Patient with a 2‑day history of pruritic maculopapular rash spreading from thighs to arms/legs and new foot edema after starting bilastine and cetirizine, now with generalized rash, bipedal edema, and stable vital signs—what is the appropriate treatment plan?

Treatment Plan for Suspected Drug-Induced Hypersensitivity Reaction

Immediate Management

Discontinue bilastine and cetirizine immediately, as the temporal relationship (rash worsening after starting these antihistamines with new bipedal edema) strongly suggests drug-induced hypersensitivity rather than simple urticaria. 1

Acute Symptomatic Treatment

• Oral corticosteroids: Prednisone 0.5–1 mg/kg/day (approximately 40–60 mg daily for average adult) for 4–6 days, then taper over 2 weeks 1, 2

  • A 4-day prednisone burst (20 mg every 12 hours) significantly improves both pruritic symptoms and clinical rash resolution compared to antihistamines alone in acute urticaria 2
  • Start proton pump inhibitor for GI prophylaxis during corticosteroid use 1

• Alternative non-sedating antihistamine (different from bilastine/cetirizine): Loratadine 10 mg daily or fexofenadine 180 mg daily for symptomatic pruritus relief 1

  • These provide antipruritic effects without the risk of cross-reactivity with the suspected culprit drugs

• Sedating antihistamine for nighttime pruritus: Hydroxyzine 10–25 mg at bedtime only (not QID) to minimize daytime sedation and performance impairment 1, 3

  • Avoid multiple daily dosing due to significant cognitive impairment and fall risk 3

Topical Management

• High-potency topical corticosteroid for body: Clobetasol propionate 0.05% or betamethasone dipropionate cream/ointment twice daily 1
• Low-potency topical corticosteroid for face: Hydrocortisone 2.5% or desonide cream twice daily 1
• Emollients: Fragrance-free, cream or ointment-based moisturizers applied liberally at least once daily to entire body 1

Monitoring and Reassessment

• Reassess in 48–72 hours: If no improvement or worsening symptoms (increased edema, systemic symptoms, mucosal involvement), escalate to dermatology consultation same-day 1
• Laboratory evaluation if symptoms persist or worsen: CBC with differential, comprehensive metabolic panel to rule out systemic hypersensitivity 1
• Monitor for warning signs: Fever, mucosal involvement, skin pain, blistering, or facial/tongue swelling requiring immediate escalation 1

Critical Pitfalls to Avoid

• Do not rechallenge with bilastine or cetirizine: The temporal relationship and worsening after initiation strongly suggest drug causality 1
• Do not use first-generation antihistamines during daytime: Diphenhydramine causes excessive sedation, performance impairment, and 1.5× increased risk of fatal automobile accidents 3
• Do not delay corticosteroids: Early systemic corticosteroid administration (within 2 days) significantly improves outcomes in drug-induced hypersensitivity reactions 2
• Do not use prolonged corticosteroid courses without tapering: Risk of HPA axis suppression with courses >2 weeks 4

Medication List

1. Prednisone 40–60 mg PO daily (0.5–1 mg/kg) × 4–6 days, then taper over 2 weeks 1, 2
2. Loratadine 10 mg PO daily OR Fexofenadine 180 mg PO daily 1
3. Hydroxyzine 10–25 mg PO at bedtime only (for severe nighttime pruritus) 1, 3
4. Clobetasol propionate 0.05% cream/ointment to body twice daily 1
5. Hydrocortisone 2.5% cream to face twice daily 1
6. Omeprazole 20 mg PO daily (GI prophylaxis during steroid use) 1
7. Fragrance-free emollient cream liberally to entire body at least once daily 1