What is cannabis oil and how does it work?

Your questions about the medical use of cannabis oil answered

Ian Sample


In Brazil cannabis oil is given to children with microcephaly. Photograph: Saulo Santiago for the Guardian 

What is cannabis oil?

Cannabis oils are extracts from cannabis plants. Unprocessed, they contain the same 100 or so active ingredients as the plants, but the balance of compounds depends on the specific plants the oil comes from. The two main active substances in cannabis plants are cannabidiol, or CBD, and delta-9 tetrahydrocannabinol, or THC. Oil extracted from hemp plants can contain a lot of CBD, while oil from skunk plants will contain far more THC. THC produces the high that recreational cannabis users seek, while oils for medical use contain mostly CBD.

How is it different to cannabis?

Other forms of cannabis are solid and are usually sold either as resin or dried plant material. In commercially-produced medical cannabis oils, the concentrations of CBD and THC tend to be well-controlled, which makes it easy to calculate doses.

Does it work as a medicine?

CBD is an anticonvulsant, and some other compounds in the plant, including THC and cannabidivarin, may be too. There is good evidence from clinical trials in the US and Europe that pharmaceutical preparations of CBD can treat two severe forms of childhood epilepsy known as Dravet syndrome and Lennox-Gastaut syndrome. Both forms of epilepsy often fail to improve with existing epilepsy drugs. CBD is generally considered safe, but some trials have reported side effects including dry mouth, lightheadedness and altered liver enzyme activity.

Don’t we already have cannabis-based drugs?

Four drugs based on cannabis compounds are already on the market in Europe. Among them are Nabilone, a synthetic compound that mimics THC, is prescribed for nausea and vomiting caused by chemotherapy, and Sativex, an oil that contains equal parts THC and CBD, is used to treat muscle spasms in multiple sclerosis. Both contain too much THC to administer to children. “The only medicines that are approved in the UK would get children stoned,” said David Nutt, professor of neuropsychopharmacology at Imperial College, London.

Is cannabis oil illegal?

Cannabis oil can only be sold legally in Britain if it contains less than 0.05% THC. But the nation’s medicines regulator, the MHRA, announced recently that even pure CBD could not be sold as a medicine without first going through the usual clinical testing and safety checks required for all new medicines. This month, the US Food and Drug Administration will consider the approval of Epidiolex, a CBD-based medicine from GW Pharmaceuticals, which has completed such clinical trials. The European Medicines Agency (EMA) will rule on the drug early next year. If the EMA approves Epidiolex, it could be available to prescribe to named patients in Britain next year, Brexit notwithstanding.

Is it legal in other countries?

Europe is a patchwork of cannabis legislation. In the Netherlands, doctors can prescribe cannabis and cannabis preparations for symptoms caused by multiple sclerosis, HIV/AIDS, cancer, long-term pain and the tics associated with Tourette’s syndrome. Other European nations are following suit. In the US, at least 29 states allow medical uses of cannabis, and earlier this year, California became the eighth state to permit recreational use of the drug, too.