An assessment of the routes of incorporation of opiates into beard hair after a single oral dose of codeine.

The time course of appearance of immunoreactive opiates was monitored in saliva, sweat, and beard hair in six healthy whites who were not opiate users after oral administration of 60 mg of codeine phosphate. The opiate concentration in saliva peaked within 30 min of drug administration and returned to near the predose level within 24 h. Ninety-one percent of the total secretion of opiates in sweat was collected by the skin-collection patch worn during the first 24 h after drug administration. Detectable material was also present in sweat patches on the following 2 days. Opiates were detected in extracts of alkali digests of beard hair in all subjects on the day after drug administration. Hair concentration peaked on day 3 after dosing and then decreased continuously until day 8. From day 8 until the end of the experiment on day 14, beard hair contained opiate concentrations significantly greater than the predose level. From comparison with cotinine pharmacokinetics, it is proposed that an early and the largest transfer of opiates into beard hair is through sweat. Transfer during hair growth is secondary and of comparable importance to a newly identified contribution of long duration that may involve transfer from storage depots within skin.