A 32-year-old woman with community-acquired pneumonia is started on intravenous ceftriaxone. After 48 hours of therapy, she develops a diffuse maculopapular rash with mild pruritus but remains hemodynamically stable with no respiratory distress. Temperature is 37.2°C, and clinical signs of pneumonia are resolving. What is the most appropriate next step in management?

Explanation

## Clinical Assessment of Beta-Lactam Rash ### Rash Characteristics in This Case The patient presents with a **non-pruritic to mildly pruritic maculopapular rash** without systemic symptoms (stable vitals, no respiratory involvement, afebrile). This is consistent with a **non-IgE-mediated delayed hypersensitivity reaction** (Type IV), which is common with beta-lactams and is **NOT an absolute contraindication** to continuing therapy if clinical benefit outweighs risk. ### Key Point: **Maculopapular rash alone (without angioedema, bronchospasm, or hypotension) during beta-lactam therapy in a clinically improving patient warrants continuation with close monitoring**, not immediate discontinuation. This is a low-risk scenario. ### Management Algorithm ```mermaid flowchart TD A["Beta-lactam rash develops"]:::outcome --> B{"Anaphylaxis or<br/>severe features?"}:::decision B -->|"Yes: angioedema,<br/>bronchospasm,<br/>hypotension"| C["STOP immediately<br/>Give epinephrine<br/>Switch class"]:::urgent B -->|"No: isolated rash,<br/>stable vitals"|D{"Clinical benefit<br/>ongoing?"}:::decision D -->|"Yes: infection<br/>resolving"| E["Continue beta-lactam<br/>+ antihistamine<br/>Monitor closely"]:::action D -->|"No: infection<br/>not improving"| F["Switch to alternative<br/>class"]:::action E --> G["Complete course<br/>Document reaction type"]:::outcome ``` ### Why Continuation Is Safe Here 1. **Non-IgE-mediated rash**: Maculopapular eruptions typically develop 48–96 hours after initiation and do not indicate immediate hypersensitivity. 2. **Clinical improvement**: Pneumonia signs are resolving; stopping effective therapy may worsen outcome. 3. **Hemodynamic stability**: No systemic involvement or progression. 4. **Antihistamine support**: Provides symptomatic relief and may reduce rash progression. ### High-Yield: **The presence of a rash ≠ allergy. Type and timing matter.** Immediate reactions (urticaria, angioedema, bronchospasm within 1 hour) mandate discontinuation; delayed maculopapular rashes in clinically stable, improving patients often permit continuation with monitoring. ### Clinical Pearl: In resource-limited settings and clinical practice, **cross-reactivity between cephalosporins and penicillins is ~1–3% for non-anaphylactic reactions**; continuation with monitoring is often safer than switching to a carbapenem (which carries its own risks and cost). [cite:Harrison 21e Ch 155] [cite:KD Tripathi 8e Ch 48]