Cannabis 101

What to know before prescribing cannabis

Rates of absorption and psychoactive effects vary widely between inhaled and ingested cannabis, according to comprehensive research in The Journal of the American Osteopathic Association.


For DOs managing the care of patients with chronic neuropathic or cancer pain, cannabis may be a viable treatment option. However, physicians are urged to counsel patients on the appropriate use of cannabis due to the possibility of varied and unpredictable effects, including schizophrenia and other psychiatric issues, according to comprehensive research in The Journal of the American Osteopathic Association.

Cannabis is currently classified in Schedule 1 of the Controlled Substances Act, a category for drugs such as heroin, but is legal for medicinal purposes in 30 states and the District of Columbia and recreational use in 8 states and the District of Columbia. Legalization of cannabis is under review in 12 additional states this year, leading to an increased need for physician awareness on how to counsel patients when prescribing cannabis.

“One of the biggest risks involves the potential aggravation or activation of latent psychiatric issues, such as schizophrenia,” says Jeramy Peters, DO, lead study author and psychiatrist at Oregon Health and Science University in Portland. “This is a special concern for young people in their late teens and early twenties, when their brains are still developing.”

Cannabis contains tetrahydrocannabinol (THC), which is responsible for the “high” people often experience, as well as cannabidiol (CBD), which is theorized to have antipsychotic and anxiolytic properties. Currently, CBD is being studied for its possible antiseizure and anti-inflammatory properties.

Cannabis strength

The strength of cannabis has been increasing over the past half century. During the 1960s, cannabis was typically about 1% to 5% THC by weight. Many strains available today range from 15% to 25% THC by weight, with some strains reaching 30% or higher.

The key to dosing cannabis safely for patients may be rooted in whether it is inhaled via a vaporizer or if it is ingested orally.  When inhaling, the user absorbs up to 33% of the total cannabinoids. If cannabis is smoked or vaped, about 25% of the cannabinoids present in herbal cannabis are absorbed. In both scenarios, intoxication occurs within minutes and lasts 2-4 hours.

By comparison, when ingested orally, THC is absorbed inconsistently. Users typically experience the effects of THC about 2 to 4 hours after ingestion, and its effects last for 6 to 8 hours, with a more intense and longer-lasting effect, increasing the possibility of overdose and negative effects.

‘Low and slow’

“The best advice we can give is start low and go slow,” says Walter Prozialeck, PhD, professor and chair of the Department of Pharmacology, Chicago College of Osteopathic Medicine at Midwestern University. He adds that more research is needed from the medical community to create specific protocols that physicians can use to better counsel patients.

Some longer-term effects associated with cannabis use include impaired memory, impaired concentration, and amotivation.

“It is very difficult to tell someone what effect they can expect without knowing the specifics of the product,” says Prozialeck. “How much THC is in the product, how it’s consumed—and, of course, the individual’s physiology—all play a role in determining their experience.”



  1. Michael Cunningham, DO Retired Residency Director, OU founder, Clinical Ass Prof, FP CORE member, Board Cert Family Medicine

    The National Academies of Science, Engineering, and Medicine 2017 published a 468 page report from the nations best in clinical researcher from John Hopkins, Columbia, Duke, Harvard, Vanderbilt, Univ of Pennsylvania, Michigan State, Univ of Cal, Univ of Pa and others on The Health Effects of Cannabis and Cannabinoids: “conclusive evidence regarding the short- and long-term health effects (harms and benefits) of cannabis use remains elusive. A lack of scientific research has resulted in a lack of information on the health implications of cannabis” “no accepted standards exist to help guide individuals as they make choices regarding the issues of it ” Physician you were warned in advance of it’s harm. Be prepared to explain what is meant by DNA fragmentation in the Hippocampus or the meaning of Schedule I classifications to a court of law .

    1. Micah Swanson

      Given this information, one has to ask why so many states are legalizing this substance. There appears to marginal evidence to support medical marijuana, so how can there be clinical guidelines? As far a marijuana in general, why are we in such a hurry to legalize it, especially in light of the escalating epidemic of opiate dependency in this country?
      In Ohio, 40% of job applicants test positive for drugs, and are largely unemployable by most industries. The social costs of marijuana usage is unknown, but surely include such factors as job productivity and impaired driving.
      As physicians we should not be prescribing this drug, and its medicinal dispensing should be purely investigational until benefits are clearly proven. Unfortunately, the state legislators and state medical boards have unleashed this problem on the medical profession and the public. The indications for medical marijuana need to be clearly evidenced based, and should not be otherwise prescribed. Both the AMA and the AOA have failed us in this regard.

  2. Dr. Eli S. Neiman, DO, FACN

    Bravo and very well written article.
    As of today, there is only very limited use for marijuana or any marijuana component for that matter. CBD oil (non-hallucinogenic marijuana component) as a third line agent for two very rare and catastrophic epilepsies (Dravet syndrome and Lennox Gastaut) looks promising. The dosing though of the CBD oil for children and adults is not yet known.
    In Europe, Sativex (mostly CBD with a small percent THC) has been helpful as a second or third line agent for spasticity and as a muscle relaxant for MS patients. I highly doubt though that it is better then Baclofen, Zanaflex or Flexeril for muscle spasm but time will tell.
    “First do no harm” is our motto.
    The number of narcotic, non-narcotic analgesics, anti-emetic medications and medications to treat neuropathic pain and cancer is very large and we have many treatment years of experience with these legal, FDA-approved medications. We do not know the THC content or absorption of what they are selling at the local dispensaries for there is no FDA regulation or oversight over what is being peddled out there.
    The kids and young adults behind the counters at many of these “dispensaries” are not PharmDs or pharmacists by any means. To put a patient in the hands of a college kid with often no training or degree and who just came back from touring with Phish is just not safe or ethical practice of medicine. Recent medical articles from the UK (where marijuana for medicinal and recreational use is legal in many places) state that they are having serious problems with the deluge of emergency room and psychiatric hospital visits for marijuana induced psychosis. The medical community in the UK now wants reconsideration of it use and its legality.
    Dr. Eli S. Neiman, DO, FACN
    Professor of Neurology Kansas City University
    Assistant Professor of Neurology, University of West Virginia.
    Assistant Professor Seton Hall University.

  3. Dr. Scott Gebhardt D.O.

    Interesting to note, both responses above mention “schizophrenia” as a concern. Yet there is this article out of the UK…
    Furthermore, there is this article about safety from the UK as well…
    As in all things medical, do your own research and then come to your own conclusions. An excellent start is to watch all 3 CNN documentaries with Dr. Sanjay Gupta on YouTube and then Dr. Ethan Russo M.D.

  4. Jack Goloff, D.O.

    Why does the title of the article read “prescribe.” We know as a schedule I, that is a non starter. I won’t participate in Florida’s program because the doctor must order the products for the patient online, specify amount, strength and dosage. If that is not prescription what is? Too risky.

  5. Laren Hightower, DO

    So to say that we have as or more effective treatments for chronic pain, with multiple studies backing such, among other conditions, that alternative treatments like medical marijuana guided by a knowledgeable physician are not beneficial is flawed. I can see the problem with either a patient not educating themselves thoroughly, or a nose-ringed-up dispensary clerk saying this or that to the public is definitely a big problem. However, even the American Pain Society and the American Academy of Pain Medicine rated 21 of 25 of their recommendations as “low-quality evidence” for long term use of opioid therapy. As you know, in 1996 they promoted opioid longterm use and look where that got us! The same ‘traditional medicine is always the best option’ that many physicians followed then is the same attitude I see in comments here. I get it, we should be wardens of public safety, but it’s because of the opioid epidemic that an alternative must be considered, not shunned. Also, with deductibles criminally high, if you were suffering with a chronic ailment as a patient, you’d seek out alternative treatments too. Educating ourselves as physicians to make our best recommendation to our patients is key. Yes, overdose on cannabis is real, but compare that to the number of overdoses, GIB’s, anaphylaxis, etc. of traditional medicine that we collectively prescribe daily – keep an open mind.

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