What antiemetics are used in Multiple System Atrophy (MSA)?

Antiemetics in Multiple System Atrophy (MSA)

For patients with Multiple System Atrophy experiencing nausea and vomiting, 5-HT3 receptor antagonists (such as ondansetron 8 mg once or twice daily) should be used as first-line antiemetic therapy, with metoclopramide as a second-line option at 5-20 mg doses, while carefully monitoring for extrapyramidal side effects.

First-Line Antiemetic Options

• 5-HT3 Receptor Antagonists: These are preferred first-line agents due to their efficacy and lower risk of extrapyramidal side effects 1

  • Ondansetron: 8 mg oral/IV once or twice daily 2
  • Granisetron: 1-2 mg oral daily or 1 mg oral twice daily 1
  • Palonosetron: Single dose on day 1 only (longer-acting) 1

• Corticosteroids: Can be used in combination with 5-HT3 antagonists for enhanced effect 1

  • Dexamethasone: 4-12 mg oral/IV daily 1

Second-Line Antiemetic Options

• Dopamine Receptor Antagonists: Use with caution due to risk of worsening parkinsonian symptoms in MSA 1

  • Metoclopramide: 5-20 mg oral/IV every 4-6 hours 3
  • Monitor closely for extrapyramidal symptoms and dystonic reactions 1
  • Consider diphenhydramine for prevention/treatment of dystonic reactions 1

• Antihistamines: Useful for managing both nausea and anxiety symptoms 1

  • H1 blockers: Diphenhydramine 25-50 mg every 4-6 hours 1
  • H2 blockers: Can be added to regimens for gastrointestinal symptoms 1

Breakthrough Nausea and Vomiting

• For breakthrough symptoms, add one agent from a different drug class 1:
  • Olanzapine: 5-10 mg daily (category 1 recommendation) 1
  • Lorazepam: 0.5-2 mg oral/sublingual/IV every 6 hours 1
  • Haloperidol: 0.5-2 mg oral/IV every 4-6 hours (use with caution in MSA) 1
  • Scopolamine: 1.5 mg transdermal patch every 72 hours 1

Special Considerations in MSA

• Avoid medications that may worsen orthostatic hypotension, which is common in MSA 4
• Position patients upright during and after meals to reduce risk of aspiration, as dysphagia is common in MSA 5
• Monitor for dysphagia which can worsen as MSA progresses and increase aspiration risk 5
• Consider alternative administration routes (IV, transdermal, sublingual) if oral intake is compromised 1

Monitoring and Follow-up

• Assess QT interval when using ondansetron, particularly in patients with cardiac risk factors 2
• Monitor for extrapyramidal symptoms when using dopamine antagonists, which may be difficult to distinguish from underlying MSA symptoms 1
• Evaluate for drug interactions with other medications commonly used in MSA 6

Treatment Algorithm

1. Start with ondansetron 8 mg once or twice daily 2
2. If inadequate response, add dexamethasone 4-8 mg daily 1
3. For persistent symptoms, add lorazepam 0.5-1 mg every 6 hours 1
4. Consider metoclopramide only if symptoms persist despite above measures, starting at lowest effective dose (5 mg) 3
5. For refractory cases, consider olanzapine 5 mg daily 1