Cannabis use disorder

Background

• Cannabis refers to the plants within the Cannabaceae family (marijuana), which includes Cannabis indica and C. sativa
• Cannabis products are being prescribed for adjunctive management of chronic pain
• Some people who use cannabis can develop a substance use disorder

Pathophysiology

• The primary psychoactive chemical is tetrahydrocannabinol (THC)
  • THC content of cannabis has increased from 3% in the 1970s to 12% mroe recently
• Half-life with occasional use is 1.3 days, but with frequent use increases to 5 to 13 days due to sequestration in fat

Risk Factors

• Younger age
• Male sex
• Lower socioeconomic status
• Early onset of cannabis use
• Other substance use concerns, including nicotine, alcohol, cocaine, and opioids
• Family history of substance use disorders
• Concurrent mental health disorders

Clinical Manifestations

Acute intoxication

• Positive effects include relaxation, euphoria, heightened perception, sociability, sensation of time slowing, increased appetite, and decreased pain
• Negative effects include paranoia, dry mouth, tachycardia (especially with alcohol coingestion), anxiety, drowsiness, impaired short-term memory, poor attention, and decreased coordination and balance
• Essentially impossible to overdose

Cannabis hyperemesis syndrome

• Complicates as much as 30% of chronic, daily cannabis use
• Causes severe cyclic nausea and vomiting, resolution with cannabis cessation, abdominal pain
• Symptoms improve with hot showers or baths
• Minor features include age less than 50 years, weight loss more than 5 kg, morning symptoms, normal bowel habits, and a negative diagnostic evaluation
• The only treatment is abstinence from cannabis
  • Standard antiemetics are typically unhelpful
  • May improve with lorazepam, haloperidol, and topical capsaicin cream

Withdrawal

• Occurs in about a third of people after heavy, prolonged use
• Requires three or more of the following, within 1 week of cessation
  • Irritability, anger, or aggression
  • Nervousness or anxiety
  • Sleep difficulty (insomnia, disturbing dreams)
  • Decreased appetite or weight loss
  • Restlessness
  • Depressed mood
  • At least one of: abdominal pain, shakiness/tremors, sweating, fever, chills, or headache

Diagnosis

• Uses the diagnostic criteria for any substance use disorder
• Heavy use is detectable for up to 30 days in urine
  • Indirect exposure (e.g. second-hand) will generally not generate a positive urine test

Management

Screening

• The CUDIT-R tool is a self-screening questionnaire

Treatment

• Cognitive behavioural therapy (CBT) and motivational enhancement therapy (MET) increases abstinence, decreases frequency of use, decreases severity of dependence, and decreases severity of cannabis-related problems
• There are no proven and approved pharmacologic interventions
• The following have been investigations
  • Gabapentin 1200 mg daily may decrease use
  • Cannabis replacement therapy with dronabinol or nabiximols may decrease withdrawal and increase retention in treatment programs, but not statistically significant
  • The following have been studied and found to not be useful: SSRIs, antidepressants, mixed-action antidepressants, atypical antidepressants, anxiolytics, and norepinephrine reuptake inhibitors
  • Mixed results for N-acetyl cysteine and naltrexone

Pain management

• One observational study suggests that cannabis use is not opioid sparing, does not reduce pain scores, and decreases activity scores 1
  • However, it is still under active research for chronic non-cancer pain
• Avoid prescribing cannabis products to patients with substance use disorders without the involvement of an addiction medicine specialist

Prevention

• Prevention strategies include delaying onset of cannabis use, not driving while intoxicated, and avoiding smoked cannabis