Background: The kidneys play a central role in maintaining internal balance, regulating endocrine function, and eliminating metabolic waste. Because of their high metabolic activity and extensive blood flow, they are highly susceptible to nephrotoxic damage, particularly from drug effects. Vancomycin and gentamicin are frequently prescribed for serious bacterial infections; however, their concurrent or high-dose use may influence renal hemodynamics. Renal Doppler ultrasonography, particularly the acceleration time (AT) parameter, provides a reliable non-invasive means to detect subtle hemodynamic alterations before structural injury develops. This study investigated the impact of different vancomycin dosages, alone and in combination with gentamicin, on renal AT in clinically healthy rabbits. Methods: Twenty clinically healthy rabbits were allocated into four groups. Group 1 was administered vancomycin (50mg/kg IV q12h) for 5 days. Group 2 received both vancomycin (50 mg/kg IV q12h) and gentamicin (8 mg/kg IM q24h) for 5 days. Group 3 received both vancomycin (30 mg/kg IV q12h) and gentamicin (8mg/kg IM q24h) for 5 days. Group 4 was given vancomycin (30 mg/kg IV q12h). Ultrasound examinations were conducted before treatment initiation, 2 and 5 hours after administration on each day during the treatment phase, and 24 hours after the final dose. Results: Within-group analysis revealed a pronounced increase in AT values from day 1 to day 5 compared with baseline in Group 1 (p < 0.05). A notable reduction in AT was observed in Group 3 at the fifth-hour evaluation on day 5 (p < 0.05). Groups 2 and 4 displayed no significant within-group variations. In the between-group comparison, the first three groups exhibited higher AT values than Group 4 at several time points (p < 0.05). Conclusion: Administration of high-dose vancomycin led to a marked increase in renal acceleration time compared with baseline, while its combination with gentamicin produced dose-dependent variations in renal hemodynamic responses.

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