WASHINGTON -- Doctors in every state in the U.S. have the right to recommend medical marijuana for patients with a qualifying condition, such as cancer or HIV, but they can find themselves in legal hot water if they actually prescribe it -- even in those states where medical marijuana has been legalized.

That's because although the First Amendment right of free speech allows physicians to recommend medical marijuana, under a 2009 decision by the 9th Circuit Court of Appeals, they may not say or do anything to help patients obtain the drug, according to Joshua Murphy, JD, of the Mayo Clinic Legal Department in Rochester, Minn.

Murphy gave clinicians a primer on the do's and don'ts in the new -- and expanding -- playing field of medical marijuana, during a panel discussion here at the American Academy of Pain Medicine meeting.

"Fifteen states and the District of Columbia have laws permitting the use of medical marijuana," Murphy explained. Those states are Alaska, Arizona, California, Colorado, Hawaii, Maine, Michigan, Montana, Nevada, New Jersey, New Mexico, Oregon, Rhode Island, Vermont and Washington.

But even if a doctor doesn't live in those states, medical marijuana may still impact his practice -- especially if he lives in a border state, he said.

Murphy's talk highlighted a panel at the AAPM meeting that tackled the thorny problem of medical marijuana, complicated by varied state laws legalizing it and federal laws that ban it.

Despite an October 2009 Justice Department memo to U.S. Attorneys stating that federal resources should not be used to prosecute individuals in "clear and unambiguous" compliance with state medical marijuana laws, Murphy cautioned that there's always a chance the Obama administration (or subsequent administrations) will change that position.

In general, Murphy said doctors who are contemplating medical marijuana use for their patients should adhere to these rules to avoid criminal prosecution:

Know and comply with state laws on medical marijuana.

Recommend medical marijuana only in the context of a bona fide physician-patient relationship.

If possible, provide copies of medical records that include a medical marijuana recommendation, rather than completing a separate form or certification. Murphy said doctors who certify that patients should receive medical marijuana might be viewed as abetting the prescription of the drug which is illegal under most state laws.

Don't "prescribe" medical marijuana -- refrain from specific directions regarding amounts, methods of delivery, or time of use.

Do not direct patients to specific dispensaries or other sources of medical marijuana.

Do not confirm their recommendation with the patient's medical marijuana provider.

In cases where doctors practice near state borders, make sure the medical license and the patient's residence are both in a "legal" state. Only Oregon and Montana allow patients from any state to obtain medical marijuana.

Murphy also said that doctors who recommend medical marijuana have to be cognizant that they may also have malpractice liabilities as well.

For example, he suggested that doctors may be at risk if:

They recommend medical marijuana without performing an adequate patient history, examination and diagnosis.

They fail to follow-up and monitor the patient using medical marijuana and modify treatment accordingly.

They fail to disclose risks of medical marijuana, including side effects, drug interactions, and effects on preexisting conditions.

Doctors can also get into trouble with their state medical boards over medical marijuana.

To avoid those problems, Murphy suggested, "Doctors should approach medical marijuana recommendations the same as -- or more conservatively than -- opioid prescription."

Medical marijuana has been used for "debilitating medical conditions" generally defined to include HIV, cancer, glaucoma, cachexia, chronic pain, chronic nausea, spastic disorders such as multiple sclerosis, seizure disorders such as epilepsy, GI disorders such as Crohn's disease, arthritis, and migraine, according to Murphy's presentation.

However, before recommending any use of the drug, Murphy advised that:

Doctors should take a thorough history, including review of prior records and consultation with the patient's primary physician.

Doctors should perform a physical examination.

They should develop a treatment plan with objectives.

They should periodically review treatment efficacy at follow-up appointments.

Doctors should make sure the underlying reason for recommending medical marijuana is being treated.

Doctors should obtain and -- he stressed -- document informed consent regarding possible side effects of medical marijuana use.

Murphy noted that no law requires doctors to recommend medical marijuana for their patients nor are doctors required to accept medical marijuana users as patients.

The moderator of the panel, Mike W. Hooten, MD, assistant professor of medicine at the Mayo Clinic, noted that a few studies "have shown some benefits in treatment with smoked marijuana, but these were all small trials, and in all of the trials the study period was five days. Five days of active treatment may not be long enough to totally consider long-term effects, both from a pain perspective but also from an adverse side effect perspective."

He said other studies indicate that any benefits accrued in pain relief by smoking medical marijuana may be offset almost completely by adverse effects.

Terry Schneekloth, MD, an addiction psychiatrist at Mayo, said, "We are aware that cannabis can relieve pain, control nausea, stimulate appetite, decreasing ocular pressure and is associated with suppressing muscle spasms."

However, Schneekloth said marijuana smoke includes more tars than cigarettes, and marijuana does not come with cigarette-type filters, has 50% to 70% more hydrocarbons than tobacco smoke, and is associated with more cough and other lung illnesses.

He said that about 9% of marijuana users become addicted to the substance -- although that percentage rises to 25% of people who use it on more or less a daily basis.

The pharmacokinetic mechanism of action for marijuana or cannabis was described by Ajay Wasan, MD, director of clinical pain research at Brigham & Women's Hospital/Harvard Medical School, Boston. He detailed how cannabis impacts CB1 and CB2 receptors to interfere with pain signaling.