Some veterinary cases are difficult because the diagnosis is unclear. Others are difficult because the diagnosis is clear, but the patient keeps coming back. The dog with chronic inflammatory skin disease improves, then flares again. The cat with persistent gastrointestinal signs responds partially to dietary and medical management but never quite reaches the quality of life the veterinarian and owner hoped for. A senior dog has several chronic inflammatory or painful problems, but the therapeutic plan is becoming increasingly complicated.

And sometimes the veterinarian has already addressed the obvious questions: Is the diagnosis right? Are secondary infections controlled? Is the diet appropriate? Is the owner actually able to give the medication? Are established therapies being used appropriately? Yet there is still room for improvement. Those are often the patients who push veterinarians to look beyond the most familiar treatment toolbox.

One medication beginning to generate interest is low-dose naltrexone or LDN. Many integrative human-medicine prescribers are already familiar with it. Veterinarians may be less so.

Naltrexone itself is not new. It is an opioid-receptor antagonist with decades of pharmacologic history. What is different is the use of substantially smaller doses with the goal of influencing endogenous opioid and inflammatory signaling rather than simply producing sustained opioid blockade. Interest in veterinary LDN has grown enough that a 2024 veterinary review specifically examined potential uses in dogs and cats, including inflammatory, dermatologic, gastrointestinal, pain, and other conditions. More recently, published veterinary literature has begun to include actual companion-animal LDN cases. That does not mean LDN is an established therapy for canine atopic dermatitis, feline inflammatory disease, or chronic enteropathy. It means something more interesting: Veterinary LDN has moved from a largely theoretical conversation toward an emerging clinical one and it is worth understanding before your next client asks you about it.

What Makes Low-Dose Naltrexone Different From Naltrexone?

This distinction is fundamental. Naltrexone is traditionally used because it blocks opioid receptors. At lower doses, however, the pharmacologic goal is different. LDN is proposed to cause a shorter period of opioid-receptor antagonism that may alter endogenous opioid production and receptor signaling afterward. Interest also extends beyond the classic opioid receptors. Experimental literature has examined effects on neuroimmune signaling, including Toll-like receptor 4 pathways and downstream inflammatory mediators. Another area of interest involves the opioid growth factor receptor system, which has been studied in relation to cell proliferation, tissue repair, inflammation, and immune signaling.

As with human LDN, these mechanisms are attractive because they offer a biologic explanation for why a drug best known as an opioid antagonist could potentially influence inflammatory or pain-related conditions. But mechanism should not be confused with clinical proof.

The useful takeaway is not: “LDN stimulates endorphins, therefore it treats autoimmune disease.”

It is: “There are biologically plausible mechanisms that have generated enough positive experimental and human data to justify studying whether those effects translate into meaningful veterinary outcomes.” That is where veterinary medicine currently sits.

The Veterinary Evidence Is Early but It Is No Longer Zero

One of the challenges in discussing veterinary LDN is that the evidence is often described in extremes. One side may suggest LDN works for a remarkably broad list of canine and feline diseases. The other may dismiss the therapy because randomized veterinary trials do not yet exist for most of those indications. Neither description is particularly useful. The more accurate characterization is: Direct companion-animal evidence remains early, but several different lines of evidence make continued veterinary investigation reasonable. Those lines include:

• Decades-old veterinary research showing that naltrexone can influence licking, scratching, and other opioid-linked behaviors in dogs
• Experimental animal research demonstrating effects on inflammatory pathways and colitis
• A growing human LDN literature involving inflammatory, dermatologic, pain, and gastrointestinal disorders
• A 2024 veterinary review proposing potential applications in dogs and cats based on those pharmacologic properties
• Newer companion-animal reports evaluating oral LDN directly

In 2026, for example, a small veterinary oncology case series evaluated compounded oral LDN as part of palliative care in dogs with several cancers. Only four dogs were ultimately evaluable, so the study certainly does not establish efficacy. But owners reported maintained or improved quality-of-life measures across domains such as appetite, mobility, comfort, hydration, and mental status, and no adverse events were reported. The importance of that report is not that LDN should now become an oncology standard. It is that published veterinary LDN use is beginning to move from extrapolation into direct clinical observation. That is an important step in the development of any emerging therapy.

Dermatology: An Old Veterinary Signal That Is Easy to Miss

Interestingly, the connection between naltrexone and veterinary dermatology is not entirely new. Researchers were studying opioid antagonists in dogs with chronic licking and scratching behavior more than three decades ago. In one study, 11 dogs with refractory self-licking, self-chewing, or scratching associated with various irritative or pruritic disorders were treated with opioid antagonists. Naltrexone was administered to some of those dogs at 1 mg/kg subcutaneously. Seven of the 11 dogs had a significant reduction in the unwanted behavior, three had a partial response, and one did not respond. Dogs with acral lick dermatitis showed the strongest response.

A subsequent study specifically evaluated 11 dogs with acral lick dermatitis treated with naltrexone. Seven achieved cessation of licking with re-epithelialization of the lesion. When naltrexone was stopped, the lesions recurred in all seven responders; when the drug was restarted, five again re-epithelialized. That is a fascinating veterinary signal. But it is important to understand what it does—and does not—tell us. These were naltrexone studies, not modern LDN trials, and acral lick dermatitis is not equivalent to canine atopic dermatitis. The dose and therapeutic rationale were different. So we should not take an old lick-granuloma study and conclude: “LDN treats canine allergies.” But it does tell us something valuable. The opioid system appears capable of influencing veterinary itch, licking, scratching, and repetitive behaviors. That biologic connection is consistent with human dermatology literature in which opioid-pathway modulation, including naltrexone, has demonstrated antipruritic effects in several conditions. It gives veterinarians a legitimate reason to remain interested in what lower-dose opioid modulation might eventually offer for difficult inflammatory and pruritic patients.

What About Atopic Dermatitis?

This is where precision becomes especially important. A 2024 veterinary review specifically identified atopic and allergic dermatitis among proposed areas of potential LDN use in dogs and cats. But that review is primarily a pharmacologic and translational argument. It does not provide the type of controlled canine atopic dermatitis trial that would allow us to say LDN has demonstrated efficacy comparable to established dermatologic treatments. For a veterinarian, that means LDN should not jump ahead of appropriate workup and proven therapy. A dog with allergic skin disease still needs the fundamentals handled well:

• Parasite control
• Identification and treatment of secondary infection
• Appropriate consideration of food allergy
• Control of pruritus and inflammation
• Skin-barrier support
• Long-term management of the underlying allergic disease when indicated

LDN does not make any of those steps unnecessary. Where the conversation becomes interesting is the patient for whom those steps have already been considered and the veterinarian is looking for an adjunct, not a replacement. Consider the chronic allergic dog who is meaningfully improved on an established plan but remains difficult to control. The reasonable question is not: “Should I stop Apoquel or Cytopoint and use LDN instead?” The veterinary evidence does not support that conclusion. The more useful question is: “Could modulation of the opioid and inflammatory pathways eventually offer another adjunctive tool for selected chronic pruritic patients and is this a patient in whom an evidence-aware therapeutic trial is reasonable?” That is the appropriate level of enthusiasm today.

Gastrointestinal Disease: An Interesting Translational Story

The gastrointestinal rationale follows a somewhat different path. There are not currently robust controlled trials showing that LDN treats naturally occurring canine or feline chronic enteropathy. That needs to be said plainly. But the translational story is interesting. In an experimental mouse model of inflammatory bowel disease, naltrexone treatment in moderate colitis reduced weight loss, disease-activity scores, histologic evidence of inflammation, and expression of pro-inflammatory cytokines including IL-6 and IL-12. Importantly, the same study found that more severe colitis did not respond significantly. That is a useful finding because it is not uniformly positive. It suggests that the relationship between opioid signaling and intestinal inflammation may depend on disease state and severity rather than behaving like a universal anti-inflammatory switch.

Other experimental work has continued to investigate opioid receptors and naltrexone in murine colitis models. And, as discussed in our human GI review, early clinical research in people with Crohn’s disease has produced encouraging clinical and endoscopic signals. Together, those findings provide a translational rationale for veterinary interest in chronic inflammatory GI disease. But translation has several steps: Mouse model → human IBD → naturally occurring disease in dogs and cats. Those steps cannot simply be skipped. So for the neighborhood veterinarian treating chronic enteropathy, LDN belongs in the category of “Interesting emerging adjunct worth following and potentially discussing in selected cases,” rather than “Evidence-based standard treatment for canine or feline IBD.” That distinction protects both scientific credibility and the patient.

A Practical Example: The Dog With Chronic Enteropathy Who Is Better, but Still Struggling

Imagine a dog with chronic enteropathy. The veterinarian has appropriately investigated the patient. Diet has been addressed. Parasites and other differentials have been considered. Established treatment has improved the clinical picture. But the owner still reports intermittent GI signs, inconsistent appetite, or quality-of-life issues. This is exactly the kind of situation where emerging therapies can become tempting. The wrong question is: “Can I replace the current treatment with LDN?” There is not companion-animal evidence to support that approach. A more reasonable question is: “If the current plan is appropriate but incomplete, could LDN be considered as a carefully monitored adjunct after I discuss the emerging nature of the evidence with the owner?” If the veterinarian decides the answer may be yes, the next step is not simply writing “LDN” on the prescription. The therapeutic trial should have a purpose. What specifically are we hoping to change?

• Appetite?
• Stool consistency?
• Frequency of vomiting?
• Abdominal discomfort?
• Body weight?
• Activity?
• A validated chronic-enteropathy activity score?
• Ability to reduce another medication eventually?

That leads to one of the most important principles in emerging therapy: If you cannot define what improvement would look like, you cannot reliably determine whether the treatment worked.

Clinical Pearl #1: “Emerging” Should Change How You Monitor—Not Automatically Stop You From Trying

Veterinary medicine routinely uses therapies where the evidence is less complete than anyone would ideally like. The question is how the uncertainty is handled. With an established therapy, the veterinarian generally has clearer expectations regarding dosing, efficacy, adverse effects, and monitoring. With an emerging therapy such as LDN, uncertainty should lead to more deliberate evaluation. Before starting, identify:

• Why the therapy is being considered
• Which outcome is being targeted
• What other medications are being continued
• When the patient will be reassessed
• What would justify continuing
• What would justify discontinuing

That transforms “Let’s try LDN and see what happens.” into “Let’s conduct a patient-specific therapeutic trial.” That is a far more useful way to approach emerging medicine.

Clinical Pearl #2: Don’t Confuse Naltrexone Data With LDN Data

This is particularly important in veterinary medicine. Some of the most interesting canine naltrexone studies, including the acral lick dermatitis work, used doses and administration methods that would not necessarily fit a modern definition of LDN. Those studies remain valuable. They demonstrate that opioid antagonism can influence clinically relevant behavior and pruritus in dogs. But they do not establish the correct low-dose regimen for canine allergic skin disease. Likewise, human LDN studies cannot simply be converted into dog or cat dosing by copying a 4.5 mg prescription. Species matter. Weight matters. Pharmacokinetics matter. The indication matters. And the veterinary dose-response relationship for many proposed LDN uses has simply not been established yet. The best way to use older naltrexone and human LDN literature is to generate clinical hypotheses, not false precision.

Clinical Pearl #3: Ask About Opioids—Especially Before Surgery or Pain Treatment

Naltrexone is an opioid antagonist. That fact does not disappear because the dose is low. If a dog or cat is receiving (or is likely to require) opioid analgesia, the veterinarian needs to know that naltrexone is part of the medication plan. That may include medications such as:

• Buprenorphine
• Hydromorphone
• Morphine
• Fentanyl
• Methadone
• Butorphanol
• Other opioid-based analgesic protocols

This becomes especially important around procedures, trauma, surgery, or palliative care. A veterinarian considering LDN should therefore think ahead: “If this animal suddenly needs opioid analgesia, will everyone treating the patient know that naltrexone has been prescribed?” Medication reconciliation matters just as much in veterinary medicine as it does in human medicine. And because LDN use may originate from an integrative practitioner, specialist, or outside pharmacy, it may not always be obvious on first review.

Clinical Pearl #4: Don’t Let the Internet Choose the Dose

Human LDN has developed a recognizable dosing culture. Owners searching online may encounter statements such as “Everyone eventually goes to 4.5 mg.” That is not a veterinary dosing principle. Even in human medicine, 4.5 mg is not a universal biologic target. And in dogs and cats, the evidence supporting indication-specific dosing is substantially less developed. Interestingly, the Merck Veterinary Manual now mentions low-dose naltrexone at 0.02 mg/kg orally every 24 hours among possible additional options for dogs with severe osteoarthritis—but explicitly notes that this recommendation is based on human data and that animal data are limited. That is a useful example of where veterinary LDN currently stands. The concept is entering veterinary clinical references. The dose is being discussed. But the evidence is still being identified as limited. For dermatologic and GI conditions, the goal should therefore not be to reproduce a human LDN protocol automatically. Dose selection should reflect the animal, the indication, available evidence, clinical experience, and the veterinarian’s therapeutic objective.

Clinical Pearl #5: Look for the Benefit That Matters to the Owner

Veterinary patients cannot tell us, “My inflammatory symptoms are 30% better.” Much of our assessment comes from observable function and owner reporting. That makes defining outcomes especially important. For a dermatology patient, useful measures might include:

• Frequency of scratching
• Time spent licking
• Sleep interruption
• Visible lesion severity
• Frequency of secondary infection
• Need for rescue therapy

For a GI patient:

• Vomiting frequency
• Stool quality
• Appetite
• Body weight
• Activity
• Abdominal discomfort
• Frequency of flares

The recent veterinary oncology LDN case series used a structured quality-of-life questionnaire rather than simply asking owners whether they thought the medication “worked.” That approach is worth borrowing even outside oncology. If LDN is being tried because quality of life is the goal, measure quality of life as deliberately as practical. The owner should know what changes to look for before the first dose is ever given.

Where Compounding Actually Adds Value

LDN creates an obvious compounding problem. Commercial naltrexone products were not designed around veterinary low-dose use. And veterinary patients present an additional layer of complexity: A six-pound cat and an 80-pound Labrador are not the same patient. Compounding can allow the veterinarian to prescribe:

• Patient-specific low-dose strengths
• Small capsules appropriate for the animal
• Flavored liquids when capsules are not practical
• Concentrations that minimize administration volume
• Incremental strengths when titration is desired
• Formulations that avoid unnecessary ingredients when clinically relevant
• A practical dispensing system that makes small doses easier for an owner to administer accurately

In an emerging therapy, dose accuracy matters even more. If the veterinarian is attempting to learn whether a very small dose produces a meaningful response, an imprecise dosage form makes the therapeutic trial harder to interpret. That is where individualized formulation becomes part of the clinical experiment.

What a Good Veterinary Compounding Pharmacy Should Actually Solve

The veterinarian should not have to become an LDN formulation expert before considering the medication. You may have questions such as:

• What strengths can actually be prepared accurately for this animal?
• Is a capsule or liquid more practical?
• How small can the administration volume reasonably be?
• Can the dose be titrated without creating a confusing schedule for the owner?
• Are there formulation limitations I should know about?
• Is the medication compatible with the other drugs the animal is receiving?
• What should I tell the owner about administration?
• Is there enough evidence for this indication to make the conversation reasonable in the first place?

Those are exactly the kinds of questions a collaborative pharmacy should help you work through. You can call Custom Care without already knowing the answer. Bring us the patient, the clinical objective, and the problem you are trying to solve. For example: “I have a chronic inflammatory patient who is improved but still symptomatic, and I’m curious whether LDN is reasonable as an adjunct.” “I want to explore LDN, but this is a very small cat and I need a practical dosage form.” “An owner asked me about LDN and I want to know what veterinary evidence actually exists before I decide whether to use it.” The useful pharmacy relationship is not one in which every question automatically produces a compounded prescription. It is one where the veterinarian has another resource to help evaluate whether the idea is reasonable and, if it is, make it practical.

The Bigger Opportunity With Veterinary LDN

Veterinary LDN is not where human LDN is today. That is important to acknowledge. The direct dog-and-cat evidence is still emerging. There are intriguing older canine naltrexone studies, experimental inflammatory findings, a rapidly growing human literature, veterinary literature explicitly discussing potential LDN applications, and new published companion-animal cases. Even mainstream veterinary references have begun mentioning LDN in selected contexts while clearly acknowledging that the animal evidence remains limited. That is not proof. But it is also not nothing. It is how many interesting therapeutic ideas begin.

The appropriate response is not “There isn’t a large canine randomized trial, so ignore it.” And it is not “The human data look good, so LDN must work in dogs and cats too.” There is a much better middle ground: Follow the evidence. Understand where it came from. Be clear about what has and has not been demonstrated in the target species. Choose the patient carefully. Define the goal. Use an accurate dose. Monitor the response. That allows veterinarians to remain open to innovation without lowering their evidentiary standards. And as more veterinary research emerges, the role of LDN may become much clearer. For now, it belongs where many useful veterinary tools began: as an emerging option worth understanding and, in thoughtfully selected patients, worth discussing.

For Pet Owners: Heard About LDN for Dogs or Cats?

You may have encountered low-dose naltrexone through a friend, an online pet group, or information about its use in people. Veterinary interest in LDN is growing, but research in dogs and cats is still developing and the amount of evidence differs by condition. That means LDN should not replace a proper veterinary diagnosis or established treatment simply because it sounds promising. A better first step is to ask your veterinarian: What are we trying to improve? What treatments have already been considered? Is LDN reasonable as an additional option for this particular pet? And how would we know whether it is actually helping? If your veterinarian decides LDN is appropriate, Custom Care can prepare patient-specific low-dose formulations and work with the veterinary team to make the prescribed dose practical for your pet.

Have a Patient Who Makes You Curious About LDN?

You do not need to be an LDN expert before contacting us. If you have a difficult chronic inflammatory, pruritic, painful, or gastrointestinal patient and are wondering whether LDN deserves consideration, bring us the clinical question. Our pharmacy team can help you review formulation possibilities, discuss practical patient-specific dosing options, and identify some of the evidence behind the conversation. Sometimes the answer may be “The veterinary evidence isn’t strong enough for me to use this here.” Other times it may be “This is emerging, but given this patient’s situation, I think a carefully monitored adjunctive trial is reasonable.” Both are good clinical decisions. The important thing is having enough information—and enough tools—to make them deliberately.

Selected Clinical References

• Marangaloo RG, Pinar O, Mehmedov T, Or ME. Current Pharmacotherapeutic Properties of Low-Dose Naltrexone Therapy in Humans and Possible Therapeutic and Prophylactic Indications in Cats and Dogs. German Journal of Veterinary Research. 2024.
• Dodman NH, Shuster L, White SD, et al. Use of Narcotic Antagonists to Modify Stereotypic Self-Licking, Self-Chewing, and Scratching Behavior in Dogs. Journal of the American Veterinary Medical Association. 1988.
• White SD. Naltrexone for Treatment of Acral Lick Dermatitis in Dogs. Journal of the American Veterinary Medical Association. 1990.
• Garza MA, Hoffart S, Parsons-Doherty M, et al. Case Series of Veterinary Cancer Patients Treated With Oral Low-Dose Naltrexone. International Journal of Pharmaceutical Compounding. 2026.
• Smith JP, Bingaman SI, Ruggiero F, et al. The Opioid Antagonist Naltrexone Improves Murine Inflammatory Bowel Disease.
• Toljan K, Vrooman B. Low-Dose Naltrexone (LDN)—Review of Therapeutic Utilization. Medical Sciences. 2018.
• Gouda AHK, Aitcheson NEC, Steadman KJ. Low-Dose Naltrexone: What Is the Evidence? A Narrative Review.Advances in Therapy. 2026.
• Merck Veterinary Manual. Osteoarthritis in Dogs and Cats. Used here to contextualize emerging veterinary mention of LDN and the limited nature of animal data.