Of course we all know that cannabis metabolites show nothing about one’s current impairment and will remain in one’s system for weeks or months following cessation of use. We’ve talked about the perverse incentive this creates to use alcohol and other toxic addictive drugs that clear from one’s system in two to three days. And now, this information from the American Psychiatric Association leads me to better understand why we’re seeing such an uptick in prescription drug abuse.
NEW ORLEANS — That poppy seeds can lead to false-positive results on tests for opioid abuse is not just an urban legend, researchers said [at the American Psychiatric Association's annual meeting last May].
Another example is that most standard drug tests don’t screen for the opioid drug oxycodone, as well as a handful of other opioids including methadone and fentanyl, noted Smith, who conducted the research while he was at Boston Medical Center.
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Opioid tests screen for morphine and codeine, which are two of the most common metabolites of many — but not all — opioids. They’re not metabolites of oxycodone, methadone, fentanyl, tramadol (Ultram), and buprenorphine (Subutex, Suboxone), Smith said.
Similarly, only certain metabolites of benzodiazepines are detected on most assays. That means diazepam, nordiazepam, and oxazepam (Serax) will be detected, but alprazolam (Xanax), lorazepam (Ativan), and clonazepam (Klonopin) aren’t frequently screened.
In their review, the researchers found that drug tests generally have a sensitivity of 90% to 95%, and a specificity of 85% to 90%. These numbers are a “pretty good basis” for making clinical decisions, Smith said, but that means “one in 20 [tested patients] are going to have inaccurate results, and those are more likely to be false positive than false negative.”
Many substances aside from poppy seeds cause these false-positives. Cold medications can give a positive read on amphetamines, as can bupropion (Wellbutrin) and tricyclic antidepressants.
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Sertraline (Zoloft) and oxaprozin (Daypro) can alert physicians to a benzodiazepine problem when there is none.
The HIV medication efavirenz (Sustiva) can come up as a positive for marijuana use, and dextromethorphan, rifampin, and quinolones could show as an opioid problem.
There is a Jackson’s Food Store – a gas station / convenience store chain out West – that is two blocks from my home. I walk my dog there every day as I pick up my fountain Diet Coke refill for lunch. I’ve gotten to speak with most of the employees about marijuana – my pot leaf hat leads to lots of these conversations. One of the kids pumping gas there is a sweet young man who is a migraine sufferer whom I’ve told would be a shoo-in for a medical marijuana card.
Then one day recently I notice that there are a whole bunch of new workers. I find out that the store had come up $1,800 short in an audit, so in response, Jackson’s was drug testing all their employees. Three employees admitted to occasional marijuana use and now they are unemployed. There is no evidence that any of them were filching cash from register and since the firings the shortages from the till haven’t ceased. But Jackson’s feels better, I guess, for having some scapegoats to blame.
Ironically, the one young man who could really use medical marijuana still has his job. ”I only toke a tiny bit and only if the pain is just unbearable,” he told me, “because I just can’t lose this job – I have to take care of my wife and kid. Luckily I hadn’t had a bad migraine for a few weeks, so I was able to pass the test.” Even if he had a medical marijuana card, his job wouldn’t be protected. My wife, a migraine patient herself, volunteered that her regular use of cannabis has turned what used to be weekly migraines to seasonal migraines – maybe four a year – and when they do come, they are moderate and not “drill a hole in my head” painful like before.
Now some would say, “Well, they knew the rules on drug testing; they don’t have to work there.” Keep in mind that Portland, Oregon is suffering some >10% unemployment. And then try to imagine your life if finding aspirin or ibuprofen or acetaminophen or naproxen in your system meant the end of your job and you have a splitting headache.