The measurement of ofloxacin in hair as an index of exposure.

Several strands of hair were collected from each of patients who had been taking ofloxacin against bacterial infections some time in the past. In 10 out of total 14 subjects studied the drug was detected only in the hair portions corresponding to the administration period with the assumption of the hair growth rate of about 1 cm/month. Even in a subject who had received 300 mg/day of ofloxacin only for two days the drug could be detected in the corresponding portion. In 3 subjects the drug was detected in some other portion(s) than the corresponding ones. This might be due to the uncertainty of having used the drug on the other occasion. Only in one subject the dosage history could not be deduced from the drug distribution along hair length. In 3 subjects, who had taken the drug within 1 month, hair samples were collected every month for 3 or 4 consecutive months. The front of drug appearance in hair was clearly shown to move outwards along hair shaft every month at a pace of 1-1.5 cm/month. These results suggest that ofloxacin is excreted into human scalp hair, captured there and moves outwards along the hair shaft at its own growth rate. This leads to the concept that the distribution of ofloxacin along hair length can be used for knowing the individual exposure or non-exposure to the drug, and even for knowing hair growth rate when the innoculation(s) of the drug is strictly supervised and recorded.