Measurement of Temafloxacin in Human Scalp Hair as an Index of Drug Exposure

□ Scalp hair samples were obtained at 1-month intervals up to 3 months from healthy male volunteers participating in a phase I study of a new antimicrobial quinolone, temafloxacin. Hair was sectioned into 1-cm lengths from the scalp end. After corresponding portions from 10 pieces of hair were dissolved in 1N NaOH, temafloxacin was extracted by chloroform and measured by HPLC equipped with fluorescence detection (excitation and detection wavelengths, 280 and 460 nm, respectively). In all subjects taking a single oral dose (600 mg; n = 6) or repeated oral doses (900 mg/day, b.i.d., for 6.5 days; total, 5850 mg; n = 6), the drug was detected in hair. The 1-cm length of hair, in which temafloxacin was peaked, was shown to move at the rate of 1 to 1.3 cm/month when the hair of growing stage was analyzed. The largest sum of the concentrations of temafloxacin found in any set of measurements in hair in each subject was 31.7 ± 15.0 (mean ± SD, n = 6) and 226.3 ± 99.4 ng/mg hair (n = 6) for the single and repeated doses, respectively. The drug concentration in hair increased by a factor of 7.1, whereas the ratios between the single and repeated doses were 9.8, 1.3, and 10.7 for the total given dose, observed maximal plasma concentration (Cmax). and area under the plasma concentation curve, respectively. It was obvious that the was the least likely factor determining temafloxacin concentration in hair. The utility of measuring temafloxacin in hair was indicated as an index of exposure to the drug and as a time marker for the analysis of other drugs in hair.