The Animal Poison Control Center reports an increase in the number of calls about marijuana poisonings in pets, according to NBC News. Calls have increased from 213 in 2009, to 320 last year. It is likely many more cases go unreported, the article notes.

Dr. Matt Booth says his veterinary emergency center in Boulder, Colorado sees about a case of marijuana poisoning a month. Recreational marijuana recently became legal in Colorado. Dr. Monica Kaeble of the Pet Emergency and Specialty Care Center in La Mesa, California, says her practice sees about one or two cases of marijuana poisoning per week.

“Animals don’t react the same way as humans,” said Dr. Tina Wismer, Director of the Animal Poison Control Center. “They may become sedated, act drunk and wobbly, but about 25 percent go the other way. They become agitated, have high heart rates, they’re in distress. Most dogs become incontinent. They stagger around dribbling urine everywhere.” Their blood pressure can soar, and without treatment, dogs can go into a coma and die.

The most common way pets are poisoned by marijuana is by eating drug-laced edibles, such as cookies and brownies made with marijuana butter, prepared by owners for their own use.

A study published in 2012 found a significant correlation between the number of medical marijuana licenses and marijuana poisoning cases seen in two veterinary hospitals in Colorado.