Effectiveness and Nephrotoxicity of Polymyxin B among Intensive Care Unit Patients: A Clinical Evaluation

Polymyxin B is a reserve antibiotic, but there has been an upsurge in its use due to a rise in multidrug-resistant gram-negative bacteria. However, nephrotoxicity and resistance concerns persist, with global resistance rates reaching 29%. Effectiveness of Polymyxin B (clinical and microbiological response) and the frequency of nephrotoxicity is not well documented in resource limited settings. Research is essential to guide optimization of Polymyxin B therapy and inform the adoption of measures for early detection of kidney injury to prevent damage. This study aimed to assess the effectiveness of Polymyxin B by evaluating clinical and microbiological responses and determining nephrotoxicity incidence using KDIGO criteria in ICU patients at Moi Teaching and Referral Hospital (MTRH). A prospective observational cohort study was conducted at MTRH ICUs between December 2021 and November 2022, on patients treated with Polymyxin B. Data on demographics, comorbidities, Polymyxin B dosage regimens, clinical responses, and microbiological results were collected. Descriptive statistics summarized patient characteristics, while associations between dosage regimens and outcomes were evaluated using Fisher's exact test and multivariate regression, with a p<0.05 considered statistically significant. Forty-four patients with a mean age of 48 years were included; 66% were male, and cerebrovascular disease was the most common comorbidity. All patients had multidrug-resistant gram-negative infections qualifying for Polymyxin B therapy. Most (89%) received monotherapy, with 86% achieving a good clinical response, 7% experiencing treatment failure, and 7% dying. Doses of 20,000–25,000 IU/Kg/day were associated with microbiological eradication and good clinical response (p<0.001), while 15,000 IU/Kg/day was associated with treatment failure. Acute kidney injury occurred in 48% of patients, with 68% developing hypomagnesemia. Polymyxin B at doses of between 20,000-25,000IU/Kg/day should be considered as a starting dose due to the association with good clinical response, with alternate-day monitoring of serum creatinine levels for early detection of nephrotoxicity.