Shorter antibiotic courses may match longer ones for canine pneumonia, but evidence is weak

BACKGROUND: Evidence guiding the optimal antibiotic duration for bacterial pneumonia in dogs and cats is limited, and recommended courses often exceed those used in human medicine. This review evaluated whether shorter systemic antibiotic courses are as effective as longer courses for the treatment of bacterial pneumonia in these species. METHODS: This review was registered with the Open Science Framework (https://osf.io/c5n24). MEDLINE, EMBASE, CAB Abstracts, and Scopus were searched from inception to April 2025, and reference lists were hand-searched. Eligible studies were randomized controlled trials or observational studies comparing different antibiotic durations in dogs or cats with suspected or confirmed bacterial pneumonia. Outcomes included clinical, microbiological, or radiographic resolution. Two reviewers independently screened studies, extracted data, and assessed risk of bias using the Cochrane Risk of Bias tool for randomized trials and ROBINS-I for observational studies. Random-effects meta-analysis was performed. RESULTS: 3 studies involving 74 dogs met the inclusion criteria; no eligible studies of cats were found. Two studies were randomized controlled trials, and 1 study was observational. Comparisons evaluated shorter (10 to 14 days) versus longer (21 to 28 days) antibiotic courses. Pooled analysis showed no significant difference in treatment success between shorter and longer durations (OR, 1.13; 95% CI, 0.28 to 4.56). Certainty of evidence was very low due to risk of bias, indirectness, and imprecision. CLINICAL RELEVANCE: Shorter antibiotic courses may be as effective as longer courses for the treatment of canine bacterial pneumonia, but current evidence is insufficient. No data are available for feline pneumonia, highlighting a critical evidence gap. Well-designed trials are needed to inform veterinary guidelines and antimicrobial stewardship.