In the largest disciplinary action taken against medical marijuana doctors to date in Colorado, the state Medical Board on Tuesday suspended the licenses of four doctors for allegedly recommending excessive plant counts to more than 1,500 patients.

All of the recommendations involved approvals for patients to grow or possess at least 75 plants. The standard plant count for medical marijuana patients is six plants, and state health officials have long threatened to crack down on doctors who they believe recommend higher amounts without sufficient justification.

While the Medical Board has previously disciplined doctors one-by-one for problems related to medical marijuana recommendations, Department of Regulatory Agencies spokesman Vincent Plymell said Tuesday’s suspensions are the first time the board has suspended multiple licenses at once over medical marijuana.

The suspended doctors are:

Dr. Gentry Dunlop, of Aurora, who was first licensed to practice medicine in Colorado in 1988

Dr. Robert Maiocco, of Denver, who was first licensed to practice medicine in Colorado in 1997

Dr. Deborah Parr, of Durango, who was first licensed to practice medicine in Colorado in 2009

Dr. William Stone, of Colorado Springs, who was first licensed to practice medicine in Colorado in 2010

Suspension orders for each say the punishments will last “until resolution of this matter.” Dunlop is accused of issuing medical marijuana recommendations authorizing 75 or more plants to at least 700 patients. Maiocco is accused of making such recommendations to at least 190 patients, Parr to at least 300 patients and Stone to at least 400 patients.

Attorney Robert Corry, who represents Dunlop and Maiocco, criticized the suspensions, saying they were issued without his clients being given the chance to present their sides. He said he plans to ask for a hearing on the suspensions and could file a lawsuit.

“This has nothing to do with medicine,” he said. “This suspension has nothing to do with facts and nothing to do with the law. It’s all about politics.”

Stone said he first found out he was under investigation on Tuesday, at the same time he was notified of the suspension. He said only then did the Medical Board ask for patient records to investigate more thoroughly.

“It’s guilty until proven innocent,” he said.

Because marijuana is a federal Schedule 1 controlled substance, doctors cannot prescribe marijuana to patients. Instead, doctors in Colorado recommend the use of marijuana to patients suffering from one of eight conditions, the first — and sometimes only — step for people to become legal medical marijuana patients.

The state constitution says medical marijuana patients may grow six cannabis plants but also allows doctors to recommend higher plant counts for patients if it is “medically necessary.” Medical marijuana advocates say some patients need the higher counts to make edibles or concentrated marijuana oils. Law enforcement officials worry the high plant counts could be cover for illegal diversion.

State Health Department policy is to refer doctors to the Medical Board for investigation if doctors recommend an increased plant count for more than 30 percent of their medical marijuana patients.

The suspension orders for the four doctors put special emphasis on whether the recommendations were issued to patients diagnosed with cancer. Without a cancer diagnosis, the Medical Board alleges a recommendation for more than 75 plants, “falls below generally accepted standards of medical practice and lacks medical necessity.”

It is unclear, though, where that standard comes from. When asked, Plymell referred The Denver Post to the state constitution and statutes and Health Department rules, none of which tie the plant counts to a cancer diagnosis.

Stone said he has recommended high plant counts to patients with multiple sclerosis or severe migraines. He said higher counts are needed because some patients develop a tolerance. Others, he said, are just bad at growing and need approval for more plants to account for those they’ll kill.

With his license now suspended, Stone said he can’t see his regular patients anymore in his neurology practice.

“This is extremely painful for me as a physician and my ability to practice and take care of people,” he said.

Corry said the Medical Board provided no justification for why plant counts over 75 should subject doctors to discipline.

“These are distinguished doctors with solid careers who are probably now forever tainted by this,” he said.

Recommendations for high plant counts are rare.

There are currently 106,066 licensed medical marijuana patients in Colorado, according to state Health Department figures accurate as of May 31. Of those, 91,597 — 86 percent — hold recommendations for no more than six plants. Only 477 patients — less than half of a percent — hold recommendations for 76 or more plants, according to the Health Department figures. Another 1,324 have recommendations for between 51 and 75 plants.

Neither Dunlop nor Maiocco have been disciplined by the Medical Board before. In 2010, the board sent Parr a letter of admonition after medical officials in Texas reprimanded her for inappropriately prescribing opiates to two patients with histories of substance abuse. The Colorado Medical Board sent Stone a letter of admonition in March criticizing him for performing, “several patient evaluations for medical marijuana via the internet.”