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The time course of appearance of morphine and codeine in beard after single dose administration in two human subjects was monitored by radioimmunoassay and confirmed by gas chromatography/mass spectrometry. Both morphine and codeine appeared in beard approximately 7-8 days after drug administration at a time when drug levels in urine, plasma, and saliva were not detectable and drug-induced effects had disappeared. Drug levels in beard appeared to be dose-related suggesting that hair analysis can provide evidence of time and degree of drug exposure.
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Edward J. Cone (1990) studied this question.
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