Oxycodone and Dogs

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I appreciate your support. This newsletter is an attempt to help us all with the deluge of information we face daily. It will usually contain 3 summaries and citations that have to do with animal health.

Some of these topics are theoretical and some could be implemented today. The goal is to keep you up to date with current trends and topics.

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Vitamin E and the Sick Horse

This study investigated vitamin E (α-tocopherol) levels in hospitalized horses to determine whether the micronutrient’s concentration declines during hospital stays as it often does in critically ill human patients. Vitamin E, an essential lipophilic antioxidant, is known to protect the central nervous system and combat oxidative damage—a factor implicated in various critical illnesses. Although human studies have shown that vitamin E levels can drop significantly during hospitalization due to factors such as increased metabolic consumption and reduced intake, the dynamics in horses have not been similarly evaluated. 

In this research, serum vitamin E concentrations were measured at admission and discharge in a cohort of horses, including both adults and foals, admitted for at least five days. Despite the expectation that the lack of access to fresh grass—a key dietary source of vitamin E—might lead to declining levels, the study found that overall vitamin E concentrations were not significantly affected by hospitalization. Approximately 12.7% of all horses, and 16.7% of those hospitalized for five or more days, were found to be deficient upon admission. Notably, even among deficient animals, many showed improvements by the time of discharge without receiving supplementation, and horses with neuromuscular signs such as ataxia did not have vitamin E deficiency. 

The variability in vitamin E intake was highlighted by differences in feed sources and methods of hay harvest, which can lead to fluctuating serum levels. The study also discussed how management practices, such as the use of commercially formulated feeds and occasional plasma transfusions in foals (especially those with failure of passive transfer), might influence the observed vitamin E concentrations. Although most hospitalized horses maintained adequate levels during their stay, the relatively high prevalence of deficiency in this referral hospital population—located in a region known for good pasture and nutrient-rich hay—suggests that vitamin E deficiency might be even more common in settings with limited pasture access or lower-quality forage. 

While the findings do not support routine vitamin E supplementation for all hospitalized horses, they underscore the importance of monitoring serum vitamin E levels, particularly in cases where clinical signs of deficiency are evident or where nutritional management might predispose horses to lower levels. The study also acknowledged its limitations, including a small sample size, exclusion of horses already on supplementation, and the potential influence of regional dietary factors, which may limit the generalizability of the results. 

Palmisano, M. G., Colmer, S. F., Saw, Y. L., Xu, X., Stefanovski, D., Murphy, L., & Johnson, A. L. (2025). Vitamin E concentrations in hospitalized adult horses and foals. Journal of the American Veterinary Medical Association https://doi.org/10.2460/javma.24.09.0590 

Bottom line — Something to monitor in the sick horse.

Oxycodone in Dogs

This study evaluated the pharmacokinetics and physiological effects of a single oral dose of oxycodone in dogs, exploring its potential as an outpatient analgesic for post‐operative or cancer pain management. Five healthy, 2-year-old, castrated male hounds participated in a randomized, crossover trial. Each dog received a standard meal either with or without immediate-release oxycodone at 1 mg/kg, with treatments separated by a one-month washout period. Blood samples were collected at intervals ranging from 15 minutes to 8 hours post-administration, and plasma oxycodone concentrations were measured using ultra-high-pressure liquid chromatography coupled with mass spectrometry. Vital signs were also monitored to assess physiological responses. 

Pharmacokinetic analysis using non-compartmental methods revealed a maximum plasma concentration (Cmax) of 58.6 ng/mL, reached at a time (tmax) of approximately 1.5 hours after dosing. The elimination half-life (t1/2el) was found to be about 2.6 hours, with an area under the plasma concentration–time curve (AUC0-t) of 236.1 ng·h/mL, and a mean residence time (MRT) of 3.9 hours. Based on these data, computer simulations predicted that dosing at 1 mg/kg orally every 6 hours would result in a steady state with a peak concentration (Cmax) of roughly 69.4 ng/mL and a trough concentration (Cmin) of approximately 17.0 ng/mL. 

Assuming that the minimum effective analgesic concentration is similar between humans and dogs (around 25 ng/mL), the simulations suggest that while therapeutic levels are reached transiently, maintaining analgesia would likely require dosing more frequently than every 6 hours. Additionally, the study noted that oxycodone administration resulted in a significantly lower rectal temperature at 1 and 4 hours post-dose, indicating a measurable physiological side effect that may warrant further investigation. 

Militana, E., Schwark, W., Flanagan, A., Pan, Z., Riley, E., Sorge, C., Gleed, R.D. and Boesch, J.M. (2025), Pharmacokinetics and Physiological Effects of a Single Oral Dose of Oxycodone in Healthy Dogs: A Pilot Study. J Vet Pharmacol Therap. https://doi.org/10.1111/jvp.13499 

Bottom line — The dosing regime could be challenging.

Acupuncture and Arthritis

The text explains that osteoarthritis (OA) is a degenerative joint disease affecting millions worldwide and causing significant pain, disability, and reduced quality of life. Traditional treatments such as exercise, weight loss, and pharmacologic pain management with agents like NSAIDs provide symptomatic relief but do not halt the progression of the disease and may cause serious side effects. This has led both human and veterinary patients to seek alternative treatments like acupuncture, which is believed to offer pain relief with fewer adverse effects. 

Acupuncture, a traditional Chinese medicine practice, involves the insertion of fine needles at specific points on the body and can be administered as manual acupuncture or electroacupuncture. Although numerous studies have reported that acupuncture can alleviate OA pain and inflammation, there are methodological inconsistencies, and the evidence is not yet strong enough to form a general clinical recommendation. Much of the previous research has focused on induced models of arthritis, which may not accurately reflect the natural, idiopathic form of OA seen in humans. 

The study discussed used the Dunkin-Hartley guinea pig model, which spontaneously develops knee OA in a way that resembles human pathology, to investigate the effects of manual acupuncture. Unlike previous studies that compared acupuncture to untreated controls, this study compared manual acupuncture with two comparator techniques—off-point acupuncture and needle sheath taps. Although manual acupuncture did not produce significant improvements in mobility or activity parameters, it did lead to a trend toward improved knee joint structure and significant reductions in markers of systemic inflammation such as Complement Component 3 and Prostaglandin E2. 

Gene expression analyses further revealed that manual acupuncture upregulated antiapoptotic and antioxidant genes at the acupoint and in the knee joint tissues, while decreasing proapoptotic transcripts and markers associated with cartilage degradation. An increase in nerve growth factor (NGF) immunostaining in the deep layers of articular cartilage was also observed in the manual acupuncture group, suggesting a potential regenerative effect in cartilage repair that was not seen with the comparator treatments. The study notes that differences in treatment frequency, timing of intervention, and the use of anesthesia might have influenced the outcomes and that manual acupuncture might have been more effective if initiated earlier in the disease process. 

In conclusion, while manual acupuncture did not significantly alter activity-based symptoms in the guinea pig model of OA, it appeared to favorably modify inflammatory markers and gene expression related to cartilage protection and regeneration. These findings support the potential of targeted manual acupuncture as a therapeutic approach, warranting further investigation into its long-term effects and optimal treatment protocols for OA. 

Spittler, A. P., Bukovec, K. E., Afzali, M. F., Leavell, S. E., Bork, S. B., Seebart, C. A., Santangelo, K. S., & Story, M. R. (2025). Short-term manual acupuncture decreased markers of systemic inflammation and altered articular cartilage transcripts in the Dunkin-Hartley model of osteoarthritis. American Journal of Veterinary Research https://doi.org/10.2460/ajvr.24.11.0341 

Bottom line — Another study measuring acupuncture effectiveness

Just putting things in perspective …