How to manage a patient with persistent nausea, vomiting, potential glucose issues, and recent gastrointestinal illness exposure, unrelieved by Pepto-Bismol (bismuth subsalicylate)?

Management of Persistent Nausea and Vomiting with Potential Glucose Issues

Initiate metoclopramide 10-20 mg orally every 6 hours as first-line therapy, obtain comprehensive laboratory testing including complete blood count, comprehensive metabolic panel, lipase, and thyroid function tests, and rule out cannabis hyperemesis syndrome given the patient's age and symptom pattern. 1, 2

Immediate Diagnostic Workup

Laboratory evaluation must include:

• Complete blood count, serum electrolytes, glucose, liver function tests, lipase, and urinalysis to exclude metabolic causes and assess for dehydration 1
• Thyroid-stimulating hormone, calcium, and morning cortisol to evaluate for hypothyroidism, hypercalcemia, and Addison's disease 1
• Urine drug screen specifically for cannabis metabolites, as Cannabis Hyperemesis Syndrome is common in this age group and presents with persistent nausea and vomiting 1
• Hemoglobin A1c to assess glycemic control given her diabetes history 1

Critical consideration: The metallic taste warrants dental evaluation as planned, but also raises concern for medication side effects or metabolic abnormalities that should be identified through laboratory testing 3, 1.

Cannabis Hyperemesis Syndrome Assessment

Obtain detailed cannabis use history, as CHS requires:

• Heavy cannabis use preceding symptom onset 1
• Definitive diagnosis requires 6 months of cannabis cessation or at least 3 typical cycle lengths without vomiting 1
• Do not stigmatize the patient; offer abortive and prophylactic therapy even with ongoing use, as treatments can still be effective 1

Imaging and Endoscopic Evaluation

Perform one-time esophagogastroduodenoscopy (EGD) or upper GI imaging to exclude:

• Gastric outlet obstruction 3
• Peptic ulcer disease 3
• Structural lesions 3, 1

Avoid repeated endoscopy or imaging studies unless new symptoms develop 1, 4.

Stepwise Pharmacologic Management Algorithm

First-Line Therapy (Weeks 1-4)

Metoclopramide is the preferred initial agent:

• Dose: 10-20 mg orally 30 minutes before meals and at bedtime 1, 4, 2
• FDA-approved for diabetic gastroparesis and promotes gastric emptying 2
• Strongest evidence among dopamine receptor antagonists for non-chemotherapy-related nausea 3
• Titrate to maximum benefit and tolerance 1, 4

Alternative dopamine receptor antagonists if metoclopramide is not tolerated:

• Prochlorperazine 10 mg orally every 6-8 hours 1, 4
• Haloperidol 0.5-2 mg orally every 4-6 hours 1, 4

Monitor for extrapyramidal symptoms, particularly in young patients 1, 4.

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

Add ondansetron 4-8 mg orally 2-3 times daily:

• Add rather than replace the dopamine antagonist to target different receptor pathways for synergistic effect 1, 4
• Monitor for QTc prolongation, especially when combined with other QT-prolonging agents 3, 1
• May increase stool volume/diarrhea 1

Third-Line Therapy (If Symptoms Persist Beyond 8 Weeks)

Add dexamethasone 4-8 mg orally three to four times daily:

• Combination of ondansetron with dexamethasone is superior to either agent alone 1, 4
• Particularly effective when combined with metoclopramide and ondansetron 3

Consider continuous IV/subcutaneous infusions if oral route is not feasible 1, 4.

Treatment of Specific Underlying Causes

Gastroparesis Management

If gastroparesis is suspected based on symptoms of early satiety and postprandial fullness:

• Continue metoclopramide as it promotes gastric emptying 3, 1, 2
• Add proton pump inhibitor for gastritis or gastroesophageal reflux 3
• Small, frequent meals and dietary modifications 1

Metabolic Abnormalities

Correct identified abnormalities:

• Hypercalcemia treatment if present 3
• Electrolyte replacement, particularly potassium and magnesium 1
• Optimize glycemic control with continuous glucose monitor as planned 1

Post-Infectious Gastroparesis

Given recent gastrointestinal illness exposure:

• Idiopathic gastroparesis may occur after viral infection 3
• Symptoms may be self-limiting over 4-9 days 3
• Continue symptomatic management while monitoring for resolution 3

Administration Strategy

Administer antiemetics on a scheduled basis rather than as needed:

• Prevention is far easier than treating established vomiting 1, 4
• Around-the-clock dosing provides greatest benefit 3, 1
• Consider alternating routes (rectal, sublingual) if oral route is not feasible due to ongoing vomiting 1, 4

Supportive Care Measures

Ensure adequate hydration and nutrition:

• Fluid intake of at least 1.5 L/day 1
• Small, frequent meals 1
• Thiamin supplementation to prevent Wernicke's encephalopathy in patients with persistent vomiting 1

Critical Pitfalls to Avoid

Never use antiemetics in suspected mechanical bowel obstruction:

• This can mask progressive ileus and gastric distension 1, 4
• Rule out obstruction before initiating therapy 3

Do not delay treatment while awaiting dental evaluation:

• Metallic taste may be related to medication side effects or metabolic abnormalities 3, 1
• Dental infection is unlikely to cause three weeks of persistent nausea and vomiting 1

Avoid repeated endoscopy or imaging unless new symptoms develop 1, 4.

Monitor for extrapyramidal symptoms with dopamine antagonists, particularly in young patients 1, 4.

Reassessment and Escalation

If symptoms persist after 4-8 weeks of optimized therapy:

• Reassess for underlying causes including constipation, medication side effects, and CNS involvement 1, 4
• Consider adding alternative therapies such as acupuncture 4
• Consult or refer to specialized gastroenterology or palliative care services 1, 4

Continuous glucose monitoring implementation:

• Proceed as planned to optimize glycemic control 1
• Hyperglycemia itself can cause antral hypomotility and delayed gastric emptying 3