Determination of methadone in human hair by radioimmunoassay.

The concentrations of methadone in human hair were measured. The washed hair was cut in 1-mm pieces approximately, then incubated overnight at 45 degrees C with 0.1 m HCl. The extracts were alcalized by 1 m NaOH and diluted by phosphate buffer, pH 7.4. The methadone concentrations were determined by radioimmunoassay. The method is simple, rapid, and practicable for routine determination.