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Marijuana consists of the leaves and flowering parts of the plant Cannabis sativa. It usually is smoked in cigarettes (“joints” or “reefers”) or pipes or added to food (usually cookies, brownies, or tea). Resin from the plant may be dried and compressed into blocks called hashish. Marijuana contains a number of cannabinoids; the primary psychoactive one is delta-9-tetrahydrocannabinol (THC). THC is also available by prescription in capsule form (dronabinol [Marinol]). THC is used medically as an appetite stimulant for patients with such conditions as AIDS-related anorexia; it also is used as treatment for vomiting associated with cancer chemotherapy, for chronic pain, and for multiple sclerosis, glaucoma, and other disorders.

Synthetic cannabinoid analogs such as JWH-018 and many similar compounds, sold as “K2” or “Spice” and in some so-called “herbal” preparations, are banned in some states but available via the Internet. These may produce acute toxicity similar to that seen with THC.

  1. Mechanism of toxicity

    1. THC, which binds to anandamide receptors in the brain, may have stimulant, sedative, or hallucinogenic actions, depending on the dose and time after consumption. Both catecholamine release (resulting in tachycardia) and inhibition of sympathetic reflexes (resulting in orthostatic hypotension) may be observed.

    2. Pharmacokinetics. Only about 10–20% of ingested THC is absorbed into the bloodstream, with onset of effects within 30–60 minutes and peak absorption at 2–4 hours. It is metabolized by hydroxylation to active and inactive metabolites. Elimination half-life is 20–30 hours but may be longer in chronic users.

  2. Toxic dose. Typical marijuana cigarettes contain 1–3% THC, but more potent varieties may contain up to 15% THC. Hashish contains 3–6% and hashish oil 30–50% THC. Dronabinol is available in 2.5-, 5-, and 10-mg capsules. Toxicity is dose-related, but there is much individual variability, influenced in part by prior experience and degree of tolerance.

  3. Clinical presentation

    1. Subjective effects after smoking a marijuana cigarette include euphoria, palpitations, heightened sensory awareness, and altered time perception, followed after about 30 minutes by sedation. More severe intoxication may result in anxiety, impaired short-term memory, depersonalization, visual hallucinations, and acute paranoid psychosis. Cannabis use may precipitate or exacerbate psychosis in individuals with schizophrenia or bipolar disorder. Occasionally, even with low doses of THC, subjective effects may precipitate a panic reaction. Acute cannabis intoxication may result in impaired driving and motor vehicle accidents. Cannabis dependence, both behavioral and physical, occurs in 7–10% of users.

    2. Physical findings may include tachycardia, orthostatic hypotension, conjunctival injection, incoordination, slurred speech, and ataxia. Stupor with pallor, conjunctival injection, fine tremor, and ataxia have been observed in children after they have eaten marijuana cookies.

    3. Other health problems. Marijuana use has been associated with precipitation of acute myocardial infarction, usually in people with underlying coronary disease, but sometimes in those without, as well as arrhythmias including marked sinus tachycardia, atrial fibrillation, and ventricular tachycardia and fibrillation. Salmonellosis and pulmonary aspergillosis are reported from use of contaminated marijuana. Marijuana may be contaminated by paraquat, but paraquat is destroyed by pyrolysis, and there ...

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