Doctors wary of cannabis as a medicine

Doctors seem wary of prescribing approved cannabis products ahead of substantial clinical trials, and patients are missing out, writes Dr Karen Oldfield

Awareness of cannabis as a medicinal product has been rising significantly. Doctors in Aotearoa New Zealand report more patients are asking about the use of cannabis as a medicine—and patients report they’re comfortable discussing the drug with their doctors.

But there are still obstacles facing those who want to use cannabis for medicinal purposes. My research found many patients who had spoken to their doctor about it did not receive a prescription.

In a survey of 153 neurology patients, 45 (29 percent) said they’d discussed medicinal cannabis use with their GP but just seven were prescribed a cannabis product.

The results were similar when patients raised the drug’s use with their specialist: of 43 patients who had discussed it, just nine were prescribed a product.

With prescriptions hard to come by, one in three were instead using illicit or recreational cannabis, either smoking or ingesting products to treat symptoms.

Evidence suggests there is a significant number of people who use illegally acquired cannabis to meet their medical needs, with many reporting a reduction in symptoms.

Reluctance to prescribe

Separate survey research with GPs and doctors working in specialty areas found medical professionals can be reluctant to prescribe medicinal cannabis, mainly due to the lack of good quality evidence for efficacy and dosing regimens.

Of 76 GPs surveyed, just over half had been asked to prescribe cannabis in the past 12 months. Two-thirds of those didn’t give the patient a prescription. The most common reason for declining the request was an “insufficient evidence base” to support the product’s use.

Poor understanding by doctors of the rules for prescribing cannabis is another barrier patients can face.

These rules have changed in the past five years. When I started my PhD, only neurologists could prescribe the cannabis product Sativex, and only for spasticity caused by multiple sclerosis. By the end of my PhD, any doctor could prescribe this drug for any reason, as well as products meeting the standards of the Medicinal Cannabis Scheme (other products must still be approved by the Ministry of Health before being prescribed).

In 2017, cannabidiol (CBD) was also removed from the controlled drugs register and could be prescribed by doctors, although this wasn’t widely known.

Clinical trials needed

Lack of medical evidence makes it difficult for doctors and patients to have an informed conversation about whether medicinal cannabis is the right choice.

Information on a product’s safety and efficacy is vital to understanding its benefits and side effects. This information can only be sourced through rigorous testing of the products themselves, and clinical studies of safety and efficacy.

Ideally, there needs to be the ability to fund and undertake clinical trials of New Zealand-based products. Most doctors surveyed said they would prescribe a funded cannabis-based product that was backed by evidence from clinical trials.

Arranging and funding trials has historically been quite difficult, mainly due to cost and access to products. One solution could be asking companies applying for their products to be accepted under the Medicinal Cannabis Scheme to provide product samples for medical research.

Independent testing of products is also needed to detect contaminants. Evidence from other markets where medicinal cannabis is available has found contaminants across the range of cannabinoid-based products. These contaminants included microbes, solvents, pesticides and adulterants.

Labelling inaccuracies have also been found. Labelling accuracy of products in the markets that I compared in my research ranged from 17 to about 86 percent.

In my current work at the Medical Research Institute of New Zealand, I’m planning to run clinical trials on New Zealand-made medicinal cannabis products in order to source the safety information doctors and patients need to feel comfortable prescribing and using these products.