What is the best approach for treating and managing a patient presenting with vomiting?

Treatment and Management of Vomiting

Begin with dopamine receptor antagonists (metoclopramide 5-10 mg PO/IV three times daily, prochlorperazine, or haloperidol 0.5-2 mg PO/IV every 4-6 hours) as first-line therapy, titrated to maximum benefit and tolerance. 1, 2

Initial Assessment

Identify the underlying cause to guide treatment:

• Screen for medication-induced causes, gastritis/GERD, bowel obstruction, severe constipation, metabolic abnormalities, and gastroparesis 1
• Obtain complete blood count, serum electrolytes, glucose, liver function tests, lipase, and urinalysis to exclude metabolic causes and assess dehydration 3
• Consider testing for hypercalcemia, hypothyroidism, and Addison's disease if clinically indicated 3
• Obtain cannabis use history—Cannabis Hyperemesis Syndrome (CHS) should be suspected if heavy cannabis use preceded symptom onset 3
• Perform one-time esophagogastroduodenoscopy (EGD) or upper GI imaging to exclude obstructive lesions 3

Critical pitfall: Never use antiemetics in suspected mechanical bowel obstruction, as this can mask progressive ileus and gastric distension 2, 3

Stepwise Pharmacologic Management

First-Line: Dopamine Receptor Antagonists

• Metoclopramide 5-10 mg PO/IV three times daily (particularly effective for gastric stasis) 1, 3
• Prochlorperazine (dose varies by route) 2
• Haloperidol 0.5-2 mg PO/IV every 4-6 hours 1, 3
• Monitor for extrapyramidal side effects, particularly in young males 3
• Treat extrapyramidal symptoms with diphenhydramine 50 mg IV if they develop 3

Second-Line: Add 5-HT3 Receptor Antagonists

If symptoms persist after 4 weeks of first-line therapy:

• Ondansetron 4-8 mg PO/IV 2-3 times daily 1, 2, 4
• Granisetron 1 mg PO twice daily or 34.3 mg transdermal patch weekly 1
• Monitor for QTc prolongation when using ondansetron, especially in combination with other QT-prolonging agents 3, 4
• Note: Ondansetron may increase stool volume/diarrhea 3

Administer antiemetics on a scheduled basis rather than PRN, as prevention is far easier than treating established vomiting 3

Adjunctive Therapies Based on Suspected Cause

• For gastritis/GERD: Add proton pump inhibitors or H2 receptor antagonists 1, 2
• For anxiety-related nausea: Add lorazepam 0.5-1 mg PO/IV every 4-6 hours (use 0.25 mg in elderly patients) 1, 2
• For gastroparesis: Continue metoclopramide as it promotes gastric emptying 3

Refractory Symptoms: Combination Therapy

When first- and second-line therapies fail:

• Combine ondansetron 8-16 mg IV with dexamethasone 10-20 mg IV—this combination is superior to either agent alone 3
• Olanzapine 2.5-5 mg PO daily, especially in palliative care settings 1, 2
• Dronabinol 2.5-7.5 mg PO every 4 hours as needed (FDA-approved for refractory nausea) 3
• Consider continuous IV or subcutaneous infusion of antiemetics 2, 3
• Use agents from different drug classes simultaneously rather than sequential monotherapy, as no single agent has proven superior for breakthrough emesis 3

Special Population Considerations

Elderly Patients

• Reduce doses by 25-50% initially (e.g., lorazepam 0.25 mg orally 2-3 times daily) 1
• Monitor closely for extrapyramidal side effects with antipsychotics 1
• Avoid long-term benzodiazepine use due to risk of dependence 1, 2

Chemotherapy-Induced Nausea and Vomiting

• For high-emetic-risk agents (cisplatin): Use four-drug combination of NK1 receptor antagonist, 5-HT3 receptor antagonist, dexamethasone, and olanzapine 5
• For anthracycline plus cyclophosphamide: Use four-drug combination with dexamethasone on day 1 only, olanzapine continued days 2-4 5
• For carboplatin AUC ≥4 mg/mL per minute: Use three-drug combination of NK1 receptor antagonist, 5-HT3 receptor antagonist, and dexamethasone 5
• Provide prophylaxis based on emetogenic potential rather than assessing response with less-effective treatment first 5

Cyclic Vomiting Syndrome

• Prophylaxis: Tricyclic antidepressants are first-line; topiramate, aprepitant, zonisamide, and levetiracetam are second-line 5
• Abortive therapy: Sumatriptan (nasal spray or subcutaneous) plus ondansetron (sublingual tablet) 5
• Sedation is an effective abortive strategy—consider promethazine, diphenhydramine, or benzodiazepines 5
• Alprazolam available in sublingual or rectal forms may be advantageous 5

Acute Gastroenteritis

• Oral rehydration solution (ORS) is first-line therapy for mild to moderate dehydration, even when vomiting is present 3
• Continue ORT during vomiting by waiting 10 minutes, then giving fluid more slowly in sips at short intervals 6
• Ondansetron 0.2 mg/kg oral (maximum 4 mg) reduces gastroenteritis-related vomiting and facilitates ORT 7, 8
• Isotonic IV fluids (lactated Ringer's or normal saline) for severe dehydration, shock, altered mental status, or ORS failure 3

Supportive Care

• Ensure adequate fluid intake of at least 1.5 L/day 3
• Small, frequent meals 9
• Thiamin supplementation to prevent Wernicke's encephalopathy in persistent vomiting 3
• Correct electrolyte abnormalities, particularly hypokalemia and hypomagnesemia 3
• Consider alternating routes (IV, rectal, sublingual) if oral route not feasible 3

Key Pitfalls to Avoid

• Avoid repeated endoscopy or imaging unless new symptoms develop 3
• Do not stigmatize patients with cannabis use—offer treatment even with ongoing use, as therapies can still be effective 3
• Avoid antimotility drugs (loperamide) in children <18 years with acute diarrhea and in inflammatory diarrhea or diarrhea with fever at any age 3
• Monitor for decreased bowel activity, particularly in patients with risk factors for gastrointestinal obstruction 4
• Avoid ondansetron in patients with congenital long QT syndrome 4