Could Medical Marijuana Or CBD Oil Help My Dog Or Cat?

Cannabis, Cannabinoids, CBD Oil, THC, And Synthetic Products

Ron Hines DVM PhD

  Pain Control In Your Cat 

  Dealing With Arthritis In Your Dog  

   Caring For Your Elderly Cat  


   Solensia® A New Approach To Arthritis Pain In Cats

   Librela® A New Approach To Arthritis Pain In Dogs

The short answer is no. What you can legally purchase is probably harmless. But it is highly unlikely to be of any help to your dog or to your cat. RSH

When pet owners ask me for advice, one of the most common problem they are struggling with in their elderly pets is arthritis. They worry that it’s getting harder and harder for their pet to get around as well as it once did.  

 Your Options

 When veterinarians are consulted and your pet is a dog, they often dispense or suggest an NSAID.  But NSAIDs like carprofen (Rimadyl®, etc.) occasionally produce serious stomach and intestinal side effects. Recently, that potential side effect was examined for six NSAIDs that veterinarians commonly dispense, carprofen (e.g. Rimadyl®), meloxicam (e.g. Metacam®), firocoxib (Previcox®), deracoxib (Deramaxx®) or piroxicam. Of those six, carprofen and meloxicam appear to be the safest. (read hereUnfortunately that study did not include grapiprant (Galliprant®). None of these medications, when given at effectively high doses, are safe for cats. 

Medications such as tramadol are sometimes less effective than one could hope for (3.8 pain relief versus 10 for a fentanyl patch). Veterinarians shy away from dispensing fentanyl patches  (e.g. Duragesic®), a much more effective pain-relieving medication, because of constipation issues and the fear of the DEA

Corticosteroids do reduce arthritis pain. Veterinarians dispense them for you to gain a little more time with a fading pet, to treat autoimmune diseases and as a last resort to improve appetite and well-being in situations such as untreatable cancer or FIP in cats, etc. However, corticosteroids bring their own long list of serious side effects.  Corticosteroids, when combined with NSAIDs, make intestinal bleeding even more likely. (read hereThose are some of the reasons that many of the emails I received ask me what I think about giving their pet marijuana or CBD oil to relieve its chronic pain. 

Is There Increased Interest In Giving Medical Marijuana To Dogs And Cats?

Yes. Relaxation of the laws prohibiting the use of cannabis, its active ingredients or synthetic derivatives in humans is the inspiration for increased pet owner, commercial and veterinary interest in those products. Pets have become family members. People naturally began to think: “If there are legitimate medical uses for marijuana for my human family and myself, why not for my furry family members as well?” Veterinarians are not immune to that line of thinking either, and they are being asked that question more and more by the owners of the dogs and the cats that they treat.

Do These Cannabis Oil Products I See For Sale Actually Work? 

 Probably not.  Particularly when they contain little or no tetrahydrocannabinol (THC). (read here

Building a knowledge base for the safe and effective use of cannabis/marijuana products in dogs and cats presents many challenges. For one, your pet can’t tell you if it’s working. Only an activity monitor might do that. Besides, so many other factors influence the perception of pain. Your pet is exquisitely sensitive to your mood and thoughts. If you are optimistic that a drug will help, your pet is likely to be too. 

The second problem is the lack of legitimate scientific studies such as the ones that rely on activity monitors. It’s generally testimonials designed and disseminated by people with cannabis products they want you to buy. My veterinary journals are full of those ads urging veterinarians to stock their products.

The kind of experiments that are required to determine a safe and effective dose for pain control in pets would be quite difficult to perform now in the United States, the UK or Europe because of heightened public sensitivity to humane issues. At one time, gruesome techniques were used to measure the effectiveness of medications to alleviate pain (such as timing how long it took a rat to get off a hotplate). The only semi-scientific “study” that found cannabidiol oil to be effective in relieving arthritis pain in dogs was paid for by the company marketing that product to veterinarians. (read here) Their findings were entirely subjective, free of the scientific method. No mention was made of the desirability of using the best pain-judging method, activity monitors, to see if the pet’s pain was actually lessened. (read here,   here  &  here) Because of those issues, using cannabinoids in dogs and cats today is manufacturer-driven, relying on word of mouth, subjective opinions and assuming that dogs and cats will react to these medications in the same way that we humans do. Physicians face this same dilemma and uncertainty. (read here,   herehere

Your Pet’s Natural Cannabis (Endocannabinoid) System

Real marijuana (cannabis) does what it does because it mimics (copies) natural messenger compounds in your body and in your pet’s body that have a similar functions. It just delivers those messages louder, stronger and for a much longer period of time. Your pet’s natural messenger cannabinoids are anandamide and (2-AG). They stimulate receptors present in your pet’s brain (CB1 receptors) and throughout its body (CB2 receptors). The cannabinoids in marijuana attach to those same receptors. However, they resist letting go of those receptors, so their effect is more powerful and longer lasting. Drugs that hang on to receptors longer than the natural messengers are called an agonist. The chief agonist cannabinoids in marijuana are Δ9-tetrahydrocannabinol (aka THC or delta-9) and cannabidiol  (aka CBD). The echinacea plant has a few similar compounds. When the effects of cannabinoids do wear off, it is because the compounds were processed (metabolized) by your pet’s liver into compounds that then left its body through bile and urine or moved to storage in an inactive state in your pet’s body fat. One of the effects of cannabinoid CB1 is to decrease neuropathic pain  (not arthritic pain).  Neuropathic pain is pain attributed to inflamed nerves rather than inflamed body tissue in general. What, if anything, cannabinoids or CBD oil do that affect the pain of arthritis, bone and joint inflammation is unknown. 

What Do Veterinarians Know About The Effects of Cannabis And CBD Oil On Pain?

We don’t know much. It is very difficult to objectively evaluate the intensity of pain in dogs and even more so in cats. They are so attune to us. Dogs and cat intuitively sense our optimism, our fear, our mood. The stroke of your hand, a calm optimistic voice, your body language, all make your pet feel better or worse. That makes it quite hard to decide what the effects really were of the medications you gave it. When it comes to dogs and cats and marijuana products, we have to rely on the feedback we get from people that take cannabinoids or CBD oil to deal with chronic pain and their other health issues. Most of these people do feel they experienced some benefit. But most describe the benefit as “modest”. When humans consume cannabinoids in an attempt to decrease arthritis pain, they describe the effects as being about the same as topical capsaicin liniments. (read here)  The pain-relieving benefits of a synthetic cannabinoid (nabilone) never approach that of the powerful narcotic opiate pain relievers such as hydrocodone or fentanyl patches nor do they match the pills dentists commonly prescribe for a toothache, codeine. (read here) However, it is hard to separate pain from mood and cannabis certainly makes people leave their worries behind them.  In one study, arthritic rats did seem to benefit from the (delta 9) THC that is present in marijuana. (read here) That study was small in size. But it was enough to get the NIAAA to fund human trials with standardized amounts of cannabinoids to see how they might affect osteoarthritis knee pain. These trials were halted due to an unacceptable number of heart and circulatory problems as well as undesirable changes in liver function in the patients who received the medications. (read here)


We all know that marijuana stimulates appetite in people. We could assume it has a similar effect in dogs and cats and might allows them to regain lost weight. But no veterinary studies regarding that have ever been done. What we have currently is folks telling us that the appetite of their sick pets improved on edible cannabis butter or liquid marijuana extract. With time, it might become more apparent if that is really true. Hope plays a big part in people’s perceptions, but hopes sometimes do come true.  You are more likely to find Entyce®,   Elura®  or Mirataz®(mirtazapine) effective. Valium® (diazepam) and Versed® (midazolamsometimes have the ability to stimulate a pet’s appetite too.  But they are tightly controlled by the DEA. For all five of them, there is considerably more positive appetite-stimulating data than there is for CBD oil. 

If My Dog Or Cat Eats Or Inhales Marijuana/Cannabis, What Would Be The Signs Of An Overdose?

Veterinarians know the signs of marijuana overdose in pets considerably better than they know the drug’s benefits to pets. When overdoses accidentally occur, 96% have been in dogs and only 3% in cats (perhaps because cats are less attracted to sweets).  It has been very rare for pets, consuming a single dose or any size, to die.

What veterinarians do see instead is usually a staggering dog (ataxic) with a slow heart rate and low blood pressure. Drooling and salivation are common.  Many are lethargic (sleepy) but with noise they may act startled. Many have dilated pupils (mydriasis). Some have abnormally low body temperatures (~98 F /36.7 C) and slow heart rates (~60 bpm). A few develop eye twitches (nystagmus). Some pets develop diarrhea and/or vomit. Those that do have often consumed multiple things (including stem fiber) that they found when their owners were not looking. Some loose bladder control, dribble urine or pee inappropriately.  Others develop muscle twitching or tremors.

In the most serious cases, pets come in fearful, anxious, disoriented or in a state of collapse. Anxiety seems worse in dogs that have a prior tendency to fearfulness and anxiety. You would expect that in a pet experiencing an altered mental state that it did not understand.  Those tense fearful pets are most likely to react in an exaggerated way to sudden movements or noises.

Because chocolate often formed part of what these pet consumed, it is hard to tell which signs are due to the stimulants in the cocoa (theobromine & caffeine) and which are due to the marijuana. (read here) Most cases of marijuana intoxication in pets due to a single ingestion incident resolve over a period of 3 – 12 hours with no lasting damage.

Test kits designed to detect marijuana in the urine of humans have been used to detect cannabis exposure in pets. But those tests miss some cases. The test only measures an end product of cannabis (11-nor-9-Carboxy-THC, aka 11-nor-9-carboxy-delta-9-tetrahydrocannabinol, 11-COOH-THC, THC-COOH) when it is found in the pet’s urine after a marijuana exposure.  These tests are of dubious value because it is known that dogs do not produce those same end products in the quantities that humans do. (read here)

How Might My Veterinarian Treat A Cannabis / Marijuana Overdose?

Once your veterinarian determines that your pet is not in immediate danger and is lucid (knows what’s going on and has normal body strength), he/she might induce your pet to vomit if the ingestion (eating it) was recent (with apomorphine) or give it an oral dose of activated charcoal if more time has passed. It is probably not a good idea to induce vomiting in a semi-conscious or mentally incapacitated dog. Even if marijuana was not high on the list of possible causes for your visit, it is often given because it is thought that this form of charcoal lessens the absorption of many toxic products. If more time had passed, a laxative (e.g. sorbitol) might be given to flush out the remaining contents of your pet’s digestive tract. If your pet’s blood pressure is low or if it has become dehydrated due to vomiting, diarrhea or the inability to drink, IV fluids might be suggested as well. Pets with subnormal temperature will get supplemental warmth – perhaps a hot water bottle or a controlled cage environment.

Depending on the severity, your pet might also get round-the-clock observation.  When symptoms are mild, all that might be required is a quiet environment without noise or other sensory stimuli such as barking dogs and strangers. Anxious dogs might even receive a mild antianxiety sedative such as diazepam to control tremors, agitation or seizures.  (read here) Veterinarians might try to avoid that because the signs of sedation are easily confused with the signs of cannabinoid toxicity. But most dogs recover sufficiently in a matter of hours to go home.

Because cannabinoids bind to fatty substances in your pet’s blood stream and body, a few veterinarians have attempted to treat severe marijuana overdoses with intravenous fat emulsions (e.g. Intralipid®), hoping it might “sop up” some of the drug. (read here) We do not yet know if this is helpful when cannabis is involved.

“None Of That Sound That Risky – So You’re Recommending We Try Some Of Our Stash On Our Sick Pet – Right?”


I don’t suggest you give your pet the marijuana products some of us humans consume. As for the CBD oils that veterinarians and online sources sell for pets and humans, most are probably harmless. None of them have ever been proven to work for anything other than to treat certain rare seizures in children when other medications fail. For that, the FDA approved Epidiolex®. As long as the psychoactive THC portion of marijuana/hemp (the “high” or euphoric portion) of what you buy is not over 0.3%, the FDA considers CBD oil to be a food supplement

As Dr. Kellogg, senior veterinary adviser to the Humane Society, is quoted as having said: “Sometimes public sentiment and activity gets ahead of the scientific background and that can be dangerous”. Veterinarians and others who recommend that you give the active compounds in marijuana at per-weight doses similar to human miss some important points: They are assuming that marijuana/cannabis is metabolized in dogs and cats the same way that it is in humans or the rats, mice and monkeys it was tested in. That is untrue. It has happened before. It took veterinarians quite some time to discover that pets metabolize the sugar substitute xylitol differently than we do.  It took us even longer to discover the dangers of giving our pets grapes or raisins. (read here & here)The same goes for chocolate and onions. (read here &  here) Some say that the ingredients in cannabis (chiefly THC and cannabidiol) are “practically harmless” because its LD50 (toxic dose) is very high (greater than 3,000 to 9,000 mg/kg). But those were one-time dose experiments – not the effects of long-term use.

Dogs And Cats Are Not Little People – They Metabolize Marijuana-Based Cannabinoids Quite Differently Than We Do

Most veterinary marketers get around this known danger by not including any of the medically active constituents of hemp in their products – or they keep the amounts of those chemicals at extremely low homeopathic (ineffective) levels.   

I want to tell you a long story if you will bear with me:

It began a long time ago and today has been pretty much forgotten. The medicinal properties of cannabis have been known by botanists and pharmacists since antiquity. (read here) But it wasn’t until 1964 that Raphael Mechoulam, an acquaintance of mine, and a colleague of his identified its primary active ingredient, THC in marijuana and hashish.  However, he and his colleague were not the only group curious about cannabis. The United States chemical warfare program had a keen interest in THC as well. (read here) Those folks were funding research designed to make “useful derivatives” of marijuana and judge their effects on people. As luck would have it their chief experimental “volunteers” were the stray dogs of Baltimore. That “interest” did not end until President Ford eventually discontinued all chemical weapons development. One of the ECBC contracts was given to the Pharmacy department at the University of Michigan to study several cannabinoids (DMHP, NAP and MOP). The first thing they noticed was that dogs were much more sensitive to the effects of cannabinoid compounds than monkeys. Two of the four dogs in one experiment died by the end of the 4th day of cannabinoid (DMHP) administration. Other ECBC-funded studies conducted elsewhere found that any stimulant in the dog’s system (caffeine, amphetamine, cocaine) or nalorphine concurrent with that cannabinoid, greatly increased the cannabinoid’s toxicity. (That still has relevance today. If one was uncertain what recreational drug a pet ate, nalorphine, might be given as well).  They also noticed that there was a great deal of variability in how a given dose would affect an individual dog. In the following years, many toxicity studies were performed on experimental animals. All found that dogs, mice, cats and monkeys behaved similarly when given a single dose of cannabinoids. The problem was, these were one-time doses. Rarely if ever were multiple doses given to see what occurred over time.

Let’s move on to 1975. New chemotherapy medications for cancer were coming on the market and drug companies were looking for ways to control the nausea these drugs caused. One of them was Eli Lilly Laboratories whose research center was in Indianapolis. But there was a major problem. This was the time of reefer madness. The Lilly chemists knew that cheap, garden variety Delta 9 THC worked quite well in controlling nausea. But there was no chance of getting FDA and DEA approval to market a standardized “pot” pill.  Just as importantly, Lilly would not have had a patentable product – one that could produce a rich revenue stream to justify their efforts. They were also hoping (mistakenly) that they could split off the anti-nausea effect of THC from the elation effect (even though a bit of elation in folks facing chemo might not have been such a bad thing). So, they zeroed in on a slightly different THC structure they had previously synthesized. It is called Nabilone. It gave the Federal Agencies and politicians the fig leaf they needed to approve a cannabinoid anti-nausea medication while still keeping marijuana illegal. In 1975, Lilly rounded up six male volunteers who were more than happy to get get high and paid for it as well and gave them nabilone. They pronounced the drug safe and its addictive potential minimal. However, a study like that was unlikely to satisfy the demands of the FDA and the DEA. They like voluminous (telephone directory-thick) animal studies to assure safety. One of those demands is usually to know the effects of a particular drug’s long-term use. So, Lilly began another study that included the long-term effects of nabilone. At the time, it was common to do those studies in stray dogs (euphemistically call “random source dogs”). Here is what they found: Dogs and monkeys absorbed nabilone at about the same rate. However, once in the body, the cannabinoid transformed (metabolized) in very different ways in dogs than in monkeys. Not only were different compounds formed; but these compounds (carbinol metabolites) accumulated in the brains of the dogs at levels 5–6 times higher than in the dog’s blood.  None accumulated in the brains of the monkeys. The dogs appeared OK during the three-months study. But in the one-year study, a considerable number of dogs died showing violent convulsions shortly before death. So many had died by the 7th month that the experiment was called off. Just as worrisome, dogs died at all dose levels. That is, it didn’t seem to matter very much how large or small the daily drug dose was. That is quite unusual in medicine; most toxicity problems are dose-dependent. None of these dogs still had high nabilone levels – it appeared to be the high carbinol metabolites that accumulated in their brains that killed them. It did appear that whatever eventually occurred took longer to occur when the daily dose was small, but it eventually occurred just the same. So, the Lilly tests had to be repeated – this time in monkeys that appear to metabolize cannabinoids more similarly to the way we humans do. In dogs, it appeared that nabilone was metabolized in the dog’s liver similar to the way it was in other species- but something farther down the line, perhaps the dog’s ability to eliminate the carbinol metabolites through its kidneys and liver were different in dogs than in humans and primates. In addition, we now know that even cannabis receptors differ between dogs and humans. (read here) What the Lilly researches saw in the dogs receiving cannabinoids = convulsions occurring without warning just before death, deaths not dependent on the size of the dose and nothing significant found at autopsy has many similarities to a syndrome seen in humans called serotonin syndrome.  It occurs when too many or two large a dose of medications that affect the brain are dispensed. (read here) Lilly’s dog results were worrisome enough to be communicated to Dr. Mechoulam in Jerusalem. He assigned one of his grad students, Emil Samara, to figure out what was going on in those dogs. What Dr. Samara found was that unlike in people, dogs combine large portions of the cannabinoids they ingest with glucose to form glucose conjugates. They did not find these “unusual glucoside conjugates” in rats given the same cannabinoid. This is probably one reason why the human urine drug tests are inaccurate in dogs. You can read the results of those studies and others I quote in this article if you ask me for them. I deleted them from the server hosting this site in 2020 for economy.

Perhaps your pet is not expected to live long enough to experience the possible side effects of real cannabis that concern me. Even then, its immediate comfort could be more important than the length of its life. Maybe you will be using what is basically a homeopathic amount of cannabis – too little to do much one way or the other. The world is full of those pseudoscientific (worthless) products. Maybe something similar to serotonin syndrome won’t occur in your pet – only a few seemed to develop it. It could also be that I am just wrong – Time will tell.

What About My Cat?

Now that you know how little we veterinarians know about how marijuana/cannabis might affect your dog, you should know that veterinarians know practically nothing as to how cannabis or CBD oil might affect your cat. 

What Cannabis/Marijuana Products Are Out There?


If you have read this far you already know what I think about the value of CBD oil. 

Natural Cannabis Products:

I live on the Texas border where anything that has to do with marijuana is dealt with severely. So, I know very little about the products found in more liberal states. For that, consult your local cannabis connoisseurs. But I do know that the cannabinoids in marijuana dissolve best in fatty substances (they are lipophilic). I also know that the overdoses veterinarians see are often associated with something called “cannabis butter”. That may be because the milk fat in butter serves as an efficient way to accumulate the active ingredients in marijuana and aids in absorption through the pet’s digestive tract. I also know that there is great variation in plant potency (strength) and that heating and drying apparently increases the availability of the cannabinoids in marijuana. There are also differences in the THC to CBD content and ratio between various strains of Indica marijuana and Sativa marijuana. 

You would probably be reluctant to take a medicine that you thought might cause side effects when you didn’t know how much you were taking. The same should be true for your dog or cat.

Synthetic formulas:

The primary advantage of these products is that their strength is known precisely and published studies have been performed to determine their toxic doses (but not in dogs or cats). That at least allows an actual known dose to be calculated.


I wrote a great deal about Lilly’s nabilone (Cesamet®) earlier in this article. It is currently a DEA Schedule II controlled substance. It is approved by the FDA for treating nausea and vomiting associated with chemotherapy when ordinary anti-emetics are not effective. Off-label (not government approved) uses in humans include treatment for fibromyalgia, multiple sclerosis (MS), chronic pain, and inflammatory bowel disease.


Dronabinol is sold as Marinol® by the Solvay Pharmaceutical Company. It is often called synthetic THC and appears to be no different from the THC found in marijuana (with the same effects and side effects). It is used in humans as an appetite stimulant, to prevent vomiting, as a treatment to combat the general decline of AIDS and to relieve pain. The DEA put it in Class III for now – until some sort of national marijuana policy is established.


Marketed as Sativex®, it is a mouth spray used to treat pain, multiple sclerosis and overactive bladder. It really belongs with the natural products because it is simply an extract of natural cannabis. It is in an alcohol base that some people (and probably pets-not that I suggest you give it) find objectionable. 

Delivery Systems and Treatment Plans:

I can’t be of much help to you with that. Dr. Robinson of the Center for Comparative and Integrative Pain Medicine at the Colorado State Veterinary School had some advice for me. She suggested contacting a member of the IVAPM (The International Veterinary Academy of Pain Management). I think that was excellent advice – certainly better than trusting what you read online or in the popular press or the advice you get at your local medical marijuana outlet. Topically applied cannabis seems to be a current rage. We know very little about the ability of these products to penetrate the skin or if they enter the blood once they do. If, for instance, they do penetrate the skin and if they only worked locally on local CB1 receptors, perhaps the brain effects that appeared to occur in dogs receiving cannabinoids orally might be avoided. We do not know. 

Might One Pet Handle Cannabis and Cannabinoids Better Than Another? Could There Be Interaction With Other Medications My Pet Is Receiving?

The answer to both questions is probably yes.

Your pet’s, age, concurrent medications and breed might affect its reaction to cannabinoids. Its current stress level might also. Cannabinoids are metabolized in your pet’s liver and excreted through its kidneys as well. So, any decline in the function of those organs will likely affect how it handles cannabinoids. Cannabinoids are most soluble in fat and lipids. So obese pets might experience different effects from the same dose given to a lean pet. Cannabinoids appear to decrease tear production. So breeds of dogs with bulging eyes (brachycephalic breeds) might be more susceptible to dry eye problems when on those medications. (the potential for eye problems is another good reason not to blow marijuana smoke at your pet).

Some pets are prescribed tramadol for pain. We know that humans are more at risk of serotonin syndrome when they take tramadol along with other medications.  Perhaps the same effect occurs in pets. Older pets often suffer mental decline as they age just as we do (CCDS). Veterinarians frequently prescribe selegiline (Anipryl®, Deprenyl®) for those pets. How that stimulant would interplay with the effects of THC within the brain is unknown.

Based on Astra Zenica studies (read here) it might be wise to monitor heart function,   liver function and kidney function in pets receiving cannabis products in meaningful amounts. Since hepatic steatosis was one side effect that was noted in people, hepatic lipidosis in cats would be another problem that might cross my mind. If you are giving cannabinoids to your cat to improve its appetite, Entyce®,   Elura® or mirtazapine might be better choices. Even over-the-counter CBD oils are not without risk. (read here)

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