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29 May 2026
As part of Labcorp’s commitment to providing evolving drug testing solutions to improve patient outcomes, we continuously survey urine samples for designer opioids. As an ongoing process, we sequester a subset of clinical urine samples for advanced research testing. Urine samples that screen positive for 6-acetylmorphine (an active metabolite of heroin) are de-identified and subjected to further testing looking for the presence of fentanyl, fentanyl analogs, and other designer opioids and related compounds.
Historic trends of some of the main compounds of interest are displayed in Figure 1, highlighting the shifting landscape of polydrug use combining heroin with designer opioids and other adulterants.
Key takeaways
- As the presence of medetomidine rises in fentanyl-positive urine samples, xylazine detection has declined from historical peaks, potentially indicating a shift in sedative adulteration practices within the illicit opioid supply
- Fentanyl analogs, including acetyl fentanyl and fluorofentanyl, remain present but at lower and more variable levels, indicating a reduction in analog diversity within the fentanyl supply. Fentanyl itself continues to be the primary opioid detected, often in combination with non-opioid compounds
- Carfentanil, the highly potent fentanyl analog, has reemerged after being essentially absent in 2021 and 2022. This notoriously lethal fentanyl analog is now detected in >10% of fentanyl-positive samples
- This information is constantly evolving, and we expect to see fleeting drug trends as illicit markets adapt. Observing novel designer opioids and pharmacologically active adulterants (such as xylazine and medetomidine) in the absence of fentanyl is very rare. The presence of illicit fentanyl generally indicates that additional adulterants or novel substances may be or are likely present even if not individually tested
Figure 1: Detection history of the most common designer opioids and adulterants found in heroin-positive samples.