Immunoassay evidence for fentanyl in hair of surgery patients

Head hair samples obtained from surgery patients who received fentanyl during anesthesia were analyzed by immunoassay for the presence of fentanyl. Thirteen hair samples were collected from patients following intravenous administration of 1-6 mg of fentanyl. Additional hair samples were collected following the administration of 0.18 and 0.38 mg of sufentanil to 2 patients. The elapsed time after drug administration for all patients ranged from 7 to 273 days. Twenty control hair samples also were collected from staff members who reported no surgery or anesthesia during the previous year. All samples were initially washed with methanol, followed by extraction with methanol and reconstitution in citrate buffer. Analysis of wash and extract fractions was performed by radioimmunoassay (Coat-A-Count Fentanyl assay). Segmental analysis was performed on the surgery patients' hair samples. Eight of the fentanyl patients' hair samples contained fentanyl concentrations (equivalents) of 0.13-0.48 ng/10 mg of hair in the 'root' end. Fentanyl concentrations in the 'tip' segment were lower than those found in the 'root' segment with the exception of 1 subject whose hair sample had been collected only 7 days after surgery. The remaining 5 patients had fentanyl concentrations similar to those determined for the control subjects hair samples (0-0.08 ng/10 mg, n = 19). No correlation between hair fentanyl concentration and administered dose was found for the 13 fentanyl subjects. Both sufentanil subjects' hair samples tested negative. One control subject who had experienced environmental exposure to fentanyl had a fentanyl concentration of 0.29 ng/10 mg in the extract and 0.63 ng/10 mg in the wash fraction. Overall, it was concluded that hair analysis for fentanyl provided convincing evidence of past exposure to the drug.