Propoxyphene is a synthetic opioid painkiller that appears as its own separate category on certain drug tests, most commonly the 10-panel and 12-panel screens. It was pulled from the U.S. market in 2010 after evidence showed it could cause fatal heart rhythm problems, but many drug testing panels still screen for it because some people obtain it through illicit channels or leftover prescriptions.
Why Propoxyphene Has Its Own Test Category
One of the most confusing things about propoxyphene on a drug test is that it does not show up under the general “opiates” category. Standard opiate screens detect drugs like codeine, morphine, hydrocodone, and hydromorphone. Propoxyphene has a different chemical structure, so those immunoassay tests don’t pick it up. Labs treat it as a completely separate drug class with its own screening threshold, typically 300 ng/mL.
This means a basic 5-panel drug test, which covers amphetamines, marijuana, cocaine, opiates, and PCP, will not detect propoxyphene at all. You’d need an expanded panel for it to appear.
Which Drug Tests Include Propoxyphene
The standard 5-panel test used for most federal workplace screenings does not include propoxyphene. It shows up on broader panels:
- 10-panel test: Adds propoxyphene along with barbiturates, benzodiazepines, methadone, and methaqualone to the basic five substances.
- 12-panel and extended panels: Also include propoxyphene as a standard line item.
Some employers and courts still test for propoxyphene despite its withdrawal from the market. Its presence in a sample today would suggest illicit use, since there are no legal prescriptions being written for it in the United States.
How Long Propoxyphene Stays Detectable
After someone takes propoxyphene, the liver breaks it down into a metabolite called norpropoxyphene. This metabolite is actually what labs look for during confirmation testing, because it lingers in the body longer than the drug itself. Detection windows vary by sample type:
- Urine: Up to 4 days after last use
- Hair: Up to 90 days
The 4-day urine window is a rough maximum. For a single dose, it could clear faster. For someone who used the drug repeatedly over time, it may take the full window or slightly longer to drop below the cutoff.
How the Test Works
The initial screening uses an immunoassay, a chemical reaction that flags samples above 300 ng/mL. These screening tests are designed to react to both propoxyphene itself and its metabolite norpropoxyphene. One useful detail: despite propoxyphene’s visual similarity to methadone on a chemical level, the test shows little cross-reactivity with methadone. So a positive propoxyphene result is not likely to be caused by methadone use, and vice versa.
If the initial screen comes back positive, the lab runs a confirmation test using more precise methods like gas chromatography or mass spectrometry. The confirmation specifically identifies norpropoxyphene at a cutoff of 200 to 300 ng/mL, depending on the lab. This two-step process is standard for all drug classes and exists to eliminate false positives from the initial screen.
Why It Still Appears on Drug Panels
The FDA asked all manufacturers to voluntarily pull propoxyphene products from the market in November 2010. The specific concern was that the drug could alter heart rhythms in dangerous ways, even at recommended doses. Before its withdrawal, propoxyphene was sold under brand names like Darvon and Darvocet (which combined it with acetaminophen) and was one of the more commonly prescribed painkillers in the country.
Despite being off the market for over a decade, testing panels haven’t universally dropped it. There are a few reasons. Some older stockpiles still circulate. The drug can be obtained from other countries where it may still be available. And many standardized panel configurations were designed before the withdrawal and haven’t been updated. For practical purposes, a positive propoxyphene result today raises more red flags than it would have in 2009, precisely because there’s no legitimate prescription pathway left in the U.S.
What a Positive Result Means
If your drug test comes back positive for propoxyphene, it means the lab detected norpropoxyphene in your sample above the cutoff threshold. No other common medications are known to trigger a false positive on the propoxyphene-specific assay. Unlike the general opiate screen, which can sometimes react to poppy seeds or certain cough medications, the propoxyphene test is relatively specific to that one drug and its metabolite.
Because propoxyphene is no longer legally prescribed in the United States, there is no valid prescription you could present to a Medical Review Officer to explain the result. This is a significant difference from testing positive for other opioids like hydrocodone or oxycodone, where a current prescription would typically resolve the issue.