What is the best course of action for a 15-year-old male with morning nausea and vomiting that improves in the afternoon, lasting for 2 weeks?

Morning Nausea and Vomiting in a 15-Year-Old Male: Diagnostic and Management Approach

This 15-year-old requires immediate evaluation for Cannabis Hyperemesis Syndrome (CHS), cyclic vomiting syndrome (CVS), and metabolic causes, with initial laboratory testing and targeted history taking priority over empiric antiemetic therapy. 1, 2

Immediate Diagnostic Priorities

Critical History Elements

• Cannabis use history is absolutely essential in this age group, as CHS is increasingly common and presents with stereotypical morning vomiting that improves later in the day 1, 2
• Ask specifically about the stereotypical pattern of symptoms: Does he experience prodromal symptoms (sense of doom, anxiety, mental fog, diaphoresis) approximately 1 hour before vomiting onset? 1
• Determine if episodes are truly recurrent and separated by symptom-free intervals (suggesting CVS) or continuous daily symptoms 1
• Document any triggers: stress, sleep deprivation, infections, or specific foods 1
• Assess for associated symptoms during episodes: abdominal pain (present in most CVS patients), headache, bowel urgency, acute diarrhea, shakiness 1

Mandatory Initial Laboratory Testing

Obtain the following tests immediately to exclude metabolic emergencies and assess severity: 2, 3, 4

• Complete blood count, comprehensive metabolic panel (including glucose, electrolytes, liver function tests) 2
• Lipase level 2
• Urinalysis 2
• Urine drug screen (critical in this age group for cannabis detection) 2
• Thyroid-stimulating hormone 4
• Consider calcium level to exclude hypercalcemia 2, 3

Prolonged vomiting causes hypokalemia, hypochloremia, and metabolic alkalosis—these must be identified and corrected. 2

Differential Diagnosis Framework

Cannabis Hyperemesis Syndrome (Most Likely in This Age Group)

• CHS should be the leading diagnosis given the age, morning predominance, and pattern of improvement 1, 2
• Definitive diagnosis requires 6 months of cannabis cessation or at least 3 typical cycle lengths without vomiting 2
• Do not stigmatize the patient—offer treatment even with ongoing use, as therapies can still be effective 2

Cyclic Vomiting Syndrome

CVS is diagnosed clinically using Rome IV criteria: 1

• Stereotypical episodes of acute-onset vomiting lasting <7 days
• At least 3 discrete episodes in a year (with 2 in prior 6 months)
• Episodes separated by at least 1 week of baseline health
• Absence of vomiting between episodes

However, this patient's 2-week continuous daily pattern does NOT fit classic CVS, which requires discrete episodes separated by wellness periods. 1

Other Critical Considerations

• Gastroparesis or gastric outlet obstruction: Consider if abdominal pain or early satiety present 1, 3
• Intracranial pathology: Unlikely without headache or neurologic signs, but morning vomiting can indicate increased intracranial pressure 3, 4
• Metabolic causes: Hypercalcemia, hypothyroidism, Addison's disease, diabetes 2, 3

Imaging and Endoscopy Decisions

One-time upper GI imaging or esophagogastroduodenoscopy (EGD) is recommended to exclude obstructive lesions, but avoid repeated studies. 2

Indications for urgent imaging: 3, 4

• Severe abdominal pain suggesting obstruction
• Alarm symptoms: weight loss, dysphagia, hematemesis
• Abnormal abdominal examination findings

If intracranial pathology is suspected (severe headache, neurologic signs), obtain head CT immediately. 4

Pharmacologic Management Algorithm

Step 1: First-Line Dopamine Antagonist

Initiate metoclopramide 10-20 mg orally three to four times daily as first-line therapy. 5, 2

• Metoclopramide has dual action as dopamine antagonist and prokinetic agent 5
• Administer on a scheduled basis, not as-needed—prevention is far easier than treating established vomiting 2
• Alternative: Prochlorperazine 5-10 mg four times daily if metoclopramide contraindicated 5

Critical monitoring: Watch for extrapyramidal symptoms (dystonic reactions), particularly in young males like this patient. 5, 2

• Treat immediately with diphenhydramine 50 mg if extrapyramidal symptoms develop 5, 2

Step 2: Add 5-HT3 Antagonist if Symptoms Persist After 4 Weeks

Add ondansetron 4-8 mg two to three times daily for complementary antiemetic coverage. 5, 2

• Ondansetron acts on different receptors than dopamine antagonists 2
• Monitor for QTc prolongation, especially if combining with other QT-prolonging agents 2

Step 3: Consider Adjunctive Therapy

Add an H2 blocker or proton pump inhibitor if any component of dyspepsia or reflux is present, as patients may confuse heartburn with nausea. 5, 2

Critical Management Pitfalls to Avoid

Never use antiemetics if mechanical bowel obstruction is suspected—this can mask progressive ileus and gastric distension. 2

Avoid repeated endoscopy or imaging unless new symptoms develop. 2

Do not dismiss cannabis use history or fail to screen for it—CHS is common and treatable. 2

Supportive Care Measures

Ensure adequate fluid intake of at least 1.5 liters per day to prevent dehydration. 5, 2

Recommend small, frequent meals at room temperature rather than large hot meals. 5

Consider thiamin supplementation to prevent Wernicke's encephalopathy if vomiting is prolonged. 2

When to Escalate Care

Hospitalization is warranted if: 3, 4

• Severe dehydration or inability to maintain oral intake
• Significant electrolyte abnormalities requiring IV correction
• Suspected acute abdomen or obstruction
• Intractable vomiting despite outpatient management