When Tank, a 3-year-old male pit bull mix, arrived with his owner at a veterinary office in Humboldt County, his jaws packed with white powder, it was clear that something was seriously wrong.

Earlier, Tank had mysteriously consumed an entire box of baking soda -- odd behavior, even for an animal with famously indiscriminate eating habits.

But more disturbing was Tank’s demeanor. He sat trembling, his front legs stuck out at an awkward angle, his dilated eyes fixed on a distant point. A check of the heart revealed a coma-like 32 beats per minute, far below normal.

Joseph Humble, the attending veterinarian, suspected poisoning. But from what? The dog’s owner pleaded ignorance. Tank, distracted, wasn’t saying.


A few minutes later, the mystery was solved. “The guy called me right back and said, ‘Doc, I know what happened,’ ” Humble recalls. “ ‘The dog ate some pot -- kind of a lot of pot.’ ”

Marijuana’s action on humans is well understood: Once its psychoactive agent, tetrahydrocannabinol, better known as THC, is carried from the lungs or stomach by blood to the brain, it binds to nerve cells and activates the brain’s pleasure centers. Effects include sensory sensitivity, motor impairment and an increased desire for Doritos.

The plant’s effect on canines is considerably less benign. Even a few grams can cause staggering, vomiting, urinary incontinence and, in severe cases, seizures and coma. “Some people may enjoy pot, but I assure you dogs do not,” Humble says.

Although no statistics are kept on marijuana poisonings, the nation’s canine-to-pot ratio reveals potential for a problem. The American Pet Products Manufacturers Assn. estimates that 43 million U.S. households include a dog, while more than 25 million Americans fessed up on a 2003 government survey to having used marijuana at least once in the previous year.


In Northern California, which is believed to have the highest concentration of medical marijuana users in the country and where pot cultivation is a popular hobby, vets face a preponderance of such cases, with some attending to several zonked-out dogs a week.

But unlike in human medicine, where entire textbooks are dedicated to doctor-client communication, there are no such rules for vets, leaving them to their own strategies for broaching a touchy question: Any chance the dog ate your stash?

Because marijuana toxicity can resemble the early stages of a life-threatening poisoning by garden chemicals or antifreeze, identifying the toxin quickly is critical. But due to pot’s shaky legal status, many people are reluctant to admit that their pet is stoned, and most vets choose to skirt the issue rather than confront owners.

“The classic question is, ‘Do you have teenagers?’ ” says Edward Haynes, a Mendocino County veterinarian who sees a spike in such cases during the fall pot harvesting months. “Then you say, ‘Is it possible that the dog came in contact with any recreational drugs?’ ” he says.


Owning up to the truth

Even in cases where the owner admits that the dog was exposed to pot, many are still reluctant to take responsibility. Humble, who says he treats dozens of marijuana poisonings every year, says, “It’s always a roommate’s or the neighbor’s. It’s never theirs.”

As was the case with Tank. His owner explained to Humble that his roommate had baked a tray of potent marijuana cookies, leaving a warning that consumption should be limited to a quarter of a cookie. Left alone, Tank gobbled the entire batch. And the baking soda? “The animal had the munchies,” Humble says.

Jeffrey Smith, a vet at Middletown Animal Hospital in Middletown, Calif., says he engages in profiling to aid diagnosis. “The majority of these cases, they tend to be young people, sort of ‘living life and loving it’ types,” he says. “They come in two or three at a time with one pet, kind of nervous and looking at each other.”


Other vets employ a mild form of blackmail. In cases where marijuana poisoning is suspected but not owned up to, some vets explain that if a more innocuous poison cannot be identified, their pet will need a full treatment of intravenous fluids, a stomach pump and an enema -- costing the owner hundreds of dollars, not to mention a seriously bad trip for the dog. “About two-thirds of people, you have to kind of squeeze it out of them,” says Smith.

Once marijuana poisoning has been established as the cause of the patient’s distress, vets say the best approach is to monitor the dog’s vital signs and wait. “Most of the time, they do fine if you just let them sleep it off, just like people,” says Haynes.

Because of the importance of distinguishing marijuana toxicity from other poisonings, some vets call the 24-hour poison hotline run by the ASPCA Poison Control Center in Urbana, Ill. Since 1998 the center has consulted on about 600 cases of marijuana toxicity among animals from around the country, with New York and California leading the list.

More than 95% of cases involved dogs, a disparity that does not surprise veterinarian Caroline Donaldson, an ASPCA consultant who has written about marijuana toxicity for the journal Veterinary Medicine. “Dogs eat anything and everything. It’s the nature of the beast,” she says.


Although canines are clearly on the front lines of the pot-versus-pet drug war, the ASPCA has documented a handful of cases involving cats, rabbits and horses. Humboldt County vet Judy Horvath once treated an iguana that fell unconscious after snacking on some buds supplied by its owner.

“We had to hook it up to an electrocardiogram to even find a heartbeat,” Horvath says. The iguana came to several days later, shaken but alive.

Is it animal abuse?

Such cases bring up the question of legal responsibility. Although 12 states, including California, have decriminalized marijuana, the federal government still classifies pot alongside heroin and LSD as among the most dangerous Schedule 1 controlled substances. In addition, a 2004 California law obligates vets to report cases of animal abuse or neglect, which could include animals irresponsibly exposed to toxins.


Melissa Stallings of the California Veterinary Medicine Assn. says, “It’s really up to each vet to make a common-sense call. They have to ask, does it rise to the level of abuse?” So far there have been no reported cases of a vet turning in a pet owner for pot-related abuse.

Smith sums up the feelings of many vets regarding their role in drug law enforcement. “My only concern is the animal,” he says. “I don’t have to be the local cop as well as the local vet.”

Others feel obliged to take it further.

“A lot of times a kid will stash some pot in his room and leave the door open. In goes the dog and out goes the evidence,” Haynes says. Once marijuana poisoning is established, he says he feels obligated to inform parents, if only to protect a dog with impaired short-term memory. “I’ve busted a lot of teenagers that way.”