Like many captive elephants, Nidia had chronic foot problems. Fissures had formed in the 55-year-old Asian elephant’s foot pads, and her toenails had cracked and become ingrown. Painful abscesses lingered for months. Nidia had lost her appetite, and she was losing weight.
Dr. Quetzalli Hernández, the veterinarian in charge of Nidia’s care at a wildlife park in Mexico, was desperate. She decided to try cannabidiol, or CBD, the nonintoxicating therapeutic compound found in cannabis.
For help, Hernández reached out to Dr. Mish Castillo, chief veterinary officer at ICAN Vets, a company engaging in veterinary cannabis education and research in Mexico. To Castillo’s knowledge, no one had purposely given an elephant medical cannabis. But he and his colleagues hoped it would reduce Nidia’s pain and stimulate her appetite, as they had seen the drug do for cats, dogs and other species.
They started low and eventually settled on a dose of 0.02 milligrams of CBD per pound of Nidia’s weight, which she took daily with a chunk of fruit. Calibrated by weight, the dose is one-tenth to one-fortieth of what Castillo gives to dogs or cats. Yet, it worked.
The first sign that the treatment was effective was when Nidia developed a serious case of the munchies. Within days of starting CBD, she went from finishing just one-third of her food to virtually all of it, and sometimes even went for seconds. Within five weeks, she had gained 555 pounds.
After Nidia began eating, her demeanor changed. “She was always known as the grumpy one — she used to kick doors,” Castillo said. “Within the first week to 10 days of her treatment, she started coming out of her enclosure quicker and was in less of a bad mood.”
Nidia’s abscesses also began to heal, probably as a result of CBD’s anti-inflammatory effects. For months, the pain in her feet had prevented the elephant from walking down a small hill to a drinking fountain in her enclosure, forcing her handlers to give her water in buckets and by hose. As her condition improved, she started to visit the fountain again.
“She just continued to get better,” Castillo said. “We were amazed that this happened at such a low-response dose, which led us to want to get this information out before veterinarians start overdosing other species by using the dog or cat dose.” Correct dosing comes down to species-specific differences in metabolism and variability between individuals, he added.
Medical cannabis for humans is legal and commonly used in a number of countries and U.S. states. But its adoption in veterinary practices has lagged behind human medicine. Dozens of scientific studies point to cannabis’ potential for treating seizures, pain, anxiety and fear, mostly in dogs. Mounting anecdotal evidence from countries such as Mexico, where veterinarians can legally administer the plant or its compounds, suggests benefits across a variety of other conditions in species as varied as parrots, turtles and hyenas.
But despite the promising findings, challenges abound for introducing cannabis into veterinary medicine: confusion about the law, lingering drug-related stigma, a lack of education and a dearth of peer-reviewed studies. In most countries, including the United States, prohibitive or incomplete legislation also hampers veterinarians’ abilities to study and use cannabis in their practices.
“People are very interested in alternative therapies that work better” and have fewer side effects, said Dr. Stephanie McGrath, a veterinary neurologist at Colorado State University who studies medical cannabis and is on the scientific advisory board of Panacea Life Sciences, a CBD product manufacturer. “We really should be funneling dollars to support research so we can get a better understanding of how we should be using this medication,” she added.
Laws in places such as California have begun to make way for veterinary cannabis. And a small but growing number of international veterinarians have united to bring cannabis into mainstream veterinary medicine through education, research and activism.
“Our countries are all going at different paces for regulation and legalization,” Castillo said. “But we can work as a worldwide network of veterinarians to further advancements together.”
Cannabis contains 100-plus chemical compounds, but CBD and tetrahydrocannabinol (THC) are the molecules whose therapeutic effects are best understood. While CBD does not discernibly alter consciousness, THC is responsible for the “high” associated with smoking or ingesting marijuana.
Across vertebrate species, these molecules interact with the endocannabinoid system, a network of nerve receptors, molecules and enzymes that keeps the body’s other organ systems stable. When used medically, cannabis essentially “supports the support system,” said Dr. Casara Andre, founder of Veterinary Cannabis, a Colorado-based group that provides education and certification to animal care workers and consultation services for pet owners and the cannabis industry.
A number of countries now legally permit veterinarians to prescribe and administer cannabis. In terms of research and adoption, though, Mexico is emerging as a world leader. Since 2019, Castillo and his colleagues have trained about 1,500 veterinarians in medical cannabis use.
Dr. Mónica Lozano Garza, a veterinarian in Toluca, Mexico, said she was not among the early adopters. But in 2020, her Old English sheepdog, Patricio, would sometimes wake up gasping for breath because of an inflammatory disorder in his nasal cavity.
When other treatments failed, Lozano reached out to Castillo, who helped her obtain a personalized CBD formula for Patricio from a company he advises.
“You have no idea how much it helped; he could breathe again,” Lozano said. “He got 2 1/2 more years of life.”
Lozano has treated about 65 animals with CBD since then. She has used it to relieve pain, to help with gastrointestinal issues and to take asthmatic cats off steroids.
She has also given CBD to animal patients that become stressed during office visits. The easiest way to administer treatment in these cases, she has found, is to nebulize the CBD and essentially create a carrier-size hotbox for the anxious cat or dog.
Cannabis can be combined with conventional pharmaceuticals to improve those drugs’ results, veterinarians have found. And in some cases, given on its own, cannabis has outperformed existing drugs, said Emma Delaney, a pharmacist and sales manager at CBD Vets Australia, a company that provides education and medicinal cannabis to veterinarians in Australia.
In 2023, for example, a 48-year-old rose-breasted cockatoo named RiffRaff was hospitalized in Australia after she stopped eating and was exhibiting signs of pain in connection with a pancreatic cancer diagnosis. Four prescription drugs, including an opioid, failed to improve her condition. “She was not expected to live beyond the week,” said Leah Jigalin, RiffRaff’s owner, who adopted the bird from her grandmother.
Euthanasia would normally be the next step, but Jigalin asked about trying CBD. Within a week, RiffRaff’s appetite returned, her demeanor improved and she was chirping again. She could stop taking the prescription medications, “which she absolutely hated,” Jigalin said, and she has remained in good health with the support of two daily doses of CBD oil.
When RiffRaff sees the plastic syringe coming, “she chirps and taps her foot, which is her happy dance,” Jigalin said. “One hundred percent, she knows that the medicine makes her feel better.”
While most veterinarians focus on cannabis for pets, those in Colombia, Castillo said, have taken the lead on using it for zoo animals.
Dr. Diana Buitrago, a veterinarian at the Cali Zoo, estimates that she and her colleagues have given cannabis to more than 50 species — from mountain tapirs and lions to snakes and capybaras — since 2020. They have found that CBD works well for pain, inflammation, osteoarthritis and allergies and that it can also enhance the effectiveness of treatments for conditions such as cancer.
THC, on the other hand, usually gives better results for patients at the zoo struggling with stress and anxiety, Buitrago said. It helped bring relief to a parrot who was plucking out her feathers, for example, and a jaguar who was obsessively pacing his enclosure and biting his tail. “We tried everything with him, but nothing seemed to work until cannabis appeared in our lives,” Buitrago said.
Regardless of the species, veterinarians who work with cannabis emphasize the importance of starting with small doses and then working up incrementally to find what works best. “Cannabis medicine is more challenging for me than oncology is, because in oncology, there is a protocol to follow,” said Dr. Trina Hazzah, a veterinary integrative oncologist and co-founder and president of the Veterinary Cannabis Society, an advocacy and education group in California. “Cannabis is so personalized.”
Ideally, veterinarians and pet owners work together through trial and error to determine the best regimen for the animal. Castillo, for example, encourages owners to keep a diary when starting their pet on CBD, noting their animal’s moods, symptoms and levels of sleeping, eating and playing. “That gives us a good idea of how the patient is doing, day by day,” Castillo said. “It helps us adjust the treatment and get better results faster compared to just saying ‘Take two as needed.’”
Veterinarians who are able to legally administer cannabis are still the exception. In most countries, the drug is still illegal or unregulated for veterinarians. In some U.S. states, including Georgia and Alabama, veterinarians are legally prohibited from even talking about cannabis with pet owners. Although Hazzah has not heard of any veterinarians losing their licenses for discussing cannabis with clients, she said she has heard of some receiving cease-and-desist letters from medical boards.
Veterinarians regularly administer medications approved for humans to their animal patients, Andre said. Yet, veterinarians are frequently overlooked in legislation permitting the use of medical cannabis, which usually addresses only human patients, she added.
After years of lobbying in the United States, Hazzah and others have gotten some states to update their laws. In 2022, California passed a bill that permits veterinarians to recommend such treatments to clients. Even in California, though, many veterinarians are still unclear on the rules, Hazzah said. “Not only is it confusing what their rights are, but they are not even informed these rights exist.”
Pet owners in the United States who ask their veterinarians about cannabis might find them unwilling to discuss the subject for fear of punishment, Hazzah said, or unable to do so for lack of knowledge. Some veterinarians, including Hazzah, who also sometimes consults for cannabis companies, are trying to fill this gap by offering veterinary cannabis consultation services for pet owners.
It can be dangerous for pet owners to try to medicate their pets with cannabis products without professional guidance, Hazzah added. In dogs, for example, too much THC can cause side effects such as incontinence, lethargy, paranoia, vomiting and a comalike state.
“With marijuana being so ubiquitous now, most days in the ER, we see an intoxicated animal,” said Dr. Shelly Pancoast, an emergency veterinarian and a former president of the Rhode Island Veterinary Medical Association. For this reason, Pancoast and her colleagues opposed a 2023 state bill that would have permitted Rhode Island dispensaries to sell THC-containing marijuana products for pets.
Education for veterinarians is also warranted, Andre said, about the medical use of cannabis and the endocannabinoid system, which recently entered the curriculum at veterinary schools after being discovered in 1988. “We’re running into the need to get a new paradigm into the veterinary industry,” she said.
Although things are moving slowly, Castillo said, each year brings more research findings, training courses and mentorship programs, as well as international collaborations.
Castillo and his colleagues, for example, are preparing to publish another case study about CBD use in a ferret named Macarena. The ferret fell from a fifth-floor balcony in 2017, causing severe spinal trauma and chronic pain. She was put on opioids, but persistent discomfort caused her to self-mutilate. “She basically chewed her own back legs raw from the pain,” Castillo said.
Veterinarians amputated her back legs, but Macarena continued to show signs of distress, including by biting her abdomen.
Four years after her fall, Macarena found relief through CBD. At a dose of 0.3 milligrams of CBD per pound of her body weight, she stopped self-mutilating. She gained weight and became more active, Castillo and his colleagues said, and she was able to discontinue the use of opioids.
Macarena died in September from old age, and right up until her death, the researchers reported, she was in good spirits.