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Medical cannabis could appear on the illegal market and lead to a crisis similar to the misuse of opioid prescriptions, a group of pain medicine consultants have warned.
The warning was laid out in a letter to The Times
published on 26 October 2018, which was signed by 166 hospital consultants, led by Rajesh Munglani, an honorary consultant in pain medicine at St Thomas’ Hospital in London.
The doctors say a change in the law that will see medical cannabis rescheduled and available on prescription from 1 November 2018 could make it “difficult to deny cannabis prescriptions to patients in pain who might be coerced into diverting cannabis into the community where it will remain illegal and have street value”. The letter references the opioid crisis and warns that a similar scenario could develop around the misuse of legal medical cannabis.
The consultants say they support a change in the law to encourage cannabis research, but that claims that cannabis products containing tetrahydrocannabinol are an effective treatment for chronic pain are, they argue, not currently supported by evidence. Moreover, they add, the use of such products “may be associated with significant long-term adverse cognitive and mental-health detriment”.
Similar views on the use of cannabis for chronic pain were recently expressed by the Faculty of Pain Medicine of the Royal College of Anaesthetists.
In a position statement published in October 2018, the Faculty quotes the March 2018 Cochrane review ‘Cannabisâ€based medicines for chronic neuropathic pain in adults’
, which reported “a lack of good evidence that any cannabis-derived product works for any chronic neuropathic pain”. The Faculty went on to say that cannabinoids should only be used for pain management if “conventional interventions” have failed.
Ash Soni, president of the Royal Pharmaceutical Society (RPS), said that the legislative change has been “very specific in the treatment areas where medical cannabis can be used”.
“It will only be able to be prescribed in identified areas, by specialists using guidelines to support their decision making,” he said.
Soni acknowledged “valid concern” about the evidence base for medical cannabis, but said “this limited use will develop the evidence base as part of the outcome”.
In response to concerns about diversion of legal medical cannabis, Soni said that “the restrictions placed should ensure there is not widespread use [of the products] and therefore the risk of diversion is less than we have seen from the use of opiates — particularly as patients receiving this treatment will require regular specialist review to ensure they are benefitting from it”.
“The RPS reaffirms its support for the legislative change, which will enable further research to determine the most appropriate areas to use these drugs. This will ensure they are only used where the evidence justifies it,” he added.
