Chronic pain affects tens of millions of people in the United States, and according to the Centers for Disease Control, in 2016, prescribers wrote 66.5 opioid and 25.2 sedative prescriptions for every 100 Americans. “These are sobering statistics,” says F. Leland McClure, PhD, MSci, F-ABFT, director, medical science liaison, medical affairs, Quest Diagnostics. Dr McClure notes that there are multiple reasons for this high statistic, including an increase in chronic diseases among an aging population, and a decreased tolerance for pain among Americans in general.
Relieving that pain is an important medical goal, one undertaken by primary care physicians and pain specialists alike. Opioids are the most commonly used class of prescription drugs, with central nervous system depressants second in line. “Anti-anxiety medications can also be an important part of pain management,” he noted, “since anxiety about pain can be significant for some patients.”
But fulfilling that important medical goal comes with risk—of prescription drug abuse, diversion, and combining prescribed and nonprescribed or illicit drugs. “Prescription drug abuse can happen anywhere,” Dr McClure said, “and can happen to anyone, including patients who receive pain medications for migraines, sports injuries, root canals, or chronic back problems.”
Diversion often begins at home
Diversion is a major cause of new pain medication addiction, and it often doesn’t involve sales between strangers. “It can start in the bathroom medicine cabinet,” he said. One study from 2008 showed that over 55% of those who used nonprescribed painkillers originally got them for free from a friend or relative. “We all know someone with the best of intentions who shares their medication.” Veterinary medications can also be diverted.
“Physicians who prescribe controlled medications have a responsibility to make sure the patient is taking the drug he has been prescribed, is not passing the drug on to others, and is not taking other drugs, legal or illegal, that have not been prescribed,” Dr McClure stressed. Urine drug testing is a central tool in performing this vital task.
“Urine provides the longest timeline for detection of drugs and drug metabolites,” Dr McClure noted. While drugs and metabolites may last only a day or less in blood and oral fluids, they persist for an average of 4 days in urine, extending the window for obtaining relevant results.
Screen, then confirm
Testing can include both screening (presumptive) and confirmatory (definitive) testing. Screening can identify a class of drugs, such as opiates, but cannot identify specific drugs or their metabolites. “Just detecting the drug class doesn’t provide you with distinct information to understand what drug or metabolites are actually present,” Dr McClure said, but it does provide a first-pass look at the patient’s drug use. It can also provide a test of the validity of the sample, for instance whether it has been diluted with water after collection. “This can be important in the high-risk population that may be tested.”
“But confirmatory testing is always recommended,” he emphasized. Mass spectrometry, the basis of most confirmatory tests, “is still the gold standard. It identifies exactly which drug or metabolite is in the sample, distinguishing for instance between hydrocodone and morphine” —a distinction that is impossible with a screening test.
Interpretation of results is just as important as ordering the tests in the first place, Dr McClure stressed. There are several important things that results can’t tell the physician. Quoting Douglas Gourlay, author of Urine Drug Testing in Clinical Practice, he said “There is no scientifically validated relationship between the amount of drug taken and urine drug concentration. Therefore, UDT cannot indicate the amount of drug taken, when the last dose was administered, or the source or form of the drug.” Believing or assuming that results can provide such information “may put patients and/or physicians at medical or legal risk.”
In addition, “Positive results are not going to tell you whether the patient is impaired, or addicted, or physically dependent,” Dr McClure noted. Negative results may mean the patient has never taken the prescribed drug, or has not taken it as prescribed, or may have an enhanced or decreased metabolism of the drug for genetic reasons. The test results can be the start of a conversation, but should not be the end of one.
Quantitative reporting is essential
Quantitative reporting of results—getting the actual values, not just whether they are above or below a cut-off—is recommended, both by the Department of Health and Human Services and the Center for Medicare and Medicaid Services. “This provides the ability to distinguish between a borderline cut-off and something that is grossly elevated,” Dr McClure said.
For instance, if a patient has been prescribed a high level of codeine, the urine may contain enough hydrocodone to surpass the cut-off. This is because hydrocodone is a minor metabolite of codeine, and doesn’t necessarily mean the patient is taking the drug. “Quantitative testing is utilized to identify if hydrocodone is a minor metabolite of codeine. We don’t want a patient unfairly penalized for hydrocodone showing up,” he said. Similarly, high levels of prescribed morphine can generate trace amounts of hydromorphone that can be picked up on a urine drug screen, “so it’s very important to do quantitative reporting to establish near-cutoff or minor metabolites.”
More information on these topics and a complete web-based presentation can be found here.
Published date: Aug. 24, 2018
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