This study aimed to compare the effectiveness and safety of standard-dose and high-dose tigecycline in pneumonia caused by carbapenem-resistant Acinetobacter baumannii (CRAB).

This retrospective, propensity score-matched study, conducted between January 2018 and April 2023, included adult patients with CRAB pneumonia who received tigecycline for at least five days. Patients were categorized into standard-dose (100  mg loading dose, followed by 2x50 mg) and high-dose (200  mg loading dose, followed by 2x100 mg) groups. Propensity score matching was performed to minimize baseline differences between groups. After matching, factors associated with 30-day mortality were evaluated using conditional logistic regression. Clinical and microbiological success and adverse events were compared.

A total of 170 patients were analyzed, including 69 in the standard-dose and 101 in the high-dose group. After matching, 62 patients remained in each group. Clinical success was 48.3 % in the standard-dose and 40.4 % in the high-dose group ( p  = 0.406). Seven-day and 30-day mortality were 8.1 % vs. 11.3 % ( p  = 0.544) and 43.5 % vs. 56.5 % ( p  = 0.151), respectively. Microbiological success was higher with high-dose tigecycline (50.9 % vs. 26.5 %, p  = 0.012). In multivariate analysis, only the SOFA score independently predicted 30-day mortality (aOR 1.73, 95 % CI 1.09–2.76). Adverse events, particularly elevations in liver enzymes, bilirubin, and thrombocytopenia, were more frequent in the high-dose group.

High-dose tigecycline improved microbiological eradication but did not enhance survival or clinical outcomes and was associated with greater toxicity. These findings support cautious use of high-dose tigecycline in CRAB pneumonia pending randomized controlled trials.