Individualization of Vancomycin Dosing Using Therapeutic Drug Monitoring in the Treatment of Mrsa Infections

Objectives: This study aimed to evaluate the optimization of vancomycin dosing through therapeutic drug monitoring (TDM) in patients with methicillin-resistant Staphylococcus aureus (MRSA) infections and to assess the duration of vancomycin treatment required to achieve culture negativity in a tertiary care hospital setting. Methods: We conducted a 6-month prospective observational study at a tertiary care hospital in South India. Hospitalized patients aged >18 years who were receiving intravenous vancomycin for MRSA infections were enrolled, and trough serum vancomycin concentrations were measured before the fourth or fifth dose. The proportion of patients achieving therapeutic trough levels (10–20 mg/L) was determined, and time to first negative culture was recorded and analyzed using Fisher’s exact test, Spearman’s rank correlation, ordinal logistic regression, and Kaplan-Meier survival analysis with log-rank tests. Results: A total of 49 patients were included. Following initial weight-based dosing, 53.1% had subtherapeutic trough levels (<15 μg/mL), 22.4% had therapeutic levels (15–20 μg/mL), and 24.5% had supratherapeutic levels (>20 μg/mL). Twenty-one patients (42.8%) required dose adjustment, comprising 15 who required dose escalation and 6 who required dose reduction, while the remaining 28 patients needed no dose modification. Most patients required only a single dose adjustment (n=17), whereas four patients required multiple adjustments, including two patients who needed two adjustments each, one who needed three, and one who needed four. The majority of patients (65.4%) achieved culture negativity within 10 days. After TDM-guided dose adjustments, ordinal logistic regression showed no statistically significant independent effect of post-trough dose escalation on time to culture negativity (adjusted odds ratio 1.42, 95% confidence interval 0.78–2.58; p=0.25), and Kaplan–Meier analysis revealed no significant difference in time to negativity across dose categories (log-rank p=0.48). Conclusion: TDM plays an important role in achieving therapeutic vancomycin levels and safeguarding patient safety. However, in this pilot cohort, higher post-trough doses were not significantly associated with earlier microbiological clearance. These findings support the routine use of TDM in clinical practice while underscoring the need for larger, adequately powered studies using area under the concentration–time curve to the minimum inhibitory concentration-guided monitoring to establish definitive optimal dosing strategies.