You may be one of the many health care professionals who has been approached by patients looking for advice about CBD oil. It appears its everywhere these days, exploding on the alternative medicine scene over the last few years. You can pick up a bottle almost anywhere now, all the way from your local community pharmacy to newsagents. But what do we really know about CBD oil? Does the advice we have been giving differ from the advice we should be giving? This article was written to explore some of those themes and hopefully formulate a set of ideas we, as health care professionals can use when talking about CBD oil.

The Background

We spoke about some of the background surrounding cannabinoid therapy in the past article ‘Cannabis: what it is and why you need to know about it’ but let’s have a quick refresh. The active compounds found in the cannabis plant are known as cannabinoids, of these, the two largest constituents are THC and CBD, tetrahydro-cannabinol and cannabidiol respectively. THC is largely responsible for the psychoactive properties associated with recreational use of the plant and is the compound for which the legal restrictions are applied. CBD, on the other hand, has no psychoactive properties but is hypothesised to be one of the main ingredients responsible for the alleged medical benefits of cannabis. There are two endocannabinoid receptors found within the human body, these are named CB1 and CB2 and interestingly CBD has been found to have no agonist activity at these but antagonises CB1 receptors (P. Pacher et al 2006).

What can CBD be used for?

The use of cannabis for its non-psychoactive properties was recorded as early as the 3000BC when Chinese texts describe its use to treat pain and cramps (Mechoulam R 1986). But what ailments are people using it for today?

A quick google search would have you believe its beneficial for insomnia, multiple sclerosis, chronic pain, MSK symptoms, anxiety and depression and even acne. The anecdotal claims are too numerous to mention. But in today’s medical practise, anecdotes rarely make it into medical policy. There is however a body of evidence to support some of these medical claims, the BMJ even published a report called ‘Medicinal Cannabis:  The Evidence’ in 2015 to summarise what we currently know. Clinical human trials are lacking, however, there is evidence to suggest CBD has anti-inflammatory, neuroprotective and anti-oxidant properties. One study based on a rat model by D. C. Hammell et al 2016 found that topical CBD application had therapeutic potential for the treatment of arthritic pain and inflammation. So, we cannot dismiss claims by patients about benefits derived from using the product, but at the same time there is insufficient evidence to suggest we recommend it as a treatment option.

What advice should we be giving?

At present we haven’t untangled the complex pharmacology of each individual cannabinoid to differentiate by therapeutic potential, thus we don’t really know what isolated CBD is beneficial for. But the reality is that patients are self-treating with CBD oil, so what should we advise a patient who wants to try or is currently using CBD oil to treat arthritic pain for example?

Firstly, an open approach, taking into account the potential benefits and current evidence base but highlighting the lack of human trials to support its use. Also, encouragement that self-care is a fundamental of practice but works best when formulated with expert advice and the correct safety nets. At this point getting a full history of the reason for use, length of use, dosage and method of administration would be beneficial. That information together with an accurate patient history and drug history will help you consider a holistic answer tailored to the patient.

CBD oil is metabolised via the CYP 450 hepatic enzymes. As we know, these enzymes are responsible for the metabolism of around 70% of all drugs. In this case, CBD is a potent inhibitor of CYP3A4 and CYP2D6. This should feature in any discussion you have with patients around CBD oil. Although we don’t know the exact interactions in most cases and our knowledge of its enzymatic effects is still incomplete, theoretical understanding of the medicines which could be affected by this needs to be transmitted. Specifically, it has been found that CBD use increases warfarin and clobazam levels (Yamaori S et al 2012, Geffrey AL et al 2015).

Furthermore, CBD oil is currently sold as a food supplement with no MHRA herbal or medicinal authorisation. This is the legal reason why no medicinal claims can be attached to its use. But it has further implications. Having an MHRA authorisation requires the product to maintain highly reproducible percentage limits of stated drug content. This is stated in the BP monograph for each drug and is usually around 90-110%. This mean an Atorvastatin 10mg tablet would have to contain between 9-11mg of Atorvastatin for example. Obviously, this is essential to maintain therapeutic continuity. Not having an MHRA authorisation means this is not a requirement and so the quality control process is much less stringent. We can use unlicensed vitamin D supplements as an example here. One study by Garg S et al 2013 analysed 15 different preparations, only 8 of which were found to contain within 10% of the stated dose, with actual doses ranging from 8 to 201% of stated content. Moreover, another study found variation even within pills from the same packet ranging from 52-126% of the stated dose (Leblanc ES et al 2013). This possible variation in content adds another level of uncertainty around the use of CBD oil for therapeutic purposes which should be explained to the patient.

To sum up

Once you have discussed these points it’s the patient decision whether to use or not. As with the discussion around any medication, it’s an explanation of the risks Vs benefits for using a substance. Certain things would be red flags for extra caution, for example, high-risk drug interactions. But if the benefit is being derived and you can deduce no major issue, a managed approach to safe usage may be the best strategy.

Take these discussion case by case, even ask for more time to formulate an answer if you need to do some reading before feeling confident. But remember, there is no definitive guidance and the decision lies with the patient. Our role is to advise using our professional judgement and create a safe environment for the patient to explore their treatment options.

Autor: Matthew J Burgoyne MPharm


  1. C. Hammell et al. Transdermal cannabidiol reduces inflammation and pain-related behaviours in a rat model of arthritis. Eur J Pain. 2016 Jul; 20(6): 936–948. Available at:

Garg S, et al. J Nutr Health Aging 2013;17:158–61.

Geffrey Al et ala. Drug-drug interaction between clobazam and cannabidiol in children with refractory epilepsy. Epilepsia. 2015 Aug;56(8):1246-51. Available at:

Leblanc ES, et al. JAMA Intern Med 2013;173:585–6.

Mechoulam R. The pharmacohistory of cannabis sativa. In: Mechoulam R, editor. Cannabis as Therapeutic Agent. CRC Press; Boca Raton, FL: 1986. pp. 1–19

  1. Pacher, S. Batkai, G Kunos. The Endocannabinoid System as an Emerging Target of Pharmacotherapy. Pharmacol Rev. 2006 Sep; 58(3): 389–462. Available at:

Yamaori. S et al. Comparison in the in vitro inhibitory effects of major phytocannabinoids and polycyclic aromatic hydrocarbons contained in marijuana smoke on cytochrome P450 2C9 activity. Drug Metab Pharmacokinet. 2012;27(3):294-300. Available at:

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