What the SAMHSA-5 federal workplace panel actually tests for

The single most common drug test in the United States is the federal 5-panel urine screen, sometimes called the SAMHSA-5 or NIDA-5. It is the test used by federal agencies, federally regulated workplaces, Department of Transportation employers, and most private employers who model their programs on the federal standard. According to the Substance Abuse and Mental Health Services Administration’s 2017 Mandatory Guidelines for Federal Workplace Drug Testing Programs, the panel screens for exactly five classes of substances:

Ketamine is not on this list. It is not a cannabinoid, not a stimulant, not an opiate, and not phencyclidine. Although ketamine and PCP belong to the same chemical family of arylcyclohexylamines and share dissociative effects, they are pharmacologically and structurally distinct, and the immunoassay antibodies used in standard PCP screens are designed to detect PCP specifically. A standard SAMHSA-5 result will not flag therapeutic ketamine.

Prescription ketamine is a Schedule III controlled substance under federal law, which means it is recognized as a legitimate medication with accepted medical use. When you receive ketamine therapy at a licensed clinic, you are using it lawfully as prescribed. Ketamine is FDA-approved as an anesthetic; its use for depression, anxiety, PTSD, and chronic pain is off-label. The Schedule III status and the off-label framing both matter when you are talking to an employer, a medical review officer, or a prescribing clinician about your treatment.

When ketamine does get tested for: extended panels and forensic settings

While ketamine is excluded from the standard federal panel, it can be detected when a lab is specifically asked to look for it. The most common scenarios where this happens:

If you are unsure which panel your employer uses, ask HR or your occupational health contact. Employers are generally willing to confirm what their lab tests for, and it costs nothing to ask before a scheduled test.

Pharmacokinetics: how the body processes ketamine and norketamine

To understand detection windows, it helps to know what happens to ketamine after a clinic infusion. Ketamine is metabolized primarily in the liver by cytochrome P450 enzymes—chiefly CYP3A4, CYP2B6, and CYP2C9—into norketamine, its principal active metabolite. Norketamine is then further metabolized into hydroxynorketamine and other downstream compounds, all of which are excreted in urine.

The FDA-approved Spravato (esketamine) prescribing information from Janssen reports that esketamine, the S-enantiomer of ketamine and the only FDA-approved psychiatric form, has a mean elimination half-life of approximately 7 to 12 hours after intranasal administration. Norketamine’s half-life is generally longer than ketamine’s, which is part of why the metabolite is the more useful detection target in urine. After a single therapeutic dose, the parent compound clears relatively quickly while norketamine lingers.

This is the basis for the way labs configure ketamine assays. Confirmatory testing by gas chromatography-mass spectrometry (GC-MS) or liquid chromatography-tandem mass spectrometry (LC-MS/MS) typically targets both ketamine and norketamine, with norketamine providing the wider detection window. Cutoffs vary by lab, but the SAMHSA-style logic of an immunoassay screen followed by mass-spectrometry confirmation is standard practice.

Detection windows: urine, blood, saliva, hair

The forensic literature on ketamine detection is built primarily from controlled-dose studies, post-mortem cases, and recreational-use samples. Adamowicz and Kala, writing in Forensic Science International (2005), characterized urinary detection of ketamine and norketamine and reported windows that have held up across subsequent research.

Approximate detection windows after a single therapeutic dose:

These are general ranges. Individual factors—dose, frequency, hydration, kidney function, body composition, and lab cutoff thresholds—all shift the numbers. Research suggests that high-dose or repeated infusion protocols can extend the urinary window to a week or longer in some patients. Studies indicate that hair analysis sensitivity scales with cumulative exposure rather than single-dose pharmacokinetics.

PCP cross-reactivity: the rare false positive question

A recurring concern from patients is whether ketamine will trigger a false positive on the PCP portion of the standard 5-panel. This is documented in the older literature but uncommon on modern, well-designed immunoassays. Both compounds are arylcyclohexylamines, which is why the cross-reactivity exists at all, but contemporary PCP antibodies are reasonably specific.

If a PCP screen does come back non-negative and you have no PCP exposure, the situation is solvable. The lab’s confirmatory mass-spectrometry step distinguishes ketamine and norketamine from PCP without ambiguity. The Medical Review Officer process, described below, is also designed to resolve exactly this kind of result.

What to do if you are subject to drug testing

If your work or licensure involves drug testing, treat your ketamine therapy the same way you would treat any prescription medication that could affect a panel.

For patients who use HSA, FSA, or self-pay routes, the documentation we provide for superbills doubles as MRO-friendly documentation in most cases. Tennessee’s clinic regulations are also worth understanding if your employer requests details about the setting; we have written about Tennessee ketamine clinic regulations separately.

The MRO process: how legitimate medical use is verified

The federal workplace drug-testing system is built around the Medical Review Officer, a licensed physician trained in substance-abuse review who interprets every non-negative result before it reaches the employer. The SAMHSA Medical Review Officer Manual (DHHS, 2010) spells out how this works.

When a lab reports a non-negative result, the MRO contacts the donor directly and asks whether there is a legitimate medical explanation. If the donor produces evidence of a valid prescription or current treatment, the MRO verifies it with the prescribing provider and reports the result to the employer as negative. The employer never sees the underlying analyte; they see only the final adjudicated result.

For ketamine specifically, the MRO will typically ask for:

This process exists because the federal system recognizes that legitimate Schedule III prescription use is not workplace drug abuse. Our patients have used the MRO process without difficulty when they have brought documentation forward proactively. Understanding the FDA framework around ketamine can also help you talk through Schedule III status and off-label use with an MRO who is less familiar with the territory.

Safety-sensitive roles deserve a final word. CDL drivers, commercial pilots under FAA Part 67, federal employees in covered positions, and certain healthcare licensees operate under additional medication review processes that go beyond the basic MRO step. Some of these programs require advance notification, periodic check-ins with a designated medical examiner, or specific timing of treatment relative to duty. Our safety overview and our safety page describe how we think about clinical monitoring; what they do not cover is the regulatory side. Talk to your employer’s occupational medicine contact and your prescribing clinician before you start. We will work with whatever process your role requires.

Ketamine is FDA-approved as an anesthetic; its use for depression, anxiety, PTSD, and chronic pain is off-label. Evidence supports its careful use for these conditions in appropriate patients, and the testing question is one piece of the broader conversation about whether ketamine therapy fits your situation. We are happy to walk through it with you.