What medication can be recommended for nausea in a patient allergic to amoxicillin, amoxicillin-potassium clavulanate, codeine sulfate, colchicine, doxycycline hyclate, morphine, Sulfonamides, tetracycline, beef, and crab?

Antiemetic Recommendation for Patient with Multiple Drug Allergies

For nausea in this patient with extensive drug allergies including morphine and codeine, ondansetron (a 5-HT3 antagonist) is the recommended first-line antiemetic, as it has no cross-reactivity with any of the listed allergies and is highly effective for nausea management. 1, 2

Primary Recommendation: Ondansetron

Ondansetron is safe and appropriate for this patient because:

• No structural relationship to penicillins, opioids, tetracyclines, or sulfonamides 3
• Proven efficacy with 61% complete response rates in preventing nausea and vomiting 2
• Well-tolerated with minimal adverse effects compared to other antiemetics 1

Dosing for Ondansetron

• Standard dose: 4-8 mg IV or PO 1
• Can be repeated every 8 hours as needed 1
• For severe nausea: 8 mg is preferred initial dose 1

Alternative Antiemetic Options

If ondansetron is insufficient or unavailable, the following alternatives are safe given this patient's allergy profile:

Second-Line: Dopamine Receptor Antagonists

• Metoclopramide (10 mg IV/PO) - strongest evidence for non-chemotherapy nausea 1
• Prochlorperazine (5-10 mg IV/PO) 1
• Haloperidol (0.5-2 mg IV/PO) 1

Important caveat: Monitor for dystonic reactions with metoclopramide and prochlorperazine 1

Third-Line: Additional Options

• Olanzapine (2.5-5 mg PO) - effective antipsychotic with antiemetic properties 1
• Lorazepam (0.5-2 mg PO/IV) - particularly useful for anxiety-related nausea 1
• Dexamethasone (4-8 mg IV/PO) - can be added for persistent nausea 1

Critical Allergy Considerations

Medications to AVOID in This Patient

Absolutely contraindicated:

• Diphenhydramine - while commonly used for nausea, this patient has beef allergy and crab allergy, suggesting potential for multiple hypersensitivities; use caution with antihistamines 1
• Promethazine - phenothiazine with antihistamine properties, avoid given multiple drug allergies 4

Opioid Allergy Context

• This patient's morphine and codeine allergies are relevant because opioid-induced nausea affects 40% of patients 5
• If the nausea is opioid-related from past exposure, ondansetron is particularly appropriate 5
• True allergic reactions to opioids are rare; most are pseudoallergic histamine release 4

Sulfonamide Allergy Clarification

• "Sulfa allergy" does NOT contraindicate sulfur-containing drugs, sulfites, or sulfates 4
• Cross-reactivity between sulfonamide antibiotics and non-antibiotic sulfonamides is not clinically significant 6, 7
• However, given this patient's extensive allergy history, avoiding sulfonamide-containing antiemetics is prudent 6

Management Algorithm

Step 1: Start with ondansetron 8 mg IV or PO 1, 2

Step 2: If inadequate response after 30-60 minutes, add metoclopramide 10 mg IV 1

Step 3: For persistent nausea, add dexamethasone 8 mg IV 1

Step 4: Consider lorazepam 0.5-1 mg if anxiety component present 1

Step 5: For refractory cases, substitute or add olanzapine 2.5-5 mg PO 1

Common Pitfalls to Avoid

• Do not use combination H1/H2 antihistamines as first-line given this patient's multiple allergies 1
• Avoid diphenhydramine for dystonic reactions if they occur; use benztropine instead 1
• Do not assume sulfa allergy contraindicates all sulfur-containing medications 4, 6
• Monitor for dystonic reactions with dopamine antagonists, especially in younger patients 1