Naltrexone Drug Test Guide: Panels, Detection Windows & More
Evidence-based answer reviewed against SAMHSA cutoffs and FDA assay documentation · Updated August 2026
Quick answer: Opioid antagonist — not included on the federal 5-panel. Urine detects it roughly 1–3 days (oral); injectable releases for weeks; hair archives ~90 days; saliva and blood track only recent use. Never screened on standard panels; specialized adherence monitoring exists in treatment programs.
Overview
This guide covers everything verifiable about how testing handles Naltrexone (also searched as: opioid blockers): which panels include it, detection windows across specimens, cutoff levels, false-positive risks, and legitimate prescription handling.
Panel membership
| Panel | Naltrexone status |
|---|---|
| 5-Panel | ❌ Not included |
| 10-Panel | ❌ Not included |
| 12-Panel | ❌ Not included |
| DOT 5-panel (safety-sensitive) | ❌ Not included |
Detection windows
| Test type | Typical Naltrexone detection window |
|---|---|
| Urine | any: 1–3 days (oral); injectable releases for weeks |
| Saliva (Mouth Swab) | any: ~1 day |
| Hair Follicles | rare |
| Blood | any: ~1 day |
Cutoff levels
Never screened on standard panels; specialized adherence monitoring exists in treatment programs.
Cutoffs exist to separate real use from noise — dietary exposure, passive contact and legacy medications stay below them by design. Screen-above-cutoff results still require mass-spec confirmation before reporting.
Deep-dive facts
Naltrexone blocks opioid receptors rather than activating them — it's the opposite of an opioid in screening terms and appears nowhere on employment panels. Treatment programs may monitor levels to verify adherence to monthly injections.
Legal status note
Rx, unscheduled.
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Naltrexone Drug Test Guide: Panels, Detection Windows & More?
Complete Naltrexone drug test guide: which panels detect it, urine/hair/saliva/blood detection windows, cutoff levels and prescription verification. Full guide →
How accurate are drug tests?
Lab-based immunoassay screens agree with confirmation testing ~97% of the time; confirmed GC–MS results are considered definitive. Home kits trade legal defensibility for convenience.
Do prescriptions count against me?
No — verified prescriptions report as negative through the Medical Review Officer. Declare medications at collection and answer the follow-up call.
Sources & further reading
- SAMHSA — Mandatory Guidelines for Federal Workplace Drug Testing Programs (cutoffs, MRO process)
- DOT — 49 CFR Part 40 procedures for transportation workplace testing
- Brahm NC et al., Mayo Clinic Proceedings 2008;83(1):66–76 — false-positive cross-reactivity reference
- FDA — drug-of-abuse test device labeling (detection window conventions)