Fentanyl is a potent synthetic opioid that acts on the same brain receptors as other opioids like morphine. It is considerably stronger than many common opioids, being 50 to 100 times more potent than morphine and 30 to 50 times more potent than heroin. Even a dose as small as two milligrams can be fatal. Because of its high potency, fentanyl is sometimes mixed with other illicit drugs, often without the user’s knowledge, leading to accidental overdoses. Hair follicle analysis is a method to detect such substances.
How Drugs Enter Hair
Drugs enter the hair through a biological process once consumed and circulating in the bloodstream. Blood vessels surround hair follicles, structures beneath the skin where hair grows. Drugs and their metabolites, breakdown products, transfer from the blood into these follicles. Substances also reach the hair through sweat and oil glands on the scalp, diffusing into the hair shaft as it forms. Once incorporated, these substances become trapped within the hair as it grows, providing a record of past drug exposure.
Fentanyl’s Hair Detection Window
Hair follicle tests offer a longer detection window for substances like fentanyl compared to other methods. Fentanyl and its metabolites can typically be detected in hair for up to 90 days, or three months. This extended detection period is due to the average growth rate of head hair, about half an inch per month. Hair tests commonly analyze the first 1.5 inches of hair closest to the scalp to cover this 90-day timeframe. While drug use may not appear in the hair until 7 to 10 days after exposure, once incorporated, it remains, making hair testing valuable for assessing patterns of use over time.
Variables Affecting Detection
Several factors can influence how long fentanyl remains detectable in hair. The amount and frequency of fentanyl use are significant; higher doses or more frequent use typically result in greater drug concentrations. Individual metabolic rates also play a role, as physiology affects how quickly the drug is processed. Hair growth rates can vary slightly among individuals, potentially altering the exact 90-day window.
Hair color can influence detection, as some drugs and their metabolites bind more readily to melanin, the pigment in hair. This can lead to higher concentrations in darker hair compared to lighter hair for the same dosage. External factors, such as certain hair treatments, may also affect drug concentrations. Hair treatments like bleaching or dyeing can reduce drug concentrations by damaging the hair shaft, but substances ingrained within the hair are generally not completely removed.
Hair Test Reliability and Other Considerations
Hair follicle tests are recognized for their high accuracy in detecting drug use. Laboratories typically employ a two-step process, starting with a rapid screening method and confirming presumptive positive results with precise techniques like mass spectrometry. No test is entirely without potential for false results. False positives are uncommon but can occur from external contamination, such as environmental exposure. False negatives might arise if insufficient drug was consumed or use occurred outside the detection window.
If a person has insufficient head hair for a sample, body hair can be used for testing. Samples can be collected from areas such as the armpit, chest, or legs. Body hair generally grows slower than head hair, which means it may provide a longer detection window, potentially up to 12 months, but the timeframe for detection is less precise. The sample collected is typically a small lock of hair, about the thickness of a pencil, cut close to the scalp.