What is the etiology of gastric and retrosternal pain associated with smoking marijuana?

Etiology of Gastric and Retrosternal Pain Associated with Marijuana Smoking

Marijuana smoking can cause gastric and retrosternal pain primarily through cannabinoid hyperemesis syndrome (CHS), gastroesophageal reflux, airway irritation, and cardiovascular effects. 1, 2

Cannabinoid Hyperemesis Syndrome (CHS)

CHS is a well-documented cause of gastric pain in regular cannabis users:

• Characterized by stereotypical episodic vomiting in patients using cannabis >4 times per week for >1 year 2
• Diagnostic features include:
  • Cyclic nausea and vomiting
  • Relief from hot showers/baths
  • Resolution after cannabis cessation 2

Gastric Effects of Cannabis

Cannabis affects gastric function through several mechanisms:

• Paradoxical effects on gastric acid secretion:

  • While cannabinoids can initially inhibit gastric acid secretion through CB1 receptor stimulation 3
  • Chronic use can lead to:
    • Increased gastric acid output
    • Stimulation of pepsinogen secretion
    • Decreased mucus production 4

• Altered gastric motility:

  • Cannabis activates CB1 receptors in the myenteric plexus
  • This reduces cholinergic transmission and decreases gastrointestinal transit 5
  • The resulting delayed gastric emptying can contribute to pain and discomfort

Retrosternal Pain Mechanisms

Retrosternal pain from marijuana smoking can be attributed to:

• Respiratory effects:

  • Increased airway reactivity and bronchial irritation 1
  • Smoking-related thermal injury to the respiratory mucosa
  • Coughing episodes that strain chest muscles

• Cardiovascular effects:

  • Beta-adrenergic-mediated tachycardia
  • Potential myocardial ischemia in at-risk individuals 1
  • Orthostatic hypotension with heavy use 1

• Gastroesophageal reflux:

  • Cannabis use is associated with gastroesophageal reflux disease 6
  • Reflux can cause retrosternal burning and pain

Inflammatory Mechanisms

• Cannabis smoke contains irritants similar to tobacco smoke
• These irritants can trigger inflammatory responses in the gastric and esophageal mucosa
• Cannabis can increase bile salt reflux rate and gastric bile salt concentration 4
• Cannabis increases production of platelet activating factor (PAF) and endothelin, which are potent gastric ulcerogens 4

Common Pitfalls in Diagnosis

• Mistaking CHS for cyclic vomiting syndrome or other causes of recurrent vomiting
• Overlooking cannabis use as a potential cause of gastric and chest pain
• Failing to recognize that despite cannabis's anti-inflammatory properties in some contexts, smoked cannabis can be pro-inflammatory in the GI tract
• Not considering that patients may be using cannabis to self-treat underlying GI conditions, which can confuse the clinical picture

Management Considerations

For patients presenting with gastric and retrosternal pain associated with cannabis use:

• Complete cannabis cessation is the definitive treatment, with symptoms typically resolving within 3-6 months 2
• For CHS specifically:
  • IV fluid rehydration
  • Dopamine receptor antagonists (e.g., haloperidol 0.5-2 mg IV or PO every 4-6 hours)
  • Hot showers/baths and topical capsaicin cream can provide symptomatic relief 2

Understanding these mechanisms is crucial for accurate diagnosis and effective management of gastric and retrosternal pain in marijuana users.