AP

DENVER (AP) — Colorado plans to crack down on medical marijuana patients, state health department authorities announced Friday, saying it would challenge patients and medical pot growers with permission for more than six plants.

The head of the state Health Department, Dr. Larry Wolk, announced Friday that those so-called "high volume" patients and their designated caregivers will have to show physician justification for "medical necessity" waivers.

Colorado has about 5,000 designated "caregivers," people with permission to grow pot on behalf of a medical marijuana patient.

Colorado limits caregivers to five patients and 30 plants and requires them to have significant responsibilities for caring for their patients. But 24 caregivers have waivers to grow higher amounts because they've been granted "medical necessity" waivers. One caregiver has 84 patients, Wolk said.

Wolk said Friday that the Health Department questions the medical necessity for more than six pot plants per marijuana patient. The agency plans to crack down on those high-volume caregivers.

Wolk argued that a high-volume caregiver "is in fact a small unlicensed business" and should instead apply to become commercial marijuana growers. Commercial growers must pay licensing fees and undergo criminal background checks, which aren't required of caregivers.

A bill to make that change is expected to be introduced in the Legislature next week.

Colorado's pot-legalization measure approved in 2012 did not dismantle the medical registry. The state Health Department oversees the medical marijuana registry, which had about 110,000 patients at the end of January.

The Health Department wasn't sure how many of those medical marijuana patients have "medical necessity" waivers to exceed the state limit of six plants per patient. Wolk argued that there isn't adequate research to justify the higher marijuana plant counts.

"Single plants can produce significant amounts of usable cannabis," Wolk said.

However, the crackdown sparked a fiery backlash from about 80 marijuana activists who criticized the change at an informal listening session at the state Capitol.

"This is criminal and this is mean," argued Jim Clark Jr., a high-volume caregiver. Clark says marijuana patients are best treated with oils and concentrates that require large amounts of raw pot. He said that regulated caregivers have never been accused of diverting pot to the black market since the state medical marijuana system was adopted in 2000.

"We don't sling pot to the other states," Clark said.

Others argued that Colorado simply wants to drive medical marijuana patients to the recreational market, where taxes are higher.

Colorado's caregivers are already prohibited from making a profit under a law adopted in 2010. But private caregivers can recoup expenses without paying sales or excise taxes, while commercially grown recreational pot if taxed at least 27.9 percent, in addition to local taxes..

"Let's just get off the greed bandwagon," marijuana activist Timothy Tipton said.

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Kristen Wyatt can be reached at http://www.twitter.com/APkristenwyatt