Marijuana consists of the leaves and flowering parts of the plant Cannabis sativa. It is usually smoked in cigarettes (“joints” or “reefers”), or pipes or added to food (eg, cookies, brownies, candy or tea), and sold as capsules and lozenges. Resin from the plant may be dried and compressed into blocks called hashish. The source may be illicit or via cannabis dispensaries available in many US states. Marijuana contains a number of cannabinoids; the primary psychoactive one is delta-9-tetrahydrocannabinol (THC). THC in liquid form can be vaped using electronic cigarettes and is available by prescription in capsule form (dronabinol). Marijuana can also be inhaled using an electronic device which vaporizes THC without combusting marijuana. THC is used medically as an appetite stimulant for patients with such conditions as AIDS-related anorexia; it is also used as treatment for vomiting associated with cancer chemotherapy, chronic pain, management of anxiety, sleep, spasticity associated with multiple sclerosis, glaucoma, and other disorders. In some US states, cannabis products are legal for medical use, and in others for recreational use.

Cannabidiol (CBD) is a constituent of cannabis that does not produce THC-like intoxication. Hemp is a variant of C. sativa that contains high concentrations of cannabidiol and low levels of THC. Cannabidiol and hemp extracts are available over the counter in stores and via the Internet, and are marketed as anxiolytics, anti-emetics, anti-inflammatories, antioxidants, and treatments for local pain, acne, and opiate use disorder. Cannabidiol is available by prescription for treatment of some pediatric seizure 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. They are commonly sprayed onto dried plant material and smoked. Alternatively, liquid preparations may be vaped, and ingestions are also reported. Intoxication is similar to THC, though some have been associated with seizures and acute kidney injury. Nabilone is a synthetic cannabinoid marketed as a medication for nausea and vomiting during cancer chemotherapy.

1. THC, which binds to cannabinoid (anandamide) CB₁ and CB₂ 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. Due to first pass metabolism, 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. Blood THC levels decline rapidly after inhalation due to tissue redistribution, followed by an elimination half-life of 20-30 hours, which may be longer in chronic users.

On average marijuana cigarettes contain 12% THC, but more potent varieties may contain up to 30% THC. Hashish contains 3-6% and hashish oil 30-50% THC. THC extracted from marijuana using butane (butane hash oil) can be nearly 100% THC. Dronabinol is available in 2.5-, 5-, and 10-mg capsules. Edibles can contain from 1 to over 100 mg THC per serving. Toxicity is dose related, but there is much individual variability, influenced in part by prior experience and degree of tolerance.

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 with THC or synthetic cannabinoids may result in anxiety, agitation, 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 5-10% of users. A cannabis withdrawal syndrome is seen after stopping use in heavy chronic users, consisting of irritability, anxiety, fatigue, sleep disturbance often with abnormal dreams, and depression.
2. Physical findings may include tachycardia, hypertension, 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. Seizures have been reported in children but are rare.
3. Other health problems. Due to its sympathomimetic effects, THC use has been associated with precipitation of acute myocardial infarction or sudden death, 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 and stroke. Salmonellosis and pulmonary aspergillosis are reported from use of contaminated marijuana. Chronic heavy marijuana use has been associated with various psychiatric disorders, chronic bronchitis, and an increased risk for coronary artery disease. Cannabinoid hyperemesis syndrome is associated with chronic heavy marijuana use, and is characterized by recurrent nausea, abdominal pain and vomiting which resolves after cessation of cannabis use.
4. E-cigarette or vaping associated acute lung injury (EVALI) is a syndrome of diffuse lung injury associated with vaping THC adulterated with vitamin E acetate. A cluster of several hundred cases, many requiring hospitalization and a number of deaths were reported in 2019 and early 2020. CT chest typically shows ground glass opacities, and pathology shows diffuse alveolar damage with lipid-laden alveolar macrophages.
5. Intravenous use of marijuana extract or hashish oil may cause dyspnea, abdominal pain, fever, shock, disseminated intravascular coagulation, acute renal failure, and death.

Usually is based on the history and typical findings, such as tachycardia and conjunctival injection, combined with evidence of altered mood or mental status.

1. Specific levels. Blood THC levels are available but are not commonly measured. Metabolites of THC may be detected in the urine by enzyme immunoassay up to several days after a single acute exposure or several weeks after chronic THC exposure. Urine levels do not correlate with the degree of intoxication or functional impairment, but blood THC levels of 2.5-5 ng/mL or higher are very suggestive of intoxication. Hemp and hemp seed products (eg, hemp seed nutrition bars) may cause a positive urine THC test due to low levels of THC in the plant.
2. Useful laboratory studies include white blood cell count, electrolytes and glucose, cardiac troponin, EKG, and in case of pulmonary symptoms, arterial blood gas and chest CT.

1. Emergency and supportive measures
   1. Most psychological disturbances can be managed by simple reassurance, possibly with adjunctive use of lorazepam, diazepam, or midazolam.
   2. Sinus tachycardia usually does not require treatment but, if necessary, may be controlled with beta blockers.
   3. Orthostatic hypotension responds to head-down position and IV fluids.
   4. Acute lung injury associated with vaping THC should be managed supportively.
2. Specific drugs and antidotes. There is no currently available specific antidote.
3. Decontamination after ingestion. Administer activated charcoal orally if conditions are appropriate (see Table I-37). Gastric lavage is not necessary if activated charcoal can be given promptly.
4. Enhanced elimination. These procedures are not effective owing to the large volume of distribution of cannabinoids.