Supplements’ toxicity risks not easy to determine as new, reformulated products hit shelves
Products marketed as supplements have been gaining in popularity, not only for people but for pets as well.
At the same time, some of these products include substances that can be toxic for dogs and cats, and related calls to animal poison control have become very common, says Dr. Renee Schmid, director of veterinary medicine and senior veterinary toxicologist for the Pet Poison Helpline (PPH). Many times, veterinarians aren't sure what ingredients are of concern, she said.
In addition, veterinary supplements, especially those that are flavored and chewable, may cause metabolic effects, such as osmotic fluid shift.
Dr. Schmid gave a rundown of what practitioners should look for in her presentation, "Too Much of a Good Thing? The Potential Fatal Effects of Supplements," on September 13 during the American Animal Hospital Association’' Convention in Chicago. She is a diplomate of the American Board of Toxicology and the American Board of Veterinary Toxicology.
Veterinary supplements
L-tryptophan can be found in products marketed as supplements for pets, often indicated for "calming." However, at high concentrations, it can affect the gastrointestinal (GI) and central nervous systems (CNS). In dogs, clinical signs such as body tremors, depression, ataxia, vocalization, vomiting, and hypersalivation can develop early, anywhere from 10 minutes to an hour, and the patient can be symptomatic for several days.
Aside from decontamination, monitoring electrolytes, and fluid therapy to treat l-tryptophan toxicosis, Dr. Schmid will give acepromazine for sedation, cyproheptadine for its antiserotonin properties, and methocarbamol for tremors. Because cyproheptadine is only available in an oral form, the tablets can be crushed, mixed with saline, and given as a rectal slurry if the patient is not stable for oral administration. If seizures develop, Dr. Schmid will also administer anticonvulsants.
Other ingredients to watch out for in cases of supplement overdoses are glucosamine and manganese, she said. Not only can an overdose of either of these ingredients affect the GI system and CNS, but they can cause liver failure. Bloating is common along with hypernatremia. Along with decontamination, monitoring electrolytes and liver enzymes, fluid therapy and hepato-protectants are recommended for treatment, such as acetylcysteine.
"Grass saver" chews are frequently sold to pet owners who don’t want their grass discolored from pet urine. However, Dr. Schmid said they can really pose an issue, especially because they contain methionine, a urine acidifier in pets. If ingested in high amounts, animals can develop tremors and seizures within a few hours, which can last up to two days. Treatment is supportive care.
"The back label of one of these products said, 'If there is still grass discoloration, replant grass.' That's probably your best treatment for discolored grass and leave the supplements in their bottle," she said.
Human supplements
Human dietary supplements are the No. 1 source of elemental iron exposure calls to the PPH, said Dr. Schmid.
Adult’s and children's multivitamins often don’t have more than 18 mg of iron per tablet, but she advised veterinarians to watch out for prenatal multivitamins and standalone iron supplements that often contain a higher amount of iron.
Dr. Schmid said exposures of 20 mg/kg elemental iron or less are not a big concern, while exposures greater than 20 mg/kg can result in moderate to severe signs of toxicity in dogs and cats.
Typically, there are four stages of clinical signs. The first stage is GI upset, such as abdominal pain and a bloody stool, within one to six hours. In the second stage, the patient may appear to be fine six to 24 hours after exposure. However, in the third stage, between 12 and 96 hours, patients experience more significant GI signs, including cardiovascular collapse or liver failure. The fourth stage is recovery, and it can take two to six weeks for the patient to recover.
Regarding diagnosis, Dr. Schmid said, "If you see GI signs, that's what makes it or breaks it for me." She also recommended evaluating for elevated serum iron levels four to six hours after ingestion.
When treating, beyond inducing vomiting when ingestion is recent, followed by an antiemetic and GI protectants, she recommends milk of magnesia, administered three times a day, which helps remove iron from the gut. Chelation may be an option, too, in more severely affected cases.
Another ingredient of concern found in human supplements is alpha-lipoic acid, an antioxidant that goes by many names. Dr. Schmid recommends looking for the word "lipoic" on the product label. Cats are 10 times more sensitive than dogs, to the point that a very small exposure is considered toxic.
Onset of vomiting, ataxia, tremors, and seizures can occur within a few hours and last for days. Practitioners should monitor blood glucose, as profound hypoglycemia is often present.
Fluid therapy, anticonvulsants, methocarbamol for tremors, and hepato-protectants are indicated for treatment, she said. Extracorporeal therapy has not been shown to be effective.
Additional considerations
A common ingredient that veterinarians already know to look for, xylitol, also can be found in human supplements. The biggest concern here is with flavored liquid, chewable, and quick-dissolve products.
"If it's flavored, I'd look for xylitol," Dr. Schmid says. "Products are always changing, so it could be added when it wasn't there before."
In addition, Dr. Schmid says it's always good to ask the owner if their pet has ingested any packaging, to bring in the supplement container so you can see the label, and if they have already started any treatment at home. Other reminders she gave:
- Read ingredient labels carefully. Some ingredients are listed only in elemental form.
- Recognize main ingredients of concern.
- Don’t forget to look at inactive ingredients.
"The reality of veterinary medicine is animals don’t read the book in a lot of cases," she said. "Whereas the most common signs happen in a couple of hours, some will display signs later and it is important to remember to treat the patient, not the toxin. The toxin will certainly guide therapy, but it is the patient's clinical signs that ultimately dictate their therapy needs."
Oclacitinib overdoses a growing concern
Though not a supplement, oclacitinib maleate, a Janus kinase (JAK) inhibitor, should be used judiciously for pets by veterinarians.
An article published earlier this year by veterinarians at the Pet Poison Helpline (PPH) in the Journal of Medical Toxicology found that since the first flavored JAK inhibitor medication debuted in October 2023, there was a nearly 300% increase in calls to the hotline from overdoses in 2024 compared with 2023.
"Of the 417 symptomatic cases reviewed, 63 cases were symptomatic cats, and 354 cases were symptomatic dogs. Multi-system organ involvement, including neurological, gastrointestinal, cardiovascular, renal, hepatic, and ocular signs, as well as laboratory abnormalities were observed," the authors wrote.
"It's a great drug that I would readily give to a pet that would benefit from its use, but with the JAK inhibitors, we're continuing to see an increase in exposure calls," says Dr. Renee Schmid, director of veterinary medicine and senior veterinary toxicologist for the PPH. "They will continue to be used in human and veterinary medicine. There is a place and need for them, but now it's educating to recognize the severity of [overdoses]."