What is the best course of treatment for a 20-year-old patient presenting with nausea and vomiting?

Management of Nausea and Vomiting in a 20-Year-Old Patient

For a 20-year-old with nausea and vomiting, start with a dopamine receptor antagonist (metoclopramide 10 mg orally three times daily or prochlorperazine) as first-line therapy, while simultaneously identifying and treating the underlying cause. 1

Initial Assessment Priorities

Immediately evaluate for these specific conditions that require urgent intervention:

• Rule out pregnancy in females of childbearing age—this is the most common overlooked cause in this age group 2, 3
• Obtain cannabis use history—Cannabis Hyperemesis Syndrome (CHS) is extremely common in 20-year-olds and presents with cyclic vomiting that paradoxically worsens with continued marijuana use 4
• Check for alarm symptoms requiring immediate evaluation: bilious or bloody vomiting, severe abdominal pain suggesting obstruction, altered mental status, or signs of severe dehydration 1, 4
• Review all medications and supplements—medication adverse effects are a leading cause of nausea in young adults 1, 2

Essential Laboratory Evaluation

Order these tests to guide management and assess severity:

• Complete blood count, comprehensive metabolic panel (electrolytes, glucose, renal function), and liver function tests 4
• Urinalysis and urine pregnancy test (if applicable) 4
• Consider thyroid function and morning cortisol if symptoms are chronic 4
• Urine drug screen is warranted given the age group and high prevalence of CHS 4

Critical pitfall: Prolonged vomiting causes hypokalemia, hypochloremia, and metabolic alkalosis—correct electrolyte abnormalities, particularly potassium and magnesium, as these worsen symptoms 4

First-Line Pharmacologic Treatment

Start dopamine receptor antagonists immediately while awaiting test results:

• Metoclopramide 10 mg orally three times daily before meals (particularly effective for gastroparesis and delayed gastric emptying) 1, 4
• Alternative: Prochlorperazine 10 mg orally every 6-8 hours 5, 1
• Alternative: Haloperidol 0.5-2 mg orally every 4-6 hours (especially useful if patient appears anxious or agitated) 5, 6

Monitor for extrapyramidal side effects, particularly in young males who are at highest risk—treat with diphenhydramine 50 mg if these develop 4

Stepwise Escalation for Persistent Symptoms

If vomiting continues after 24-48 hours on dopamine antagonists:

• Add ondansetron (5-HT3 antagonist) 8 mg orally 2-3 times daily 1, 4, 7
• The combination targets different receptor pathways and provides synergistic antiemetic coverage 4
• Ondansetron is available as sublingual tablets, which improve absorption in actively vomiting patients 1
• Caution: Monitor for QTc prolongation when combining ondansetron with other medications 4

For breakthrough nausea despite the above combination:

• Add lorazepam 0.5-1 mg orally every 4-6 hours if anxiety is contributing to symptoms 6
• Consider dexamethasone 10-20 mg in combination with ondansetron—this combination is superior to either agent alone 4

Route of Administration Considerations

The oral route often fails due to ongoing vomiting—use alternative formulations:

• Ondansetron sublingual tablets 8 mg 1
• Prochlorperazine rectal suppositories 25 mg 1
• Intravenous administration if patient requires hospitalization for severe dehydration 1

Administer antiemetics on a scheduled basis rather than as-needed—prevention is far more effective than treating established vomiting 4

Treatment Based on Specific Etiologies

If Cannabis Hyperemesis Syndrome is Suspected:

• Hot showers provide temporary relief and are pathognomonic for CHS 4
• Definitive treatment requires cannabis cessation for at least 6 months 4
• Do not stigmatize the patient—offer abortive therapy (ondansetron plus benzodiazepines) even with ongoing use, as treatments can still provide relief 4
• Capsaicin cream applied topically may help 4

If Gastritis or GERD is Suspected:

• Add proton pump inhibitor (omeprazole 20-40 mg daily) or H2 receptor antagonist 1, 6
• Continue metoclopramide as it promotes gastric emptying 4

If Acute Gastroenteritis:

• Ondansetron 4-8 mg as a single dose facilitates oral rehydration 8
• Caution: Ondansetron may increase stool volume/diarrhea in gastroenteritis 4
• Focus on fluid and electrolyte replacement with small, frequent intake 2

Supportive Care Measures

Essential non-pharmacologic interventions:

• Ensure fluid intake of at least 1.5 liters daily to prevent dehydration 4
• Small, frequent meals rather than large meals 2
• Thiamin supplementation to prevent Wernicke's encephalopathy in patients with persistent vomiting 4
• Avoid trigger foods (fatty, spicy, or strong-smelling foods) 2

When to Obtain Imaging

• One-time upper endoscopy or upper GI imaging if symptoms persist beyond 7 days to exclude obstructive lesions 4
• Avoid repeated endoscopy unless new symptoms develop 4
• Consider CT abdomen/pelvis if acute surgical abdomen is suspected 2

Critical Pitfalls to Avoid

• Never use antiemetics in suspected mechanical bowel obstruction—this masks progressive ileus and gastric distension 1, 4
• Do not overlook pregnancy testing in females—this is the most common missed diagnosis 2, 3
• Avoid long-term benzodiazepine use due to dependence risk 6
• Do not use metoclopramide long-term without reassessing—it carries a black box warning for tardive dyskinesia 1
• Recognize that symptoms are poor predictors of functional versus pathological illness—maintain broad differential 9

Refractory Symptoms Requiring Specialist Referral

If symptoms persist beyond 4 weeks despite the above interventions:

• Consider olanzapine 2.5-5 mg daily (particularly effective in palliative care settings) 5, 6
• Dronabinol 2.5-7.5 mg every 4 hours (FDA-approved cannabinoid for refractory nausea) 5, 4
• Refer to gastroenterology for evaluation of gastroparesis, cyclic vomiting syndrome, or other gastric neuromuscular disorders 10