This case highlights the effectiveness of cannabinoid therapy in managing chronic and refractory pain, particularly in a patient unresponsive to opioids, NSAIDs, and corticosteroids. Rescue doses of both cannabis oil and morphine were required only four times over the 10-month treatment period, reflecting the stability achieved through the primary cannabinoid protocol. Improvements included a progressive increase in body condition score (Figure 1), weight gain, and enhanced coat quality, indicative of improved systemic health. Topical application to the wound demonstrated strong local anti-inflammatory effects and effective control of exuberant granulation tissue. Importantly, a significant decrease in pruritus was observed, leading to complete cessation of self-mutilation within 1 week of initiating treatment. These clinical improvements contributed to a progressive enhancement in the patient’s overall quality of life, and throughout the treatment course, no adverse effects were reported during standard dosing.

Despite the benefits, cannabinoid therapy showed no observable effect on the progression of late diagnosed osteomyelitis. In the final 30 days of life, the infection proved unresponsive to antibiotic therapy, and the pain became refractory, even when managed with high doses of THC and CBD in combination with morphine. At these escalated doses, the patient developed transient adverse effects, including ataxia, sedation, and drowsiness, though without signs of systemic toxicity. Ultimately, the osteomyelitic condition deteriorated, contributing significantly to the decision for humane euthanasia.

Pain management and regulation of inflammatory response remain challenging in equine medicine. Non-Steroidal Anti-Inflammatory Drugs (NSAIDs), such as phenylbutazone have a narrow margin of safety with severe side effects associated with excessive or prolonged usage in horses including gastroduodenal ulceration, right dorsal colitis (RDC) and renal papillary necrosis (43, 44). The use of this class of drugs is common in equine practice for orthopedic disease, laminitis, colic and neurological conditions (45–49).

Cannabidiol (CBD), a non-psychoactive phytocannabinoid derived from Cannabis sativa, has shown promising results in equine medicine. The dose range for cannabidiol for use in horses requires further study, with a wide range of dosages from 0.07 to 2 mg/kg orally per day having shown positive results. In-vitro studies demonstrated that CBD at 4 μg/mL reduced the production of inflammatory cytokines (TNF-α and IFN-γ) in peripheral blood mononuclear cells from senior horses (19).

Additionally, an in-vivo study using CBD oil solution given at 2 mg/kg orally for 90 days to senior horses significantly decreased inflammatory cytokine expression of IFN-γ in whole blood at day 60, and IL-6 at day 60 and 90 in CBD- treated horses, when compared to controls (placebo-treated/ 15 mL of soy) (18). Aragona et al. (21) showed that a combination of cannabinoids at a dose of 0.07 mg/kg qd every 24 h for 2 weeks was efficacious in lowering the levels of pain in horses with OA. Cannabidiol has also been reported to be effective in treating equine mechanical allodynia (20) and stereotypic behavior (29). Oral administration of cannabinoids appears to be well tolerated by horses in a wide range of doses (21, 50–53).

For the authors knowledge, there is no recent clinical study of the medical use of oral THC in horses. This case puts in evidence the clinical benefit of oral THC rich compound solution for horses and its safety in a long-term scalation dose protocol. The undesirable effects present were possibly related to THC rather than CBD administration (2 mg/kg THC + 4 mg/kg CBD). The clinical signs were ataxia, sedation, sleepiness and reduction of gut motility; not related to toxicity or shock. The presents find aligns with studies using compounds with THC in other species (54–57).

The role of cannabinoids in wound healing is an emerging area of investigation. These compounds are known to modulate inflammatory cell infiltration (58) and cellular proliferation (59, 60) —key processes involved in both physiological and pathological wound repair. In humans and mice fibroblasts specifically, CBD has been shown to influence the activity of matrix metalloproteinases (MMPs) (61–63), enzymes critical for extracellular matrix turnover. This is particularly relevant in the context of equine sarcoids, where MMPs are implicated in tumor progression, local invasiveness, and potential malignancy (64–66).

It is hypothesized that cannabinoids may exert dual therapeutic action on the wound site: not only by promoting wound healing through anti-inflammatory, proliferative, and apoptotic mechanisms, but also by downregulating MMP activity, thus potentially inhibiting sarcoid progression. In other tumor models, such as human breast cancer (38, 67), cannabinoids have demonstrated the ability to induce cancer cell apoptosis and interfere with aromatase expression, further supporting their antineoplastic potential (38, 68). A recent paper evaluated the response of equine sarcoid cells to CBD in vitro, focusing on viability, invasiveness, and matrix remodeling (69). Treatment with CBD affected cell viability, cytotoxicity, and apoptosis. At 48 h, apoptosis (measured as caspase 3/7 activity) reached 49.5% and further increased to 75% at 72 h. Marked cytotoxicity (>96%) and decreased viability were observed at 72 h. Cannabidiol also significantly decreased MMP-1 concentration by 48.9% at 24 h and MMP-2 concentration after 6 h (69).

In this case, the combined anti-inflammatory and citomodulatory properties of the full-spectrum cannabinoid therapy appear to have contributed to effective granulation tissue control, enhanced re-epithelialization, and stable wound healing, all without evidence of neoplastic growth. Although cannabinoids modulate key processes involved in wound repair—such as inflammation (70), fibroblast proliferation (69), and matrix metalloproteinase (MMP) activity (69)—the relatively long period required to observe clinical resolution in the present case (approximately 8 months) may also be related to the pharmaceutical formulation used. The cannabinoids were administered in a conventional oil-based formulation without the use of advanced drug-delivery technologies. Oral oil preparations of lipophilic molecules such as cannabinoids are known to present variable gastrointestinal absorption and relatively low bioavailability due to extensive first-pass hepatic metabolism (30, 71, 72), which may reduce the proportion of the active compound reaching systemic circulation and target tissues. Consequently, sustained administration over extended periods may be required before clinically significant effects become evident.

Similarly, although topical application was employed directly at the wound site, conventional oil-based preparations may also present limited transdermal penetration when compared with advanced delivery systems. The diffusion of cannabinoids through the skin barrier is influenced by multiple factors, including formulation characteristics, molecular solubility, and carrier systems (73). Advanced pharmaceutical technologies such as nanoencapsulation or liposomal formulations have been developed to enhance drug penetration across biological membranes and improve tissue targeting (74). These systems can increase local absorption, improve bioavailability, and reduce metabolic degradation, thereby enhancing therapeutic exposure at the target site (74–77). In human medicine, particularly in oncology, liposomal and nanoparticle-based delivery platforms are widely used to optimize the delivery and efficacy of chemotherapeutic agents (67, 78). Emerging evidence suggests that similar strategies may also enhance the therapeutic potential of cannabinoids (79–81).

Regarding appetite stimulation, this effect is well established in human clinical trials. In patients with systemic sclerosis associated with anorexia and malnutrition, treatment with THC and CBD in a 1:1 ratio resulted in improvements in appetite, satisfaction with eating, ability to eat more, body weight and daily calorie intake (82). In addition, THC has been widely used in oncologic patients and, beyond its orexigenic effects, has demonstrated an ability to attenuate weight loss in individuals with advanced malignant tumors (83). There is a possible involvement of CB1 receptors located in the hypothalamus, where food intake is regulated, as well as the mesolimbic reward system, which plays a role in the motivation and reward aspects of feeding (84). There is a lack of information regarding appetite stimulation in horses. Cunha et al. (29) described an increase in appetite 1 hour after isolated CBD administration for the treatment of crib-biting. After 1 week of treatment, the horse showed a sustained enhancement of appetite, and by the end of 30 days, an improvement in body condition score (BCS) was observed.

In this case, several practical limitations and inherent risks must be acknowledged. The range of therapeutic and procedural options was constrained by a combination of financial limitations on the part of the owners and the geographical location of the case, which affected the availability of advanced veterinary interventions. In an ideal scenario, the patient would have benefited from surgical debridement, extensive wound flushing, surgical antibiotic protocols, and possibly the placement of drainage systems to manage the infection more aggressively. Another limitation of this study is the absence of a validated and standardized pain scoring system. Pain assessment was performed daily by the veterinary team through clinical observation of behavioral and physiological parameters consistent with the equine pain ethogram (42) and known pain-related behaviors (85). However, because the evaluation relied on qualitative clinical judgment rather than an validated composite pain scale, a degree of subjectivity cannot be excluded and comparisons with studies using standardized pain assessment tools may be limited.

Although the histopathological diagnosis was consistent with an equine fibroblastic sarcoid, it should be acknowledged that in extensive and highly reactive lesions such as the one described in this case, histopathological differentiation between exuberant granulation tissue and sarcoid tissue can be challenging and is not always definitive (86). In severe chronic wounds, marked inflammation, fibrosis, and reactive tissue proliferation may obscure classical histological features, potentially limiting diagnostic accuracy (87). Additionally, although copper sulfate was applied locally during wound management, the authors recognize that this approach is not recommended in contemporary equine wound care due to its potential to cause tissue irritation and delayed healing (88, 89). Its use in this case highlights the practical challenges frequently encountered in long-term cases, where owner-driven treatments and variable compliance with veterinary recommendations may influence wound management strategies.

The necessity to rely on a palliative, multimodal approach—involving cannabinoids alongside other analgesics—was in part due to these constraints. While this approach succeeded in improving quality of life significantly, it is important to recognize that the outcome of euthanasia reflects the severity of the underlying condition and the challenges inherent in managing advanced neoplastic and infectious processes in a resource-limited setting. In discussing the limitations and risks of this case, it is important to emphasize that this is a single clinical case report. The patient required intermittent doubling of the cannabinoid dose and the addition of morphine during certain acute phases, highlighting the severity of the pain and the clinical challenge of managing such a complex case. This underscores the necessity of a multimodal approach, integrating multiple therapeutic agents to achieve palliation.

From the authors’ perspective and clinical experience with prescribing cannabinoids in horses, both THC and CBD may represent a potential shift in how equine veterinarians manage pain and, consequently, the patient. With the use of cannabinoids, pain appears to be markedly attenuated, within the limits imposed by dosage and safety considerations. While this represents a positive step toward improving comfort and appropriately addressing pain in equine patients, it may also introduce a clinical challenge: the need for substantially intensified follow-up and monitoring. When pain is effectively managed, certain clinical signs may be masked or reduced, potentially delaying the recognition of disease progression or complications. As a result, closer and more frequent clinical evaluations become essential. This consideration does not disqualify cannabinoids as a therapeutic tool; on the contrary, their use may significantly enhance comfort and overall well-being in suffering equine patients, provided that adequate clinical surveillance is maintained.

It is also crucial to note that although the outcome was euthanasia, the primary goal of palliative care was achieved, as the patient’s quality of life significantly improved during the treatment period. The use of full-spectrum oils containing 100 mg/mL of both THC and CBD, along with other cannabinoids, likely contributed to the safety and therapeutic balance of the protocol. The entourage effect of full-spectrum cannabis may enhance analgesic and anti-inflammatory benefits while minimizing adverse effects within a therapeutic window (90, 91).

Following treatment initiation, the owner observed visible improvement in wound appearance, reduced exudate, and healthier tissue margins, accompanied by decreased discomfort and distress. Ongoing communication with the veterinary team, supported by regular photographic and video updates, guided therapeutic adjustments and reinforced collaborative decision-making. The owner identified the cannabis-based therapy as the first intervention to provide sustained clinical improvement and stability, reporting a meaningful enhancement in the horse’s quality of life despite eventual disease progression and euthanasia.