THE MEASUREMENT OF TOBRAMYCIN CONCENTRATIONS IN PATIENTS WITH HEMATOLOGICAL ONCOLOGY AND TRIAL OF DOSAGE REGIMEN BASED ON PHARMACOKINETICS

• Published in: Japanese Journal of National Medical Services Vol. 50; no. 6; pp. 436 - 440
• Main Authors: TOMIZAWA, Taturu, TAGUCHI, Takahisa, NAKATA, Masanobu, KATSUMATA, Noriyuki, SHINO, Michihiro, TAKENAKA, Takeaki
• Format: Journal Article
• Language: Japanese
• Published: Japanese Society of National Medical Services 1996; 一般社団法人 国立医療学会
• Subjects: dosage regimen; pharmacokinetics; therapeutic drug monitoring; tobramycin; トブラマイシン; 投与設計; 薬物動態学; 薬物治療モニタリング
• ISSN: 0021-1699; 1884-8729
• DOI: 10.11261/iryo1946.50.436

When administering tobramycin (TOB) to hematologic malignant patients treated with the empiric dose, serum TOB concentrations were determined, so we attempted the dosage regimen on the basis of pharmacokinetics. The patients were ages 36-79 years old, 40-66kg in body weight for 13 hematologic malignant patients (male 9, female 4) hospitalized in the National Cancer Center Hospital. Serum TOB concentrations were measured by fluorescence polarization immunoassay using TDx. The pharmacokinetic parameters of each patient and optimum dose were calculated according to the Sawchuk-Zaske dosing method on the basis of the 1-compartment model. Serum samples were obtained just before and after from the 3rd to the 15th intravenous infusions in one hour (1st observation point), then we calculated the pharmacokinetic parameters of each patient. Eachpatient's dose and the dosage interval were individually calculated to obtain desired serum concentrations. We similarly obtained blood samples after the dosage adjustment (2nd observation point) and compared the measured values with the predicted values. Measured peak concentrations at the 1st observation point were 4.47±1.15 μg/ml (mean±SD). 71.4% of the samples did not reach therapeutic ranges. The peak concentrations of 4 entire treatments after the dosage regimen were 8.34±0.74μg/ml, and all measurements reached therapeutic ranges. On the other hand, measured trough concentrations at the 1st observation point were 0.40±0.28μg/ml, where 78.6% did not reach therapeutic ranges. Measured trough concentrations after the dosage regimen were 1.25±0.74μg/ml, and all measurements but one remained in the therapeutic ranges. The doses before the dosage regimen were 2.87±1.12mg/kg/day, and were increased to z.29±0.47mg/kg/day after that. Thus, most of the serum TOB concentrations were below therapeutic ranges in the case of empiric dosing. Therefore, this suggested the necessity of the dosage regimen.