Skip to main content

© Sara Andreasson


© Sara Andreasson

A look at the different methods some patients use to take cannabis for medical reasons.

Many people connect cannabis with smoking joints. Indeed, cannabis cigarettes have long been used to treat asthma, as it was thought that inhaling cannabis opened the airway. Recent research has found that, while short-term exposure to cannabis can do this, the effects don’t last if cannabis is used over a six-to-eight-week period.

As medical use of cannabis has grown over the past three decades, and as people have moved away from smoking because of its harmful effects, other modes of administration have been developed. Only one, the oral spray, has gone through the medical approvals process, in the form of the cannabis-extract-based medicine Sativex. Other means, such as suppositories, are being investigated by scientists but have not yet been commercialised. We explore five methods below.


Inhalation method of taking medical cannabis

© Sara Andreasson

This method lets patients control the dose of cannabis because, inhaled, its effects begin almost immediately. The drug is taken into the lungs and quickly absorbed through the capillaries into the bloodstream. The effects last about four hours.

Smoking a joint is, however, dangerous – depositing tar and destroying cilia – not to mention illegal in many countries. It is also inefficient, as most of the cannabis is burnt. A bong or waterpipe can cool the smoke, which was thought to make it less irritating to the airway. However, the US Centers for Disease Control and Prevention says that this filtration method fails to remove any dangerous chemicals from the mixture.

A new means of inhalation is vaporisation (or “vaping”), which requires a piece of kit similar to a nebuliser. It heats the cannabis to 180–200°C, releasing the cannabinoids as a fine vapour to be inhaled. Some newer models of vaporiser have digital temperature controls to let patients control the heating more precisely (different cannabinoids vaporise at different temperatures). One of the authors of a US study published in 2007 said that “Using [carbon monoxide] as an indicator, there was virtually no exposure to harmful combustion products” using vaporisation. Dutch studies have also reported that it was a safe method of delivery.

Israeli company Syqe Medical is working on a cutting-edge inhaler, which is part-funded by the Israeli government. The device will enable metered doses of cannabis vapour to be produced, and it will be 3D-printable.

Oral spray

Oral spray version of medical cannabis

© Sara Andreasson

The British firm GW Pharmaceuticals developed a system in which cannabis plant-derived medicine is sprayed into the mouth. They say: “The oral spray method of delivery results in a slow rise in THC blood levels and also enables patients to adjust their dose. As a result, patients are typically able to separate the thresholds for symptom relief and intoxication, thus enabling them to obtain symptom relief without experiencing a high.”

The spray (known as Sativex in the UK) contains nearly equal amounts of the cannabinoids CBD and THC. CBD is thought to mitigate the psychoactive effects of THC. Patients tend to administer three to ten sprays over a 24-hour period. The company also points to the flexibility of a spray that can be carried around in a handbag and taken without water. In the US, the Food and Drug Administration has required the spray to include a dose counter, to reduce the potential for diversion for other purposes.


Edible medical cannabis

© Sara Andreasson

In Colorado (and some other US states), a dizzying array of cannabis edibles is now legally available, including sweets, cookies, ice creams, teas and even cannabis butter. However, absorbing cannabis through the gut is a slow process, taking an hour or more, so it is difficult for a patient to get their dose right.

Unlike when vaporised or smoked, cannabis that is ingested gets metabolised through the liver. The liver converts THC to another chemical, 11-hydroxy-THC, which is more psychoactive, so the effects (which some patients find unpleasant) can be stronger and take longer to wear off.

A recent study of edible cannabis products found wide variation in cannabidol (CBD) and delta-9-tetrahydrocannabinol (THC) levels, two of the major chemicals found in cannabis. This means that many products were mislabelled with regard to their contents.

On or under the skin

Medical cannabis on or under the skin

© Sara Andreasson

Cannabis can be applied topically for pain linked to inflammation, product manufacturers say, although general topical use is questionable, as it is unclear how well cannabinoids are absorbed through the skin.

A new generation of transdermal patches, gels and gel pens is being developed, containing an agent that manufacturers say can penetrate the skin. These products have not, however, been reviewed by the Food and Drug Administration in the US.


Taking medical cannabis as suppositories

© Sara Andreasson

Cannabis suppositories were first developed in the 1990s by Professor Mahmoud ElSohly, who runs the only legal cannabis farm for research purposes in the USA, at the University of Mississippi.

A 2001 study in rats, published in the Journal of Cannabis Therapeutics, concluded that rectal administration showed potential for therapy, and that effects could last for up to 12 hours. So far, no commercial products have been launched.

Buyer beware...

There is still much uncertainty around medical cannabis. In the US, for example, the rapidly emerging cannabis market lacks clear regulation. Many different products are available, some with little or no evidence to support their claims of efficacy. The US Food and Drug Administration recently tested medical cannabis products of all kinds (including some that were for dogs and cats) and found that six out of 18 had no cannabinoids in them at all – despite claims to the contrary.

This is not medical information, nor should it be interpreted as such. Using cannabis is illegal in many parts of the world, including the UK.


Return back to top of the page