From early 2005 to late 2009, Children’s Hospital Colorado had exactly zero emergency-room visits by kids who had ingested marijuana. In the following two years, when medical marijuana became legal in Colorado and federal officials backed off prosecution, it had 14.

Pioneering studies of ER charts by Colorado doctors show looser pot laws leading to childhood poisonings, often from mistakenly eating tantalizing “edibles” like gummy worms or brownies.

Those doctors are now helping lead the charge for mandatory safety packaging as Colorado gears up for even broader legal sales of pot with recreational-marijuana stores.

“We’ve seen a dramatic increase in pediatric exposure,” said Dr. George Wang, a Children’s ER doctor who also works with Denver Health’s Rocky Mountain Poison and Drug Center.

Calls about potential marijuana exposure at all ages have doubled since 2009 at the poison center.

Safety packaging, as in other medicines, “is a supplement to careful parenting that has been shown to work,” said Wang’s colleague, Dr. Michael Kosnett. “There are solutions available right now.”

And the marijuana industry agrees, up to a point.

Many industry members favor sending goods out the store door under tamper-proof seal. But they would rather not break each individual joint or candy into a high-tech, lockable bag whose cost — up to $7, even in bulk — might approach the price of the brownie inside.

“They’ll have to buy so much tamper-proof packaging that people will just make it themselves at home,” said Robin Hackett, co-owner of Botana Care, a medical-marijuana store in Northglenn. “The challenge is with a pound of butter and some cannabis, anybody can make edibles.”

Hackett and other members of the Medical Marijuana Industry Group say lockboxes and larger locking bags that buyers can use to transport larger purchases home should solve most of the safety problems.

Breaking everything down into smaller tamper-proof bags is a landfill problem and unnecessary expense, Hackett said. Botana Care counsels patients with children about safety, and keeps track of who has kids as a reminder.

“Unfortunately, we can’t write laws around ‘dumb,’ ” she said.

None of the accidentally poisoned children has died, Wang and Kosnett said.

There are serious medical consequences for small children, though, even while marijuana advocates say an adult “overdose” of pot is nearly impossible.

Prescribed dosages of THC, the active ingredient in marijuana products used to control nausea from chemotherapy, is between 4 and 12 milligrams for children ages 2 to 4, based on body surface area. Some “edibles” have 300 milligrams of THC, Kosnett said.

The researchers say individual safety packs would be best, but the current recommendation of all items leaving the store in one secure package is “better than nothing.”

Because there is no clear reporting category for marijuana poisonings, doctors have to cull through files to count cases. Presbyterian/St. Luke’s, which operates Rocky Mountain Hospital for Children, said it does not track similar cases.

The cases studied at Children’s included decreased levels of consciousness and breathing trouble. Children can also vomit from ingesting too much of a strong substance and aspirate the vomit.

The median age in the 14 patients was 3 years, and the range was 8 months to 12 years, according to an abstract of the research published in the journal Clinical Toxicology.

Child-ingested pot is also dangerous because ER doctors aren’t looking for it as a cause of any symptoms they see, Wang said. That can lead to invasive and expensive diagnostic efforts, such as a spinal tap or CT scan, if parents are embarrassed or scared to mention the true cause.

“When children get admitted to the ICU, that’s serious,” Kosnett said. Symptoms may appear similar to meningitis, for example.

Safety packaging and parental prevention should be noncontroversial, said Dr. Robert Brockmann, president of the Colorado Academy of Family Physicians, especially as newly legal recreational use will greatly expand the supply.

“None of that information is being disseminated when it’s dispensed,” Brockmann said. “It’s like liquor or prescription medications, or anything else you don’t want your kids to get into.”

Kosnett likens the social moment to that of the 1970 U.S. Poison Prevention Packaging Act, which launched many of the safety containers now ubiquitous in medical and chemical markets. One standard for packages, Kosnett said, is that no more than 20 percent of 5-year-olds be able to open a container within 10 minutes.

Such measures have cut pediatric poisonings in various categories by 40 to 90 percent over the decades, he said.

Michael Booth: 303-954-1686, mbooth@denverpost.com or twitter.com/mboothdp