A not unusual occurrence in medicine is that while looking for one thing we find another. This happens all the time at the drug discovery level with many of our drugs being developed for one disease while looking for a cure for another disease. A classic example is the development of the tricyclic antidepressants. All the antidepressants can trace their lineage in one way or another back to isoniazid. Isoniazid was being developed as a treatment for tuberculosis. When this drug was given to severely depressed patients at state hospitals, many of the patients had a remission of their depression. As is often said, the rest is history.
With the urine drug screens we have seen another bit of medical serendipity, although not nearly to the level of importance as the above example. About one year ago the state board of medical licensure mandated point of service urine drug testing when a physician writes a prescription for benzodiazepines (Xanax, Ativan, Valium, Klonopin, etc.), opiates (oxycodone, Norco, Hydrocodone, etc.), or stimulants (Adderall, Ritalin, etc.). The reasoning that led to this decision seems to be that people that are prescribed one addictive substance such as an opiate are often prescribed another addictive substance by the same or different physician (the VA study). These patients have an increased risk of fatal drug interactions leading to respiratory depression and death. In addition, patients who are addicted to heroin or other opiates obtained either legally or illegally are often using other drugs, particularly benzodiazepines, that increases the risk of a fatal overdose.
At the time of the promulgation of these regulations, I argued strongly to the medical board that the routine urine drug testing of patients prescribed benzodiazepines was unlikely to discover patients using opiates not already noted in the PMP (a computerized data base of all controlled substances prescribed to a patient nationwide). The physician is mandated to check the PMP each time a controlled substance is prescribed. Now, about one year into this experiment some clear patterns have emerged. The first is that my reasoning regarding opiates and benzodiazepines has been confirmed. However, a totally unexpected pattern and area of concern has been manifest.
Since the institution of the above regulations, the federal government has passed the Farm Bill. In this bill was the legalization of the production of industrial hemp. In addition, proliferation of states with legalized “medical” marijuana has exploded, making marijuana products, even in states without such laws, more readily available. What we have discovered at my clinic over the past year is that the number of urine drug screens positive for opiates who had a negative PMP has been very low. However, patients positive for THC, the psychoactive component of marijuana, has been large. In addition, over the past two or three months, we have seen a dramatic rise in the number of THC positive urines who claim to have only used CBD products. Why is this clinically relevant? Please read the next blog post.