A 28-year-old woman with acute exacerbation of chronic obstructive pulmonary disease presents with purulent sputum, fever, and dyspnea. Sputum Gram stain shows pleomorphic Gram-negative coccobacilli. Culture on chocolate agar yields *Haemophilus influenzae* susceptible to ampicillin. However, the patient reports a severe penicillin allergy (anaphylaxis). What is the most appropriate next step in management?