As the serum level of triamcinolone reached an undetectable level on the 2nd day, the serum cortisol level gradually increased and returned to the pre-administration level by the 5th day. These results showed that the intra-articular administration of triamcinolone maintained triamcinolone in the synovial fluid for 4-14 days and that the triamcinolone reached the blood within 1 h. The serum level of triamcinolone was maintained for 2 days and resulted in the inhibition of adrenal function for 4 days.

Anti-inflammatory and analgesic effects of intra-articular injection of triamcinolone acetonide, mepivacaine hydrochloride, or both on lipopolysaccharide-induced lameness in horses

“…These findings are in accordance with those of another study 24 in which TA (6 mg) was injected into each of 3 separate equine joints and detected at low concentrations in those joints for up to 14 days and in plasma for at least 48 hours. Triamcinolone acetonide was detected in serum at low concentrations 12 hours after administration, regardless of whether mepivacaine was coadministered, but TA was not detected in serum 5.5 days after administration.…”

“…23 Similarly, ongoing anti-inflammatory or analgesic effects may not be totally dependent on the detectable ex-istence of analgesic (TA) in synovial fluid or plasma 20,24 but rather on the effect created at the cellular level 46 and the continued occupation of cell receptors. Such an influence reportedly affects both the ipsilateral (treated) and contralateral (nontreated) MCP joint.…”

“…17 In clinical practice, the ability to administer 1 intra-articular injection of a combination of TA a and mepivacaine b would be useful for confirming the site of lameness and treating any synovitis or arthritis that existed there. 24 To our knowledge, the effects of 1 TA injection or TA combined simultaneously with other medications injected into 1 joint of a horse have not been evaluated. 18,19 Triamcinolone acetonide has recently become popular as an intra-articular medication for high-motion joints because of its purported chondroprotective and anti-inflammatory properties.…”

Pharmacokinetics of triamcinolone acetonide following intramuscular and intra‐articular administration to exercisedThoroughbred horses

“…Chen et al . reported maximal concentrations of 4.3 ng/ml at 4 h post administration following an intra‐articular dose of TA (6 mg) administered at 3 different sites with plasma concentrations at almost nondetectable levels by 2 days post administration .…”

Pharmacokinetics and pharmacodynamics of dexamethasone after oral administration in apparently healthy horses

“…2,[4][5][6][7] The genomic effects of glucocorticoids generally require a period of hours to days to become detectable, and in recent years, nongenomic pathways have been recognized as having an important role in the more rapid onset of glucocorticoid effects. 14,16,18,19 To the authors' knowledge, the pharmacokinetics and pharmacodynamics of PO administered dexamethasone solution in horses have not been completely determined. 6,8 Dexamethasone, a fluorinated analog of prednisolone, has a longer duration of activity and is approximately 30 times as potent as endogenous cortisol.…”