By Rachel Nuwer
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.
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.
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.