Fentanyl is detectable in urine for 24 to 72 hours, in blood for up to 48 hours, in saliva for 1 to 4 days, and in hair for up to 90 days.
Detection windows extend significantly with chronic use due to fentanyl’s accumulation in adipose tissue. Standard five-panel immunoassay screens do not reliably detect fentanyl because its synthetic phenylpiperidine structure d...