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It has been proposed that administration of a reliable marker substance to human subjects may enhance the ability to identify drug use and treatment compliance in drug treatment programs. The goal of this study was to determine if an oral dose of the antibiotic ofloxacin (OFLX) could be used as a "marker" substance to establish reference points with respect to time in hair of various colors. Male and female subjects (n = 32) between 18 and 40 years of age received 800 mg of OFLX as a divided oral dose on a single day. Subjects were restricted from cutting their hair or performing chemical treatments. Hair was collected (by cutting) before, and at weeks 4, 5, 6, and 7 after drug administration. Subjects were classified as having black (n = 5), brown (n = 13), blonde (n = 8), or red (n = 6) hair. Hair was segmented into 3.0-cm segments prior to digestion, extraction, and analysis by high-pressure liquid chromatography (HPLC). At 7 weeks, the mean OLFX concentrations (+/- 1 SD) in the first 3.0 cm of hair closest to the scalp were as follows: 30.6 +/- 8.5 ng/mg (black), 6.0 +/- 1.8 ng/mg (brown), 3.5 +/- 1.6 ng/mg (blonde), and 1.4 +/- 0.3 ng/mg (red). A similar pattern was found in hair collected at weeks 4-6. Quantitative eumelanin (EUM) hair concentrations for each subject were also determined for each subject via HPLC. A strong relationship between OFLX concentration at 7 weeks and EUM was noted (r2 adjusted = 0.728; p &lt; 0.001). In six subjects, we also determined the intrasubject variability of OFLX incorporation into individual hair strands. Four strands from each subject were segmented into 2-mm segments and analyzed. OFLX appeared in segments #1-#10 at week 5 (the first centimeter of hair). OFLX appeared in segments #2-#20 at week 7 (the first and second centimeter of hair). The maximum OFLX concentration (the "band" of drug) and location was then determined for each strand. The maximum OFLX concentration was measured in segments #2-#5 at week 5 for all subjects (within the first centimeter of hair length). The maximum OFLX concentration was measured in segments #3-#8 at week 7 (within the first and second centimeter of hair). This was consistent with a growth rate of less than 1.0 cm/month, although considerable intersubject variability was found. No significant axial diffusion of OFLX along the hair shaft beyond the first 3.0 cm of hair was noted. Despite a strong effect of hair color, these data suggest that OFLX may be a suitable marker substance for hair, allowing a subject to serve as their own "control". Future studies will explore whether drug use, treatment compliance, or recidivism in clinical drug-abuse studies can be determined with the aid of OFLX.

Ofloxacin as a Reference Marker in Hair of Various Colors