Ceftazidime-avibactam is a β-lactam/β-lactamase inhibitor combination treatment which has been developed to address infections caused by ESBL-, AmpC- and serine carbapenemase-producing Gram-negative bacteria. In elderly patients, significant interindividual variability often leads to inappropriate dosing (subtherapeutic or excessive), compromising efficacy or increasing toxicity risks. This prospective, multicenter study will enroll patients aged ≥60 years receiving ceftobiprole. Using LC-MS/MS for therapeutic drug monitoring (TDM), we will measure plasma concentrations and integrate individual characteristics (age, body weight, creatinine clearance, etc.). Population pharmacokinetic (PPK) modeling with Bayesian forecasting will be employed to estimate individual PK parameters and identify covariates influencing variability, thereby establishing a PPK model for ceftazidime-avibactam in the elderly.

Based on pathogen-specific MIC values, dosing regimens (dose, frequency) will be dynamically optimized to guide precision therapy. Subsequent TDM data will continuously refine the PPK model, creating a self-optimizing system. This framework lays the groundwork for extending individualized treatment strategies to other antimicrobials in geriatric populations.

Inclusion Criteria:

• Aged ≥60 years Scheduled to receive ceftazidime-avibactam therapy for >5 days No prior ceftazidime-avibactam use within 1 month before enrollment

Exclusion Criteria:

• Patients requiring renal replacement therapy (hemodialysis, peritoneal dialysis, or continuous renal replacement therapy [CRRT]) or with renal impairment history (nephrectomy, renal transplantation, solitary kidney, uremia)

Professional Translation for Clinical Research Protocols: Enroll patients aged ≥60 years receiving ceftazidime-avibactam therapy at Chinese PLA General Hospital