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 1 N 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 (C_max), and area under the plasma concentation curve, respectively. It was obvious that the C_max 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.