The measurement of a new antimicrobial quinolone in hair as an index of drug exposure.

1. Scalp hair samples were obtained at 1 month intervals up to 5 months from healthy male volunteers participating in a phase I study of a new antimicrobial quinolone, OPC-17116. 2. Hair was sectioned into 1 cm lengths from the scalp end. Corresponding portions from five pieces of hair were dissolved in 1 N NaOH and assayed for OPC-17116 by h.p.l.c. 3. In all subjects taking a single dose (400 mg, n = 5) or repeated doses (400 mg day-1, twice daily, for 6.5 days, n = 6), the drug was detected in the portions of hair corresponding to the administration period, assuming a hair growth rate of 1 cm/month. 4. OPC-17116 (300 mg day-1, three times daily, for 2 days) was given to four healthy male volunteers, from whom hair samples were obtained at 1 month and 3 months. The drug was detected in 1 to 4 consecutive 2.5-mm long portions of a single hair and there was no significant axial diffusion of the agent along the hair shaft with time. 5. These findings indicate the utility of measuring this quinolone derivative in hair as an index of exposure, and as a time-marker for the hair analysis of other drugs.