Cannabinoids in clinical practice

Cannabinoids in clinical practice

Williamson EM, Evans FJ
Drugs 2000 Dec; 60(6):1303-14

Centre for Pharmacognosy, The School of Pharmacy, University of London, England.

Cannabis has a potential for clinical use often obscured by unreliable and purely anecdotal reports.The most important natural cannabinoid is the psychoactive tetrahydrocannabinol (delta9-THC);others include cannabidiol (CBD) and cannabigerol (CBG). Not all the observed effects can beascribed to THC, and the other constituents may also modulate its action; for example CBDreduces anxiety induced by THC.

A standardised extract of the herb may be therefore be morebeneficial in practice and clinical trial protocols have been drawn up to assess this. The mechanismof action is still not fully understood, although cannabinoid receptors have been cloned and naturalligands identified. Cannabis is frequently used by patients with multiple sclerosis (MS) for musclespasm and pain, and in an experimental model of MS low doses of cannabinoids alleviated tremor.Most of the controlled studies have been carried out with THC rather than cannabis herb and so donot mimic the usual clincal situation. Small clinical studies have confirmed the usefulness of THC asan analgesic; CBD and CBG also have analgesic and antiinflammatory effects, indicating that thereis scope for developing drugs which do not have the psychoactive properties of THC.

Patientstaking the synthetic derivative nabilone for neurogenic pain actually preferred cannabis herb andreported that it relieved not only pain but the associated depression and anxiety. Cannabinoids areeffective in chemotherapy-induced emesis and nabilone has been licensed for this use for severalyears. Currently, the synthetic cannabinoid HU211 is undergoing trials as a protective agent afterbrain trauma. Anecdotal reports of cannabis use include case studies in migraine and Tourette'ssyndrome, and as a treatment for asthma and glaucoma. Apart from the smoking aspect, the safetyprofile of cannabis is fairly good.

However, adverse reactions include panic or anxiety attacks,which are worse in the elderly and in women, and less likely in children. Although psychosis hasbeen cited as a consequence of cannabis use, an examination of psychiatric hospital admissionsfound no evidence of this, however, it may exacerbate existing symptoms. The relatively slowelimination from the body of the cannabinoids has safety implications for cognitive tasks, especiallydriving and operating machinery; although driving impairment with cannabis is only moderate, thereis a significant interaction with alcohol. Natural materials are highly variable and multiplecomponents need to be standardised to ensure reproducible effects. Pure natural and syntheticcompounds do not have these disadvantages but may not have the overall therapeutic effect of theherb.

Cancer References: ACS : American Cancer Society

Depression References: MEDLINEplus: Depression

Diabetes References: American Diabetes Association

Medical References: National Library of Medicine - PubMed

Pancreatic Disease References: MEDLINEplus: Pancreatic Diseases