Prescribing any sort of medicine requires guidance in the form of rigorous scientific data. In general, this takes two forms: clinical trials, and clinical case studies. The first relies on experimentation in the lab, while the second relies on the real-world experiences of doctors. While effective, this process is time-consuming and often produces conflicting results. This can be extremely frustrating for patients who have exhausted all current options in their search for relief. It may even lead some patients to try untested and unregulated therapies, with potentially disastrous results.
A recent survey of American physicians found that 89.5% felt unqualified to prescribe medical cannabis; even worse, only 35.3% felt qualified to answer a patient’s questions on the subject. This is due in large part to a lack of education and experience. The same survey shows only 9% of medical schools include cannabis in their curricula. However, many European countries have been prescribing cannabis for quite some time. In the spirit of sharing their experience, a pair of experts have recently published a review in the European Journal of Internal Medicine (EJINME(, summarizing existing data regarding the use of medical cannabis, and offering guidelines for its prescription.
The article begins with a brief review of cannabinoid pharmacology, contrasting the uses of THC and CBD. For example, THC has proven benefits for chronic pain relief, insomnia, and loss of appetite, while CBD has been used for its anti-anxiety and anti-psychotic effects. One advantage of medical cannabis, then, is that patients can use a single medication for multiple symptoms. This reduces the number of medications a patient needs to take, reducing the cost for the patient and avoiding the potential of adverse drug interactions.
The authors also take a moment to discuss and classify different strains of the cannabis plant. Each chemovar, the correct technical term for a strain, falls into one of three categories. Type I chemovars predominantly produce THC, Type II chemovars are an even mix of THC and CBD, and Type III chemovars contain mostly CBD. In recent years, there has been a shift in demand in North America for the Type II and III chemovars.
DOSAGE DETERMINATION AND METHODS OF ADMINISTRATION
Next, they offer strategies for ensuring patients receive the proper dose. Their advice is to “start low, go slow, stay low”. By starting with lower doses, a patient can avoid many of the adverse side effects of cannabis. Further, this strategy helps patients who are new to cannabis develop a tolerance. Interestingly, this tolerance only extends to the profile of adverse effects, and not the therapeutic effects of cannabis. This is in contrast to opioids, which lose their effectiveness over time, requiring a patient to take more to get the same effect.
A potential complicating factor for the above advice is the method of administration. For example, smoking or vaporizing of herbal cannabis can produce smoke/vapors with highly variable quantities of cannabinoids. Physiological and behavioral factors, such as lung volume and breath holding, also affect cannabinoid absorption. Oral doses have less variability, but the time to onset is longer, and may not be useful for immediate symptom relief. The authors note that the effectiveness of medical cannabis varies widely from person to person, so they suggest that patients keep a “symptom inventory” to track each dose and their response.
In addition to their general advice, the authors provide specific dosage recommendations for patients as well. For new patients, they suggest starting off with 2.5 mg THC, administered just before bedtime. This helps patients develop a tolerance and avoid adverse events. While not explicitly stated, it also helps patients become familiar with their new medication in a safe environment. If this dose is well tolerated, the patient can increase their intake by 1.25-2.5 mg over the course of several days, until symptomatic relief is achieved.
The potency of chemovars varies greatly, as does the dose achieved by smoking/vaporization, so it’s important for each patient to pay attention to their symptoms relative to intake. To achieve the correct dose, they suggest starting with a single puff, then waiting fifteen minutes before taking another, if necessary. The authors note that the therapeutic effects are separate from the euphoric effects exerted by THC. This means that any euphoric effects are not a signal of therapeutic relief, and should not be viewed as such.
Once a patient has determined their optimal dose and developed a tolerance, it may be possible for patients to begin using during the day. For daytime use, oral administration may be a better option. The effects are much longer lasting, and it’s easier to measure each dose. Again, the advice is to go slow, starting with an oral dose of 2.5 mg once a day. After a few days, a second dose may be added in the evening. Dosing frequency should not exceed three times per day, with a maximum daily total of 15 mg THC per day. Going beyond this threshold increases the likelihood of adverse events, but will not increase any therapeutic effects.
ADVERSE EVENTS, DRUG INTERACTIONS, AND SPECIAL CASES
Finally, they review the profile of adverse events associated with medical cannabis and known drug interactions. Most of the adverse events occur when beginning treatment, and disappear over time. The profile of adverse effects is quite mild compared to many prescription drugs, and there have been no known cases of death by overdose. To date, there is little research studying interactions between cannabis and other prescription drugs, but the authors state that it has so far proven safe to use with other medications.
There are certain groups of patients that require extra consideration before prescribing cannabis. These include pediatric and elderly patients, and also those suffering from chronic pain, opioid addiction, cancer, Epilepsy, and Parkinson’s disease. In each case, they discuss the potential benefits and drawbacks for use in each situation. Considerations of this type may be critical in choosing the best treatment option for each patient.
While guidelines of this sort cannot make up for the lack of cannabis education in American medical schools, it is at least a starting point for those physicians in areas where cannabis is an option. Though brief, this review is quite thorough, and also provides links to other useful resources for practicing medical professionals. Furthermore, guidelines like this can help physicians and the general public to view cannabis as a legitimate form of therapy. As more clinical trials are completed and more cannabis-based medicines hit the market, American doctors will start to catch up to their European counterparts.
*As always, this summary is not intended as a substitute for seeking medical advice from a licensed medical professional, and SHOULD NOT be used in this way.