Cannabis
Alcohol Pharmacology Effects on driving Measuring alcohol Cannabis Pharmacology Effects on driving Stimulants Pharmacology Effects on driving Prescribed Drugs Which ones matter? The Inexperienced Driver Learning to drive The impact of inexperience Publications Articles published by us Links Welcome Page Contact us		Cannabis Cannabis (marijuana) is a mixture of the dried flowering tops and leaves from the plant Cannabis sativa. Like most natural materials derived from plants, it is a variable and complex mixture of many chemical compounds, some of which are pharmacologically active. Marijuana contains more than 400 chemicals. Approximately 60 are called "cannabinoids" and are found in no other plant. The most active of these compounds is delta-9-tetrahydrocannabinol, which is abbreviated to delta-9-THC or more simply THC. Varying proportions of other cannabinoids, mainly cannabidiol (CBD) and cannabinol (CBN), are also present, sometimes in significant quantities that cause effects of their own. CBD is not psychoactive but has significant other pharmacological activity. Cannabis has been variously classified as a narcotic, a sedative and as a hallucinogen, but it is actually in a class of its own. It acts on specific receptors that are found in the parts of the brain associated with thinking. When marijuana is smoked, THC and other cannabinoids present in the smoke enter the circulation within seconds and are rapidly delivered via the blood stream to the brain. Peak blood levels appear about the time smoking is finished. The cannabinoids are then distributed rapidly throughout the body. THC is mostly metabolised to an inactive metabolite, 11-nor-delta-9-tetrahydocannabinol-carboxyllic acid (THC-COOH). Unlike many other substances, peak levels of THC occur immediately after smoking, when the person feels subjectively affected ("stoned"), but peak impairment occurs about an hour later, when levels have fallen to about 10% of peak level in blood. Cannabinoids are highly fat soluble, and disappear rapidly in fatty tissues from which they are very slowly released back into the blood stream. They are then slowly converted to the inactive soluble form and excreted. Complete elimination of a single dose may take up to 30 days.
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