Actual use of anti-MRSA drugs in Japan with the focus on arbekacin

The purpose of organizing the anti-MRSA drug TDM study group was to survey how anti-MRS drugs are actually used in clinical settings and to collect information on the serum or plasma concentration, clinical efficacy and safety of anti-MRSA drugs aimed at the establishment of more suitable dosimetry regimens. Clinical cases in which an anti-MRSA drug [arbekacin (ABK), vancomycin (VCM) or teicoplanin (TEIC)] was used and who had undergone TDM during the period from April 1999 to December 2002 at 50 participating medical facilities nationwide, were assessed for clinical efficacy, safety, etc. of the treatment. The total number of cases collected was 596 (479 treated with ABK, 93 with VCM and 24 with TEIC). After examination by the Review Committee for the Authenticity of MRSA Infection, 221, 203, 470 and 461 cases of the ABK treatment group, 42, 37, 86 and 87 cases of the VCM treatment group and 13, 11, 23 and 22 cases of the TEIC treatment group, respectively, were subjected to the analysis of clinical efficacy, bacteriological efficacy and safety based on the occurence of adverse reactions and safety regarding clinical laboratory test value. The clinical efficacy rates were 74.7%, 64.3% and 30.8%, the bacteriological efficacy rates were 43.8%, 35.1% and 45.5%, the occurence of adverse reactions was 5.3%, 5.8% and 13.0% and that of abnormal clinical laboratory test values was 8.7%, 8.0% and 18.2%, for the ABK treatment group, VCM treatment group and TEIC treatment group, respectively. Since the number of cases and background factors differed from group to group, the inverstigation was performed mainly with the ABK treatment group, which was the largest group. In the ABK treatment group, the first TDM was performed within 3 days after initiation of treatment in 56.9 of the cases and within 5 days after the initiation of treatment in 84.6% of the cases, with the largest cases (approximately 1/4 of entire cases) having first TDM performed on day 3 of treatment. The ABK dosing regimen was changed (dose and dosing frequency) in 45.6% of the cases under a 100 mg x 2/day regimen, which was used in the largest number of cases, and in 25.9% of those under a 200 mg x 1/day regimen (the main dose). In 77 cases with no change in the dosing regimen, the clinical efficacy rates for the 100 mg x 2/day regimen and 200 mg x 1/day regimen were 78.4% and 87.5%, respectively, and the occurence of adverse reactions was 5.5% and 5.0%, respectively. When these efficacy and safety results were analyzed by the χ² test at the 5% level of significance (two-sided), no significant difference was observed between the ABK 100 mg x 2/day regimen and the 200 mg x 1/day regimen.