Arthramid Slows Arthritis?

Hello Summarians!

A single intramuscular injection of betamethasone keeps cortisol suppressed in horses for up to fifteen days and may not clear competition drug testing for nearly a month.

Current withdrawal guidelines don't account for that.

Also this week: a synthetic gel injected into arthritic horse joints appears to work by reprogramming the joint's immune response at the molecular level. And a nasal tube placed before a bulldog wakes from surgery cuts the risk of serious breathing complications.

Three studies. The first one changes a number.

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Arthramid And DJD In Horses

This study investigated how intra-articular injection of 2.5% polyacrylamide hydrogel (2.5% iPAAG), a nondegradable synthetic polymer used to treat osteoarthritis (OA), influences gene expression within equine joints. Researchers induced OA in one middle carpal joint of 16 healthy horses while the opposite joint underwent a sham procedure. Two weeks after surgery, affected joints received either 2.5% iPAAG or saline, and synovial tissue and synovial fluid samples were collected over a 70-day period for transcriptomic analysis.  

The experimentally induced OA model produced substantial molecular changes characteristic of joint degeneration. Synovial tissues from untreated OA joints showed increased expression of genes involved in cell signaling, adhesion, and inflammation, while metabolic and osteogenic pathways were suppressed. Synovial fluid cells exhibited marked activation of inflammatory pathways, including tumor necrosis factor-α (TNF-α), interferon-γ, and mitogen-activated protein kinase (MAPK) signaling, particularly during the early stages of disease progression. Concurrently, pathways associated with cell cycle regulation, DNA repair, and tissue regeneration were reduced, suggesting impaired joint repair mechanisms.  

Treatment with 2.5% iPAAG significantly altered these molecular responses. In synovial tissue, iPAAG increased expression of innate immune and cell cycle regulatory pathways while suppressing metabolic, growth factor, and inflammatory signaling pathways implicated in OA progression, including MAPK, VEGF, and TNF signaling. In synovial fluid, the most pronounced treatment effects occurred two weeks after injection, when inflammatory TNF-α signaling and adaptive immune pathways involving T cells and lymphocytes were strongly downregulated. Simultaneously, genes related to extracellular matrix remodeling, collagen formation, and tissue repair were enhanced.  

The findings suggest that 2.5% iPAAG may exert its therapeutic effects by integrating into the synovial membrane, modifying immune responses, reducing inflammatory signaling, and preserving joint capsule elasticity. Although the study was limited to an acute experimental OA model, these transcriptomic data provide important mechanistic insight into how iPAAG may slow OA progression and support its clinical use in horses.

Chow, L., Contino, E., Seabaugh, K., Goodrich, L., McIlwraith, C. W., Impastato, R., Singer, J., Das, S., Dow, S., & Pezzanite, L. M. (2026). Intra-articular 2.5% polyacrylamide hydrogel alters synovial immune pathways in equine experimental osteoarthritis. American Journal of Veterinary Research https://doi.org/10.2460/ajvr.26.04.0181

Bottom line — May modify inflammation and immune response.

Nasotracheal Tubes Post Op

This retrospective study evaluated the use of nasotracheal tubes (NTTs) to provide supplemental oxygen during anesthetic recovery in 35 brachycephalic dogs undergoing surgery, primarily for brachycephalic obstructive airway syndrome (BOAS). The study aimed to assess complications and short-term outcomes when NTTs were placed either prophylactically before extubation or as a rescue measure after postoperative airway obstruction occurred.  

The population consisted mainly of French Bulldogs and English Bulldogs, many of which were considered high-risk patients based on their clinical status and BRisk scores. Most dogs underwent surgical correction of BOAS abnormalities, including stenotic nares and elongated soft palate. NTTs were inserted either before extubation in 26 dogs or after postoperative respiratory compromise necessitated reintubation in 9 dogs. Oxygen was delivered through the tubes during recovery, with tube size ranging from 8 to 12 French.  

Overall, NTTs were successful in 66% of dogs, allowing recovery without reintubation, tracheostomy, or mechanical ventilation. Success rates were higher when larger tubes (10 French or greater) were used, as all dogs receiving these larger tubes recovered successfully. Minor tube-related complications occurred in 23% of dogs and included tube obstruction, accidental dislodgement, sneezing, nasal discharge, and respiratory noise. Most complications were mild and generally well tolerated, although approximately half of the conscious dogs required light sedation to tolerate the tube.  

Non–tube-related complications were common, affecting 63% of dogs. These included regurgitation, vomiting, aspiration pneumonia, and respiratory distress. Severe complications, such as the need for temporary tracheostomy, mechanical ventilation, or death, occurred in 17% of dogs and were more common in dogs receiving rescue tubes rather than prophylactic tubes. The findings suggest that prophylactic placement of NTTs in high-risk BOAS patients may reduce the likelihood of severe postoperative respiratory complications. Overall, nasotracheal oxygen supplementation appears to be a useful and relatively safe adjunct for managing recovery in brachycephalic dogs, although additional prospective studies are needed to determine optimal timing and patient selection.

Westbrook, M., Boscan, P., Monnet, E., & Marvel, S. J. (2026). Nasotracheal oxygen supplementation facilitates anesthetic recovery in high-risk brachycephalic dogs. Journal of the American Veterinary Medical Association https://doi.org/10.2460/javma.26.02.0104

Bottom line — Early results show decreased risk Post Op.

Betamethasone Duration In Horses

This study evaluated the pharmacokinetics and pharmacodynamics of intramuscular administration of a combined betamethasone sodium phosphate and betamethasone acetate formulation in horses, an area that had not previously been investigated. Twenty-four healthy, exercised horses received a single 12 mg intramuscular dose, and blood and urine samples were collected for up to 17 days to determine drug concentrations, cortisol suppression, and effects on inflammatory mediators.  

Betamethasone was rapidly absorbed following injection, reaching a peak plasma concentration of 6.43 ng/mL approximately 45 minutes after administration. The drug exhibited a prolonged terminal half-life of about 30.5 hours, indicating sustained systemic exposure. Population pharmacokinetic modeling showed that age, sex, and body weight did not significantly influence drug disposition. Monte Carlo simulations predicted that 99% of horses would require approximately 23 days for plasma concentrations to decline below the Racing Medication and Testing Consortium screening limit of 10 pg/mL. Detectable concentrations persisted in urine for as long as 17 days in some horses, supporting the need for extended withdrawal periods before competition.  

Pharmacodynamic evaluation demonstrated prolonged biologic effects. Endogenous cortisol concentrations, a marker of corticosteroid activity, were significantly suppressed within 30 minutes of administration and remained reduced for up to 360 hours (15 days). Maximum suppression occurred 18 hours after treatment, indicating substantial and sustained hypothalamic-pituitary-adrenal axis suppression. Ex vivo analyses of inflammatory biomarkers further revealed long-lasting alterations in eicosanoid production, including changes in prostaglandins, leukotrienes, and thromboxanes, confirming prolonged modulation of inflammatory pathways. Although some inflammatory mediators initially decreased, rebound increases occurred later, suggesting complex regulation of cyclooxygenase and lipoxygenase pathways.  

Overall, the study demonstrated that intramuscular betamethasone produces prolonged systemic exposure and extended anti-inflammatory effects in horses. These findings have important implications for equine sports medicine because current withdrawal recommendations may underestimate the duration of drug activity and detection. The authors concluded that substantially longer withdrawal times should be considered to avoid positive drug tests and ensure regulatory compliance in performance horses. 

Sullivan, J., J. Blea, D. S. McKemie, P. H. Kass, and H. K. Knych. 2026. “Pharmacokinetics and Anti-Inflammatory Effects of Intramuscular Betamethasone in Exercised Thoroughbred Horses.” Journal of Veterinary Pharmacology and Therapeutics49, no. 3: 295–305. https://doi.org/10.1111/jvp.70052. 

Bottom line — Longer withdrawal times should be considered.

Just putting things in perspective …