Cannabis

Marijuana is the most commonly used of all of the illicit drugs and the most frequently detected substance in workplace drug testing conducted by Medvet Laboratories. In Australia 33.6% of people have tried marijuana at least once in their lives, and 16.4% are daily users of the drug. The 30-39 year old age group were more likely than those in other age groups to use marijuana every day. One in ten recent users admitted to using cannabis in the workplace.

Cannabinoids are derived from the plant Cannabis Sativa. Marijuana is the dried leaves, flowers and stem of the plant. Hashish consists mainly of the resin from the flower clusters on the female plant. It is usually either smoked or ingested mixed or cooked in with food or liquids such as tea.

Other common names used for cannabinoids are marijuana, dope, pot, herb, weed, grass, ganja, mary jane and hash.

The main active ingredient in cannabis that produces a 'high' is called delta-9 tetrahydrocannabinol, or more commonly, THC.(9)

Acute Effects

In common with other psychoactive drugs, the effects of cannabis depend on the dose, individual and setting.

The most common effects include:

• disinhibition
• heightened visual and auditory perceptions
• altered time perception
• concentration - general difficulty and a tendency to focus awareness on a particular activity

Negative Acute Effects

There can also be negative acute effects such as:

• anxiety and panic
• paranoia
• visual or auditory hallucinations
• impaired coordination

Long-term effects

Regular and continued use of cannabis may cause or contribute to a number of health problems, including:

• Respiratory difficulties - cannabis smoke contains many substances which irritate the airways, and many smokers tend to hold the smoke in for longer, which aggravates respiratory problems
• increased risk of cancers of the lung, mouth, throat and tongue - cannabis smoke contains numerous carcinogens

• cannabis dependence syndrome: characterized by a variety of cognitive, physical and behavioural symptoms, such as an inability to control use, continued use despite problems, withdrawal and tolerance

• increased risk of psychotic symptoms resulting in anxiety, panic reactions or paranoia.
• cannabis dependence reduced fertility in both men and women

A number of other problems can be caused or made worse by involvement with cannabis:

• decreased motivation or energy to accomplish tasks
• poor school or work performance
• family and relationship problems
• legal problems - cannabis and its use are illegal, so users may come to the attention of police, and receive fines and criminal convictions

Tolerance and Dependence

Cannabis dependence and tolerance are quite common among regular users of cannabis. Tolerance means that the user requires more cannabis to achieve the same effects they used to get with smaller amounts. Dependence, or addiction, means that cannabis has become central in their life, they may spend much of their time thinking about cannabis and obtaining it, they may have trouble controlling their use, or continue to use cannabis despite experiencing problems.

Dependent users who abruptly stop their cannabis use may have mild withdrawal symptoms, such as sleep disturbance, anxiety and irritability.

Cannabis and Driving

Performance of complex tasks such as driving motor vehicles is impaired after smoking even small amounts of marijuana. Higher doses result in poor performance of simple manual tasks. The degree of impairment depends on the amount of cannabis consumed.

The use of cannabis and alcohol together, or separated by a few hours, besides making some of the unpleasant effects of both drugs much worse (e.g. nausea), can severely impair driving. These effects on driving of the two drugs taken together are considerably greater than the effects of either substance taken alone.

Cannabis Testing

THC and other compounds from cannabis can be detected in the blood and urine for some time after marijuana has been used. These compounds can be stored in body fat, to be gradually excreted from the body. For infrequent users of marijuana, a single occasion of use may be detectable in the urine for several days. Long-term heavy users of marijuana may have cannabis compounds detectable in their urine for many weeks after their last use of cannabis. However, it is difficult to determine how recently a person has used cannabis from blood or urine tests.

The time that it takes before the average person will stop testing positive for THC is extremely variable and dependent on several factors. THC is the only one of the illicit drugs that is stored in the fat tissue, so it can take longer to be cleared from the system. Every individual has a different body size and shape and metabolism, which are all factors in how quickly the drug will be eradicated.

The concentration of THC can also vary greatly between plants, from 1-30% of the total dry weight, thus a person who ingests or smokes marijuana with a very high THC level will probably take longer than someone who has taken marijuana with a low THC level to clear the drug from their system. It is very dependant on how much an individual has smoked, how often, what they have smoked and how long they have been smoking for.

Usually someone who has one dose of marijuana and is not a common smoker it would probably take between 1-4 days to be cleared from the system, but for a very heavy and constant smoker it can take up to 4 weeks. For a very heavy and constant smoker, with some form of metabolic disorder, ie Hepatitis C, it can take up to 8 weeks.

THC Chemical Structure