Last Updated: July 28, 2022

By Emanuel Sferios and Rachel Clark

It has come to our attention that the most recent batch of BTNX brand fentanyl testing strips is more sensitive to false positives when testing MDMA and methamphetamine. If you purchased strips from us in October or November of 2021 (or from any other test strip supplier), look at the packaging each strip comes in. 

• If you have lot #DOA2105196, you will need to dilute MDMA and methamphetamine more than the recommended amount that we specify in our instructions. Rather than the standard 2mg/ml, you will need to dilute down to 0.5mg/ml.
  • This is 10mg of crushed powder into 4 teaspoons (20ml) of water.
  • Not diluting down to this ratio could result in a false positive for fentanyl.
• If you have lots #D808009, DOA093194 or DOA2105207 we have received reports that these older batches of strips may also require this larger dilution. We recommend using the 0.5mg/mL dilution detailed above (10mg of powder per 4tsp of water) with these lots as well.

For cocaine, ketamine and most other drugs, we continue to recommend a higher dilution of 10mg/ml (100mg of powder per TWO teaspoons of water).

Note: The strips work fine other than this extra sensitivity to MDMA and methamphetamine.

Recap:

• Testing MDMA or methamphetamine: 
  • If you have one of the aforementioned lots of test strips, the dilution is 10mg of MDMA/meth into 4tsp of water. That’s 4x the amount of water you’d normally use when testing MDMA/meth.
  • If you have any other batch of test strips, the dilution is 10mg of MDMA/meth into 1tsp of water.
  • Pressed pill reminder: Testing pressed pills (“pressies”) of MDMA with fentanyl test strips will yield unreliable results. Pressed pills contain an unknown quantity of MDMA relative to binder material. They might also contain other drugs in addition to MDMA, which generally can’t be determined without lab testing. This means that it is usually not possible to dilute a pressed MDMA tablet correctly to avoid false positives while also making sure you don’t dilute so much that you miss any fentanyl that might be present.
• Testing most other drugs:
  • Use the standard dilution of 100mg of powder per 1tsp of water, regardless of which batch of strips you have.

After extensive dialogue, BTNX (the manufacturer of the strips) has assured us that they will begin testing the false positive sensitivity of each new batch of strips prior to distributing them to the harm reduction community. Furthermore, going forward we will be working with some research laboratories around the country to conduct our own tests on street samples of MDMA and meth using each new batch of strips. Variations in batch sensitivity should no longer be an issue with these new measures in place, and our original recommended dilution of 2mg/ml (10mg per teaspoon of water) for meth and MDMA will continue to work. 

Lastly, if you are concerned that a recent positive test result with meth or MDMA may be false, please email eman@dancesafe.org. Include the methods you used in the test and the lot number of the strip if you have it.