Cephalexin Hydrochloride

In a double‑blind pilot RCT at two Canadian EDs, 69 adults with non‑purulent cellulitis were randomized to high‑dose (1000 mg) or standard‑dose (500 mg) cephalexin four times daily for 7 days. Recruitment rate was 51.5%, exceeding the target of 35%, and loss to follow‑up was 6.1%, demonstrating feasibility for a full‑scale trial. Treatment failure occurred in 3.2% of the high‑dose arm versus 12.9% of the standard‑dose arm. Minor adverse events were more frequent with high‑dose. No unplanned hospitalizations occurred. The authors conclude that a larger trial is warranted to confirm these preliminary findings.

Fig. 1 CONSORT flow diagram. (Yadav K, et al., 2023)

Using an in vitro tripartite model of C57Bl/6 murine bone‑marrow‑derived macrophages and cephalexin against S. aureus, the joint bactericidal effect depended strongly on inoculum size. At ≤10⁶ CFU/mL, macrophages cooperated with cephalexin to enhance killing. At 10⁷ CFU/mL, macrophages were overwhelmed (increased cell death) and actually protected the bacteria from cephalexin, resulting in higher final bacterial counts than cephalexin alone. These findings suggest that at the early stage of infection or at the end of antibiotic treatment (low bacterial burden), host‑drug cooperation may facilitate bacterial clearance.

Fig. 2 Time-kill curves of extracellular S. aureus exposed to cephalexin and/or macrophages. (Lallemand EA, et al., 2021)