Cannabis oil caution with common rheumatology drugs

Cannabidiol (CBD) oil has the potential to interact with several drugs frequently prescribed by rheumatologists, finds new research which highlights the importance of taking comprehensive drug histories.

In a letter published in Rheumatology, rheumatologist Dr Taryn Youngstein from Hammersmith Hospital, London, and colleagues said that although evidence for the benefits of CBD was ‘minimal’ its anti-inflammatory action made it a potentially attractive addition to the current range of analgesics available to patients with rheumatic diseases and chronic pain disorders.

They noted that patients were increasingly asking for information on the safety of CBD oil yet there was currently no published literature on the topic.

But by scanning several drug databases they identified 15 rheumatology drugs that had the potential to interact with CBD, with the most important potential interaction occurring between corticosteroids and CBD.

“Hydrocortisone and prednisolone are both metabolized by the cytochrome P450 enzyme CYP3A. Cannabidiols, particularly CBD, are potent inhibitors of CYP3A, therefore concomitant use may decrease glucocorticoid clearance and increase risk of systemic CS side-effects,” they wrote.

Other drugs that could potentially interact with CBD included celecoxib, citalopram, fluoxetine, mirtazapine, paroxetine, sertraline, tofacitinib and tramadol.

The research team noted that Janus kinase inhibitors differed in their interaction profiles because of the way they were metabolised. For example, tofacitinib was predominantly metabolised in the liver by  CYP3A4 and CYP2C19 both of which inhibits CBD.

In contrast, baricitinib was almost exclusively cleared by the kidneys and had minimal mediation by CYP3A4, resulting in a favourable profile without significant predicted interactions.

No predictable interactions were seen with the majority of DMARDs or biologics, including methotrexate, hydroxychloroquine, sulphasalazine, mycophenolate motefil, mesalazine, adalimumab, etanercept, abatacept, infliximab, or rituximab.

“We recommend caution with the listed medications in patients using CBD oil, particularly as established standards for safe production and a fixed dosage unit are lacking,” the authors concluded.

Their findings highlighted the importance of taking comprehensive drug histories from patients, they added.

Meanwhile, NICE, the body that oversees prescribing guidelines for the NHS in the UK, has published new recommendations on the prescribing of medical cannabis. These include the use of nabilone for nausea in chemotherapy patients who haven’t responded to other treatments. The guidelines are being consulted on until the beginning of September.

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