Disclaimer: I am not a lab technician, pharmacologist, doctor, or in any way a medical professional. I am a criminal defense lawyer who sees lots of labs for drug tests, and am interested in the movement of illegal drugs through the body, and effect of illegal drugs on the body.
The most common type of drug testing are 5 panel urine tests. “5 Panel” simply refers to the five most common classes of drugs: amphetamines, methamphetamines, cocaine, marijuana, and opiates. Note that “opiates” is not a specific drug, but is rather a class of drugs that includes both, for example, heroin and Hyrdrocodone. Generally, urine tests do not determine whether the drug present is heroin or hydrocodone, but instead simply note the presence of opiates in the specimen.
To understand why 5 panel urinalysis drug tests do not specifically test for heroin, it is helpful to understand how heroin and other opioids move throughout, and are metabolized by, the body (pharmacokinetics.)
Heroin, after use, is metabolized into 6-minoacetlymorphine (6-MAM). 6-MAM is a metabolite specific to heroin, so the presence or absence of 6-MAM in a sample generally indicates heroin use, specifically. So, if a test were to examine the presence or absence of 6-MAM in a urine sample, the test could determine whether heroin, specifically, had been used. 5 panel lab tests, however, do not test specifically for 6-MAM. Even 10 panel tests do not include heroin, specifically, but do differentiate between “opiates” and “methadone,” for example.
The problem is that heroin further metabolizes from 6-MAM to morphine. Morphine is a further metabolite of heroin, and of other substances—codeine, for example, metabolizes into morphine. So the presence or absence of morphine would not be dispositive for heroin use exclusively, as it might indicate the consumption of codeine instead. And, again, whether heroin or codeine, a urine test would simply indicate the presence of “opiates.”
It is apparent then that the presence or absence of 6-MAM, as metabolite unique to heroin, yields significantly more information than the designation “opiates.” Problematically, however, 6-MAM has a very short half-life in urine (with peak levels appearing 1-4 hours after use), and is structurally similar to other opioids (e.g. codeine, oxycodone, oxymorphone, etc.) This makes urinalysis testing for 6-MAM difficult.