What is the appropriate workup and management for a 19-year-old female with nausea and vomiting for 4 weeks?

Workup for a 19-Year-Old Female with 4 Weeks of Nausea and Vomiting

The first priority is to obtain a pregnancy test, followed by comprehensive laboratory evaluation including CBC, comprehensive metabolic panel, liver function tests, lipase, urinalysis, and urine drug screen to exclude pregnancy, metabolic causes, and cannabis hyperemesis syndrome. 1

Initial Laboratory Evaluation

• Obtain urine pregnancy test immediately – pregnancy is the most common cause of persistent nausea and vomiting in reproductive-age females and must be ruled out first 2
• Order complete blood count to assess for infection, anemia, or other hematologic abnormalities 1
• Obtain comprehensive metabolic panel including electrolytes, glucose, calcium, and renal function to identify metabolic causes such as hypercalcemia, uremia, or Addison's disease 1
• Check liver function tests (AST, ALT, bilirubin) and lipase to exclude hepatobiliary or pancreatic disease 1
• Perform urinalysis to assess for urinary tract infection or diabetic ketoacidosis 1
• Order urine drug screen with specific attention to cannabis use – Cannabis Hyperemesis Syndrome (CHS) is increasingly common in this age group and should be strongly suspected with heavy cannabis use 1

Critical History Elements

• Cannabis use history is essential – ask specifically about frequency, duration, and amount of cannabis use, as CHS requires heavy use preceding symptom onset and is a common cause in young adults 1
• Determine timing of symptoms relative to meals, as this helps differentiate gastroparesis (worse after eating) from other causes 3
• Ask about associated symptoms including abdominal pain, headache, dizziness, or weight loss to narrow the differential 3, 4
• Review all medications and supplements, as drug-induced nausea is common 3, 4
• Identify trigger foods or activities that worsen or relieve symptoms 2

Imaging and Endoscopic Evaluation

• Perform one-time esophagogastroduodenoscopy (EGD) or upper GI imaging to exclude obstructive lesions, ulcers, or malignancy 1
• Avoid repeated endoscopy or imaging studies unless new symptoms develop 1
• Consider gastric emptying study if gastroparesis is suspected based on postprandial symptom exacerbation 4

Stepwise Pharmacologic Management

First-Line Therapy

• Initiate dopamine receptor antagonist as first-line treatment: metoclopramide 10 mg every 6-8 hours, prochlorperazine 5-10 mg every 6 hours, or haloperidol 0.5-1 mg every 4-6 hours 1, 5, 6
• Metoclopramide is particularly effective as it both blocks dopamine receptors centrally and promotes gastric emptying peripherally 6, 7
• Administer antiemetics on a scheduled basis rather than as-needed, as prevention is more effective than treating established vomiting 1, 5

Second-Line Therapy (If Symptoms Persist After 4 Weeks)

• Add 5-HT3 antagonist: ondansetron 4-8 mg every 8 hours or 16 mg once daily 1, 8
• Ondansetron acts on different receptors than dopamine antagonists, providing complementary antiemetic coverage 2, 1
• Monitor for QTc prolongation when using ondansetron, especially in combination with other QT-prolonging medications 8

Additional Considerations

• If anxiety contributes to symptoms, consider adding lorazepam 0.5-1 mg every 4 hours as needed 5
• For refractory symptoms, add dexamethasone 4-8 mg daily, which reduces nausea and may stimulate appetite 5

Supportive Care Measures

• Ensure adequate hydration with at least 1.5 L/day of fluids 1
• Recommend small, frequent, bland meals (BRAT diet: bananas, rice, applesauce, toast) with high-protein and low-fat content 2
• Advise avoiding spicy, fatty, acidic, and fried foods 2
• Identify and avoid specific trigger foods with strong odors 2
• Consider ginger 250 mg capsules four times daily as adjunctive therapy 2
• Provide vitamin B6 (pyridoxine) 10-25 mg every 8 hours 2
• Supplement with thiamin to prevent Wernicke's encephalopathy in patients with persistent vomiting 1

If Pregnancy is Confirmed

• Quantify severity using the Motherisk Pregnancy-Unique Quantification of Emesis (PUQE) score 2
• Early treatment may reduce progression to hyperemesis gravidarum 2
• Start with vitamin B6 and doxylamine (10 mg/10 mg or 20 mg/20 mg combination) as FDA-approved first-line therapy 2
• Escalate to ondansetron, metoclopramide, or promethazine for moderate to severe cases 2
• Intravenous glucocorticoids may be required for severe hyperemesis gravidarum 2
• Refer to maternal-fetal medicine if symptoms are severe or refractory 2

Cannabis Hyperemesis Syndrome Management

• Definitive diagnosis requires 6 months of cannabis cessation or at least 3 typical cycle lengths without vomiting 1
• Provide abortive and prophylactic antiemetic therapy even with ongoing cannabis use, as treatments can still be effective 1
• Do not stigmatize patients with cannabis use – maintain a non-judgmental approach while counseling on cessation 1
• Hot showers may provide temporary relief and support the diagnosis of CHS 1

Critical Pitfalls to Avoid

• Never use antiemetics in suspected mechanical bowel obstruction, as this can mask progressive ileus and gastric distension 1, 8
• Do not start with excessively high doses of antiemetics in young patients; begin with standard doses and titrate as needed 5
• Monitor for extrapyramidal symptoms with dopamine antagonists, particularly in young patients and males, and treat with diphenhydramine 50 mg if they develop 2, 1, 5
• Avoid repeated endoscopy or imaging unless new alarm symptoms develop 1
• Do not overlook pregnancy testing in any reproductive-age female with nausea and vomiting 2
• Be aware that ondansetron may increase stool volume/diarrhea if gastrointestinal infection is present 1

Reassessment and Follow-Up

• Reassess symptom control and medication tolerance within 24-48 hours of initiating treatment 5
• If nausea persists beyond one week on first-line therapy, reassess the underlying cause and consider opioid rotation if applicable 2
• Monitor for medication side effects including constipation (from 5-HT3 antagonists), sedation (from antihistamines), and extrapyramidal symptoms (from dopamine antagonists) 2, 5
• If symptoms remain refractory despite maximal medical therapy, consider referral to gastroenterology for further evaluation 1