There seems to be some general misunderstandings as to which opiates are detected by the classic opiate assay. This is based on numerous calls from doctors, nurses, pharmacists, pain clinics, and rehab care givers that were unclear or unaware of which ‘opiates’ the classic ‘opiate screen’ will detect. Many were under the false impression that the opiate screen will pick up ‘ANY’ opiate-this is NOT the case!

To better understand this subject, it is important to remember that the screening tests all use a ‘lock and key’ type reaction, where the antibody to the drug and the drug metabolites are the lock and the key. For this reaction to occur (presumptive positive screen), the key has to fit the lock! If the key doesn’t fit the lock, it won’t open the lock-the test is negative. If the key fits the lock, you will obtain a presumptive positive screen result.

Historically, the antibody developed to detect ‘opiates’ was either codeine or morphine. Either antibody works quite well to detect the other, since codeine and morphine are structurally identical except for a tiny ‘methyl group’ that differentiates the two. Therefore a screen using a codeine antibody will detect morphine quite well-and conversely, a morphine antibody will detect codeine quite well. This is also true with the MEDTOX opiate screen.

Closely related opiates’ like hydrocodone or hydromorphone, are STRUCTURALLY different from codeine (or morphine) and the antibody designed to detect codeine (or morphine) will have a harder time ‘recognizing/detecting’ the drug because structurally it is not the same. The ‘key’ doesn’t fit the lock as well as is does for the correct drug (codeine or morphine). Thus, the screening antibody may or may not detect hydrocodone or hydromorphone. In the case of the MEDTOX opiate screen, the antibody DOES recognize hydrocodone and hydromorphone quite well—it takes a little higher level, but nothing that significant. For instance, laboratory based hydrocodone and hydromorphone screening takes approximately 800 ng/ml of drug for the 300 ng/ml opiate screen cut off, subsequently the SURE-SCREEN® onsite device has an opiate cut-off of 100 ng/ml, hydromorphone at 100 ng/mL and hydrocodone at 300 ng/mL.

As you diverge further from the codeine and morphine structure-to synthetics like oxycodone or oxymorphone, the MEDTOX Opiate antibody as well as competitor’s opiate antibodies will ultimately fail to detect their presence or if other assays do detect it, it will be at a very high concentration making the test essentially useless for detection of low levels of the drug. Therefore it is a must to use a screening test that incorporates an antibody made specifically for detecting oxycodone and its metabolite oxymorphone. The MEDTOX Oxycodone screen is designed for this purpose.

There are other drugs like fentanyl, methadone, propoxyphene, meperidine, buprenorphine, tramadol, and so forth that are thought of as “Opiates”, but they are not even remotely close to the structure of codeine or morphine. Therefore, they each require their own specific antibody and screening assay in order to detect them. MEDTOX offers our own methadone and propoxyphene screening assays. If these drugs are important to you, screening assay configurations are available with those drug options. MEDTOX also provides buprenorphine screening if this is of interest. In addition, we have lab based buprenorphine testing available also. For those needing fentanyl screening and confirmation, there are MEDTOX Lab based tests that can fulfill this need. Meperidine and Tramadol screening and confirmation are also available thru MEDTOX Laboratories.

Hopefully this information will help you make better choices of what testing to use to monitor your ‘clients’, and help you make better sense of the test results you obtain. For a full listing of what the different drug screens detect, download the product insert for the onsite device you are using and check the “Related Compounds and Cross Reactants” listing found near the end of the product insert. For additional questions, or help please consult your MEDTOX Client Service group, your sales representative, or the DARS Hotline.

Reproduced with permission from The MEDTOX® Journal