Post-Marketing Reporting Patterns of Ceftazidime–Avibactam and Ceftolozane–Tazobactam: Analysis of Adverse Event Reports from EudraVigilance

Background/Objectives: Ceftazidime/avibactam (CA) and ceftolozane/tazobactam (CT) are WHO Reserve-group antibiotics increasingly used for multidrug-resistant Gram-negative infections. Comparative post-marketing pharmacovigilance data remain limited. Methods: A retrospective pharmacovigilance study was conducted using Individual Case Safety Reports (ICSRs) retrieved from the EudraVigilance database. Reports listing CA or CT as suspected drugs were included. Comparative reporting analyses were performed using reporting odds ratios (RORs) with 95% confidence intervals (CIs) at System Organ Class (SOC) and Preferred Term (PT) levels. Results: A total of 1414 ICSRs were identified (CA: 967; CT: 447). Serious reports were more frequent for CA than CT (91.0% vs. 78.7%), whereas fatal outcomes were proportionally higher for CT (21.0% vs. 12.8%). At the SOC level, CA showed higher reporting for hepatobiliary disorders (ROR 2.00; 95% CI 1.20–3.35), investigations (ROR 2.67; 95% CI 1.92–3.71), nervous system disorders (ROR 1.51; 95% CI 1.07–2.15), and psychiatric disorders (ROR 3.25; 95% CI 1.37–7.72). At the PT level, CA showed higher reporting for encephalopathy (ROR 4.25; 95% CI 1.28–14.09), blood creatinine increased (ROR 7.37; 95% CI 1.76–30.93), platelet count decreased (ROR 26.9; 95% CI 3.71–195.0), and diarrhoea (ROR 2.83; 95% CI 1.09–7.34). Death was less frequently reported for CA relative to CT (ROR 0.17; 95% CI 0.10–0.29). Conclusions: This EudraVigilance-based analysis identified distinct reporting patterns for CA and CT. CA showed higher reporting for neurological, hepatobiliary, and laboratory-related events, whereas CT reports more frequently involved infection-related contexts. These findings support continued post-marketing surveillance, while clinical monitoring should follow established clinical guidance and product information.