What can be done if Emeset (ondansetron) and Perinorm (metoclopramide) are ineffective in controlling vomiting?

Management of Refractory Vomiting When Ondansetron and Metoclopramide Fail

When ondansetron (Emeset) and metoclopramide (Perinorm) fail to control vomiting, adding aprepitant (NK-1 receptor antagonist) combined with dexamethasone is the most effective next-line strategy to achieve symptom control. 1, 2

Step-by-Step Approach to Refractory Vomiting

First Assessment

• Determine the underlying cause of vomiting:
  • Medication-induced
  • Gastrointestinal causes (obstruction, gastroparesis)
  • CNS involvement
  • Metabolic disturbances
  • Psychogenic factors 1

Pharmacological Management

1. Add Dexamethasone:

   • Add 8mg IV/PO daily to enhance antiemetic efficacy 1
   • Particularly useful when there may be inflammation or edema contributing to symptoms

2. Add Aprepitant (NK-1 receptor antagonist):

   • Provides a different and complementary mechanism of action
   • Significantly improves control of both acute and delayed vomiting 3, 2
   • Has shown complete response rates of 69% vs 56% compared to standard therapy 2

3. Consider Olanzapine:

   • Add 5-10mg PO daily for breakthrough nausea and vomiting 1
   • Particularly effective for chemotherapy-induced nausea and vomiting

4. Administration Schedule:

   • Administer antiemetics on a scheduled basis rather than PRN
   • Combine medications from different antiemetic classes for synergistic effect 1

Alternative Approaches

• Benzodiazepines can be effective for anticipatory nausea and vomiting, though efficacy may decrease over time 3

• Behavioral therapies such as progressive muscle relaxation, systematic desensitization, and hypnosis can be effective but may be difficult to implement in acute settings 3

• Chlorpromazine can be considered as an alternative, though it may have more side effects than newer agents 3

Supportive Measures

• Dietary modifications:

  • Small, frequent meals with low-fat content
  • Separating liquids from solids
  • Taking small bites and chewing thoroughly 1

• Hydration:

  • Ensure adequate fluid intake (≥1.5L/day)
  • Vary temperature and flavors of liquids 1

• Monitor for complications:

  • Dehydration and electrolyte abnormalities
  • Consider thiamin supplementation if vomiting persists >2-3 weeks 1

Red Flags Requiring Urgent Evaluation

• Severe abdominal pain
• Focal neurological findings
• Significant weight loss or malnutrition
• Signs of mechanical obstruction 1

Special Considerations

• For chemotherapy-induced vomiting: The combination of a 5-HT3 receptor antagonist with dexamethasone and aprepitant has shown complete response rates of 42.9% in high-dose chemotherapy settings 3

• For radiotherapy-induced vomiting: Antiemetic regimens should be tailored based on the irradiated area and emetogenic risk 3

• For pediatric patients: Ondansetron has sufficient evidence for use in children, even though it may be considered "off-label/on-evidence" 4

Remember to reassess the antiemetic regimen daily and adjust based on response. The combination of medications from different antiemetic classes provides synergistic effects and improves control of refractory vomiting.