What is the best course of action for a patient experiencing recurrent vomiting?

Management of Recurrent Vomiting

For patients with recurrent vomiting, initiate dopamine receptor antagonists (metoclopramide, prochlorperazine, or haloperidol) as first-line therapy, administered around-the-clock rather than PRN, and add a 5-HT3 antagonist like ondansetron if symptoms persist after 4 weeks. 1, 2

Initial Diagnostic Workup

Before initiating treatment, obtain specific laboratory tests to identify reversible causes and assess severity:

• Order complete blood count, serum electrolytes (particularly potassium, magnesium, chloride), glucose, liver function tests, lipase, and urinalysis to exclude metabolic causes and quantify dehydration 1, 2
• Check for hypokalemia, hypochloremia, and metabolic alkalosis, which are the characteristic electrolyte derangements from prolonged vomiting 2
• Consider testing for hypercalcemia, thyroid function, and cortisol if initial workup is unrevealing 1
• Obtain urine drug screen specifically for cannabis, as Cannabis Hyperemesis Syndrome is common in younger patients and requires 6 months of cessation for definitive diagnosis 1
• Perform one-time esophagogastroduodenoscopy (EGD) or upper GI imaging to exclude mechanical obstruction, then avoid repeated imaging unless new symptoms emerge 1, 2

First-Line Pharmacologic Management

Dopamine receptor antagonists are the cornerstone of initial therapy:

• Start metoclopramide 10 mg IV/PO every 6 hours, which is FDA-approved for diabetic gastroparesis and recurrent gastric stasis, and is particularly effective when gastric dysmotility contributes to symptoms 1, 3
• Alternative dopamine antagonists include prochlorperazine or haloperidol 1 mg IV/PO every 4 hours, which have different receptor profiles and may be better tolerated in some patients 1
• Administer these medications on a scheduled, around-the-clock basis rather than PRN, as prevention of vomiting is far more effective than treating established symptoms 4, 1, 2
• Monitor young males closely for extrapyramidal symptoms (dystonia, akathisia), and treat immediately with diphenhydramine 50 mg IV if they develop 1, 2

Second-Line Therapy for Persistent Symptoms

If vomiting continues after 4 weeks of dopamine antagonist therapy:

• Add ondansetron 8-16 mg IV or 4-8 mg PO every 8 hours, as this 5-HT3 antagonist acts on different receptors and provides complementary antiemetic coverage 1, 2
• Monitor QTc interval when using ondansetron, especially in combination with other QT-prolonging medications like metoclopramide or haloperidol 1, 2
• Combine ondansetron with dexamethasone 10-20 mg IV, as this combination is superior to either agent alone based on category 1 evidence 1

Breakthrough and Refractory Vomiting

When standard therapy fails, escalate using multiple concurrent agents:

• Use agents from different drug classes simultaneously rather than sequential monotherapy, as no single agent has proven superior for breakthrough emesis 4, 1
• Add corticosteroids (dexamethasone) and benzodiazepines (lorazepam) to address different neurotransmitter pathways 4, 1, 5
• Consider haloperidol, olanzapine, or scopolamine transdermal patch as miscellaneous agents with distinct mechanisms 4
• Administer medications via alternating routes (IV, rectal, sublingual, nasal spray) when oral route is not feasible due to ongoing vomiting 4, 1
• For truly refractory cases, dronabinol 2.5-7.5 mg PO every 4 hours is FDA-approved for nausea unresponsive to conventional antiemetics 4, 1

Essential Supportive Care

Concurrent with pharmacologic therapy:

• Ensure fluid intake of at least 1.5 L/day and correct electrolyte abnormalities, particularly hypokalemia and hypomagnesemia 1, 2
• Provide thiamin supplementation to prevent Wernicke's encephalopathy in patients with prolonged vomiting 1
• Add H2 blocker or proton pump inhibitor if dyspepsia is present, as patients may confuse heartburn with nausea 4, 1
• Recommend small, frequent, bland meals (BRAT diet: bananas, rice, applesauce, toast) and avoidance of trigger foods 4

Critical Pitfalls to Avoid

• Never use antiemetics in suspected mechanical bowel obstruction, as this masks progressive ileus and gastric distension 1, 2
• Do not stigmatize patients with cannabis use—offer treatment even with ongoing use, as therapies can still be effective 1
• Avoid repeated endoscopy or imaging unless new symptoms develop 1, 2
• Do not use PRN dosing—scheduled administration is essential for prevention 4, 2

Special Consideration: Cyclic Vomiting Syndrome

If the patient has stereotypical episodes of acute-onset vomiting lasting less than 7 days, separated by at least 1 week of baseline health, with at least 3 discrete episodes in the past year:

• Recognize this as Cyclic Vomiting Syndrome (CVS), which requires distinct prophylactic therapy 4
• For moderate-severe CVS (≥4 episodes/year lasting >2 days requiring ED visits), initiate prophylactic therapy with tricyclic antidepressants (amitriptyline 25 mg at bedtime, titrated to 75-150 mg) or anticonvulsants (topiramate 25 mg daily, titrated to 100-150 mg) 4
• For abortive therapy during prodromal phase, use sumatriptan or high-dose ondansetron, as early intervention during the prodrome has the highest probability of aborting an episode 4