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Marijuana Toxicity: An Increasing Clinical Challenge

Marijuana Toxicity: An Increasing Clinical Challenge

As marijuana gains acceptance and becomes legal in some states for medical and/or recreational use, it is important to understand its effects on people and the toxicity associated with this drug.

Marijuana’s History

The history of recreational and medicinal use of marijuana dates back several thousand years. The hemp plant, cannabis sativa, became popular in the 1930’s and can be used to make rope, twine and fabric. It is also frequently used by people as a recreational drug. Hash oil is the most potent form of hemp’s extracts. The dried resins are referred to as hashish.

Of the 400 active compounds identified from the cannabis sativa plant, 60 active compounds have been grouped into a category called cannabinoids. The most psychoactive of these is delta-9-tetrahydrocannanbinol (THC) which produces feelings of relaxation, euphoria, increased sensory experience, changes in perception, analgesia and diminishing memory and concentration.

Marijuana’s Potency

Marijuana’s average THC potency has increased due to advances in plant breeding and management. Four decades ago, the average “joint” contained roughly 10 mg of THC. Today, the same marijuana cigarette contains closer to 60-150 mg. Because effects are generally dose-dependent, current marijuana users may encounter greater morbidity than those who used marijuana in the past.

Behavioral Effects of Using Marijuana

THC causes users to get “high.” It causes users to experience feelings of intoxication, detachment, relaxation, altered perception of time and distance, intensified sensory experience, laughter, talkativeness, diminished anxiety, dulled alertness, and mood depression. These effects are dose-dependent, but are also affected by the users’ expectations, mode of administration, peer activity and personality.

Dysphoric reactions to THC are commonly seen and may include panic, somatic sensations, mania, delirium, paranoia and, most frequently, significant anxiety. These reactions usually resolve without intervention.

Mental Effects of Using Marijuana

The most commonly observed effect of using marijuana is the impairment of one’s short-term memory. A subtle worsening of cognitive function has been identified in those who engage in chronic use of marijuana, the severity of which is dependent on the dosage and the duration of use. It is currently believed that in most cases, the cognitive deficits reverse themselves within one week after using the drug.

Cardiovascular Effects of Marijuana Use 

Some users experience a 20 to 100% increase in heart rate which can last from 60 to 180 minutes. THC can cause peripheral vasodilation and postural hypotension leading to syncope and dizziness. Overall cardiac output (which can increase up to 30%) may trigger ischemic events such as angina or infarction. There are scatted reports of congestive heart failure (CHF) and strokes being associated with THC intoxication.

Respiratory Effects of Marijuana Use

Transient bronchodilation has been observed in users of marijuana, as is typical with any inhaled substance. Increased sputum production, cough and bronchospasm are observed more frequently in patients with concurrent tobacco use. Several reports have suggested a link between cannabis smoking and cancer of the respiratory and digestive systems. Furthermore, a lot of illegally distributed marijuana contains Aspergillus, which can cause invasive pulmonary aspergillosis, particularly in immunocompromised patients.

How Marijuana Use Affects Reproductive Ability

High-dose THC causes a reduction in testosterone levels as well as a decrease in sperm motility, viability and production. Additionally, there are scattered clinical reports demonstrating the negative effects of THC on newborns and young children. Three studies have shown a possible risk of non-lymphoblastic leukemia, rhabdomyosarcoma as well as astrocytoma in children exposed to cannabis while in utero.

Marijuana Use Affects Metabolism and Elimination 

THC is metabolized by the hepatic cytochrome P450 system. Elimination half-life of THC can range from 2 to 57 hours after IV or inhalation exposure. Approximately 90% of THC is eliminated from the body in a little less than one week following exposure.

Marijuana’s Toxicity

Although the acute toxicity of marijuana is relatively benign in the average adult, such is not the case for children. A 250 to 1000 mg ingestion of hashish can result in unresponsiveness in one half hour. Pediatric apnea, cyanosis and bradycardia have been reported in children who have had exposure to the drug.


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