The study aims to present a case study of a patient with supratherapeutic serum gentamicin concentration. An 83-year-old male was admitted to the Department of Internal Medicine for persistent loss of appetite, decompensated heart failure, and pneumonia. He was treated with 240 mg gentamicin daily alongside ampicillin/sulbactam penicillin antibiotic. The trough gentamicin concentrations and estimated glomerular filtration rate from creatinine (eGFRcrea) and cystatin C (eGFRcys) were performed. The patient had the supratherapeutic trough gentamicin concentration of 2.5 mg/L. eGFRcrea was 62 mL/min/1.73m2 and eGFRcys was 25 mL/min/1.73m2. The difference between eGFRcrea and eGFRcys was 148%. Falsely high eGFRcrea in elderly patient led to the supratherapeutic gentamicin concentration even after the standard 240 mg gentamicin dose.

• Keywords
• creatinine, cystatin C, drug overdose, gentamicins, glomerular filtration rate,
• MeSH
• Anti-Bacterial Agents * administration & dosage   blood   MeSH
• Cystatin C * blood   MeSH
• Gentamicins * administration & dosage   blood   therapeutic use   MeSH
• Glomerular Filtration Rate MeSH
• Creatinine blood   MeSH
• Humans MeSH
• Pneumonia drug therapy   MeSH
• Aged, 80 and over MeSH
• Check Tag
• Humans MeSH
• Male MeSH
• Aged, 80 and over MeSH
• Publication type
• Journal Article MeSH
• Case Reports MeSH
• Names of Substances
• Anti-Bacterial Agents * MeSH
• Cystatin C * MeSH
• Gentamicins * MeSH
• Creatinine MeSH