GW Pharmaceutical of the UK, which is fast becoming the world leader in research into the therapeutic benefits of cannabis, has announced that it is to begin Phase I trials of a new weight loss drug which is derived from cannabis. Cannabis contains tetrahydrocannabinol (THC) which activates the CB1 and CB2 receptors to boost appetite. However, another substance known as tetrahydrocannabivarin (THCV) is also present and this has the opposite effect. If the THCV is isolated, this can be used as the basis for a medication which may be able to switch off the appetite. Clearly, this may have serious undesirable side effects so the drug will have to go through years of thorough tests before it is available to prescribe. As soon as we have some more information, we will post it here.