To conclude, no analgesic or antihyperalgesic activity of cannabis extract was found in the experiments. Moreover, the results even point to the development of a hyperalgesic state under cannabinoids. Together with previous data, the current results suggest that cannabinoids are not effective analgesics for the treatment of acute nociceptive pain in humans.

Delta-9-tetrahydrocannabinol (THC) is increasingly used for the long-term treatment of nausea, vomiting, cachexia, and chronic pain. Recent reports, however, have indicated an increased risk of myocardial infarction and thromboangiitis obliterans after THC intake. Blood platelets have an essential role in the pathogenesis of these two diseases, but it is unclear whether platelets are potential target cells for cannabinoids. We investigated the effects of THC on human platelets and the expression of cannabinoid receptors on their cell membranes in this in vitro study. The effects of THC (final concentrations 10(-7) to 10(-5) M) on the expression of activated platelet fibrinogen receptor (glycoprotein IIb-IIIa) and P selectin were characterized by flow cytometry. Western blotting was performed with platelet membrane preparations to determine the surface expression of cannabinoid receptors on human platelets. THC increased the expression of glycoprotein IIb-IIIa and P selectin on human platelets in a concentration-dependent manner. The two known cannabinoid receptors (CB(1) and CB(2)) were both detected on the cell membrane of human platelets. Our functional results may suggest a receptor-dependent pathway of THC-induced platelet activation. However, further in vivo studies are warranted to evaluate the role of cannabinoid receptors in mediating the demonstrated procoagulatory effect of THC.

Cannabis sativa is one of the oldest crops cultivated for the production of fibers and for medical and recreational purposes. Since the detection of specific cannabinoid receptors and their physiological ligands, the understanding of the cannabinoid signalling system has increased, leading to a recent resurgence of interest in its medicinal properties. In animal studies, cannabinoids exerted significant analgesic and antihyperalgesic effects, suggesting the usefulness of cannabinoids in pain conditions. However, in human experimental or clinical trials, no convincing reduction of acute pain was observed. In contrast, in chronic pain and (painful) spasticity, an increasing number of randomized, double-blind, placebo-controlled studies have shown some efficacy of cannabinoids. Besides pain, cannabinoids consistently improved mood, sleep and coping. Although cannabinoids are not first-line analgesics, they may be useful adjuvants for some special groups of patients.

In many European countries the use of opioids for long-term treatment of nonmalignant pain has dramatically increased during the last decade in order to improve the patient's quality of life, to allow an active social life and the return to work. In modern society, driving is regarded as an essential activity of daily living. Since opioids are centrally acting drugs that may interfere with the ability of safely driving a motor vehicle, the question arises of whether or not and on which conditions patients under continuous opioid medication may be considered fit to drive. In this article the evidence from recent studies of opioid effects on driving ability of patients is reviewed. Based on these data, the prerequisites and restrictions for driving under chronic opioid medication are outlined and practical guidelines are proposed.