This review has suggested that cannabinoids may be useful in the treatment of many disorders. The most likely applications for cannabinoid agonists are for the treatment of loss of appetite, pain, anxiety, vomiting, nausea and epilepsy. The most likely applications for cannabinoid antagonists may be for anxiety, schizophrenia, spasticity, and dystonia. It is difficult to formulate an hypothesis concerning the potential treatment of depression, bipolar disorder and alcohol dependence since very little work has been done with these disorders at this point of time.
Another possibility is that mixtures of agonists and antagonists might be useful since it has been demonstrated that CBD attenuates the psychoactivity of THC (Karniol and Carlini, 1973; Karniol et al., 1974). At present, GW Pharmacueticals has launched a series of animal and human research studies, using extracts from cloned cannabis plants which have different amounts of cannabinoids in them to test this hypothesis using a sublingual route of administration.
In addition, the recent Institute of Medicine report (Watson et al., 2000) recommended:
Clinical trials of marijuana use for medical purposes should be conducted under the following limited circumstances: trials should involve only short-term use
(less than six months), should be conducted in patients with conditions for which there is reasonable expectation of efficacy, should be approved by institutional review boards, and should collect data about efficacy.
Research with smoked marijuana could reveal differential effects of the multiple cannabinoids in the plant as compared with the effects of testing pure compounds. At present, however, it is unlikely this type of research will be done, since a supply of cannabis with different ratios of cannabinoids is not readily available to the research community even though cloned plant extracts have been developed.
Since the discovery of the CB1 and CB2 receptors and endogenous cannabinoid ligands, the potential for development of synthetic drugs seems possible. Several drugs seem to have some potential and are under intensive study, as discussed above: the CB1 and CB2 receptor anatagonist SR141716 (Sanofi-Synthelabo), HU-211 (Pharmos) and CT-3 (Atlantic Pharmaceuticals).
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