Time course of appearance of cotinine in human beard hair after a single dose of nicotine

The time course of appearance of cotinine in saliva and in daily collections of beard clippings was monitored by gas chromatography with mass spectrometry in six volunteers who were nonsmokers following a single 30-min buccal administration of nicotine as a chewing gum. Salivary cotinine concentrations reached a plateau after 1.5 h and were nondetectable (< 0.3 ng/ml) 24 h after drug administration. Cotinine was detected in extracts of sodium hydroxide digests of beard hair in all subjects on the third day after drug administration. Mean concentrations in beard peaked on day 5, and cotinine was not detected (< 0.03 ng/mg) after day 7. The data indicate the main route for cotinine incorporation into beard is during hair growth. Transfer into beard from sweat is of little importance. A role for transfer via sebum is equivocal.