Dr Jürgen Fleisch provides his insights on prescribing medicinal cannabis

There is a place for cannabinoids in the therapeutic toolbox. So how should they be prescribed? Dr Jürgen Fleisch  highlights prescribing realities and strategies to improve patient safety, dispels some myths, and aims to encourage self-driven inquiry. He has prescribed cannabinoids, mainly for patients with cancer, since he started working in Holland ten years ago.

Do you have any advice for doctors starting out prescribing?

My advice for clinicians who are starting to prescribe cannabinoids is to stick to specific indications where there is a solid foundation of evidence for its use, e.g. multiple sclerosis, patients experiencing central neuropathic pain, or cancer patients. This allows us to gain experience with the effects of this medication in a specific patient population. Recreational cannabis users are, in my opinion, not a good patient category to start with. They may put considerable pressure on the clinician to prescribe for dubious indications.

Can you describe a typical patient who you would prescribe products containing cannabinoids?

There are two typical types of patients where I would initiate cannabinoid therapeutics. These are in patients with:

• advanced cancer experiencing loss of appetite and possibly nausea and vomiting. Often many other medications have been tried before.
• central neuropathic pain (after unsuccessful trials of more common medications).

Prescribing cannabinoid therapeutics

How is prescribing cannabinoid therapeutics different to prescribing other medicines?

They are like any other medicine. However, many patients will have an opinion about cannabis [and cannabinoid products]. For some it has a rather negative connotation as being a substance of abuse.

What are the key benefits of cannabinoids as a therapeutic product?

There are three main advantages of cannabinoid therapeutics in general over other medicines used in my field of pain medicine, these include that:

• there are analgesic effects on neuropathic pain syndromes and, depending on the medicine type, anti-emetic and appetite stimulating effects. This is especially important for cancer patients with pain.
• there are no known organ damaging side effects in the adult patient. As compared to, for example, those linked with using NSAID’s.
• some cannabis flos variants have a soothing effect, which some patients greatly appreciate.

What do you think are prescribing practices that improve patient outcomes?

For patients with no experience using cannabinoid products, the possible psychological side effects can be distressing. In order to avoid this we advise patients’ to start with low dosage and use the medicine in a quiet and relaxing environment.

In our experience, it is advantageous to prescribe cannabis flos as an inhalational agent, administered by vaporization, as it creates more rapid analgesic effects and has a more reliable absorption profile.

Are there any special considerations you make when prescribing a ‘herbal’ medicine (cannabis flos)?

With cannabis flos, the prescribing clinician needs to be aware that in many countries the standards are different with respect to ‘regular’ medicines: concerning the quality control of the active ingredient, and toxicological contamination.

Therapeutic use of cannabinoids

Medicinal cannabis is a term used to describe the use of cannabis to treat or manage illness. It hails from a time when the products used where typically marijuana and patients smoked joints. Since that time, there have been major developments in cultivation techniques, product quality and controls. Today, the sympathetic regulatory environment favours standardised products (e.g., Bedrocan cannabis flos, Sativex) and safer modes of administration (sublingual, oral and vaporization). A prescriber-pharmacy model now offers patients better communication of risks and benefits, and the safety of health professional oversight. Standardised products and clinical research means plant-based products are closer to achieving full medicine registration. The use of the term ‘medicinal cannabis’ in these circumstances seems redundant.

In this article, we talk about the therapeutic use of cannabinoids. The class of medicines containing cannabinoids (e.g., THC and CBD) and other chemical compounds secreted by cannabis plant (e.g., terpenes) that are intended to be used in, or on human beings for a therapeutic purpose. This change in terminology from ‘medicinal cannabis’ to ‘cannabinoid therapeutics’ reflects our knowledge and understanding of the endocannabinoid system, the cannabinoid receptors, endogenous (human) cannabinoids, and exogenous (plant) cannabinoids.

Using cannabis flos originating from controlled producers means patients are assured there is no biological or toxicological contamination. In the Netherlands cannabis flos is produced under strict quality conditions by the government licenced company Bedrocan.

Administration by vaporization

Aside from eliminating the harms from smoking, what are the benefits of administration by vaporization?

With vaporization cannabis flos is heated to a specific temperature without burning it. Cannabinoids and terpenes are released in a vapour which is directly inhaled.

There are three main advantages of administration by vaporization is that it:

• allows for exact dosing,
• leads to a rapid effect, and
• avoids the disadvantages of smoking (i.e., no tar, ammonia, carbon monoxide).

What do patients say about the administration of cannabis flos by vaporization?

Using vaporized cannabis flos is the preferred means of use by most patients, especially when compared with an oral application. This is due to the more rapid effect by inhalation.

For some years the vaporizers where reimbursed by Dutch health insurance, thereby eliminating the threshold of a financial burden for the patient.

Patient considerations

Thinking about a first consultation with a patient, how do you start a conversation about cannabinoid therapeutics?

There are two types of discussion around the use of cannabinoids:

The elderly, cannabis naive patient

An elderly cancer patient may be hesitant to use cannabis as a medication. This likely is related to prejudices about cannabis being a product for ‘recreational’ use. With these patients, I rarely discuss the use of these medicines during a first consult. If the patient is eligible and several other therapies did not provide sufficient pain relief, I then mention cannabinoid therapeutics as a possible option. This allows the patient and his/her family to contemplate that treatment option until the next appointment.

The experienced patient

There may be patients who have extensive experience using cannabis recreationally. They may be actively looking into cannabinoid therapeutics as a potential adjunct to their pain therapy. These patients emphasise the ineffectiveness or side effects of other therapies, and may push clinicians towards prescribing a cannabis product. With these patients the topic must be discussed fully during a first consult. The main question during this consult is are they at all eligible to receive cannabinoid products.

Are you aware of patients experiencing interactions with cannabinoid therapeutics and other medicines?

Indeed, we do see patients who experience drug interactions using cannabinoids alongside other CNS depressant medications (e.g. opioids).

Sedative effects can be enhanced especially in the geriatric population. Severe drowsiness and hallucinations can also be provoked.

Aside from drug interactions, the smoking of cannabis is related to an increased risk of myocardial infarction and stroke. Cannabis as a trigger of myocardial infarction is plausible, given its cardio-stimulatory effects, which may cause ischemia in susceptible hearts. Carboxy-hemoglobinemia from the smoking of cannabis may also contribute to ischemia. Smoking is never recommended.

Do you encounter diversion for misuse or the abuse of cannabinoids? How do you identify this issue in your practice?

During the period when Dutch health insurers widely reimbursed medicinal cannabis, we had frequent discussions with patients, best described as ‘recreational users’, about their eligibility.

Patients of this group, who were already using large amounts of cannabis, were requesting access for rather dubious indications. Some patients were seeing it as a cheap way to get a ‘recreational drug’ which they were already abusing.

How do you deal with diversion for misuse or abuse in your practice?

This patient group can be quite challenging. They may put pressure on clinicians to prescribe cannabinoids as the only means to relieve their pain. Mentioning misuse and abuse can provoke abrupt reactions.

Clinicians should be coherent in prescribing cannabinoids only for indications with enough evidence for beneficial effects (e.g. analgesic for neuropathic pain, appetite stimulation etc). Misuse and abuse should be discussed openly if they become apparent.