Therapeutic Drug Monitoring

To prevent drug diversion and get an accurate picture of drug usage, drug monitoring in a clinical pain management practice must test for patient compliance within specified therapeutic ranges.
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In the last few decades, pain management has pushed itself to the forefront of the healthcare industry, with approximately fifty million Americans suffering from chronic pain (The Pain Survey, Louis Harris & Associates, 1999). The prescription of powerful opiates has been an integral part of treatment; however, while offering much-needed relief for patients, these meds provide a new set of problems for physicians. Some patients fake pain in order to profit from it, often earning as much as fifty dollars or more per pill on the street. In the big picture, increased availability of painkillers can also lead to legal ramifications for clinics and their staff if lax prescribing is suspected; at the very least, it can damage a solid reputation.

The problem is not with pain management clinics themselves, which are often willing to test patients for drug diversion and compliance; it lies with the test itself. Standard drug tests aren’t good enough. Many substances prescribed for pain aren’t screened for, and most prescription concentrations fall far below the standard 2,000-ng/mL cut-off designed to detect high levels of opiates. To protect practitioners and patients alike, toxicology laboratories across the country are starting to take the next step: adjusting drug tests to specifically monitor patient compliance.

Therapeutic Drug Monitoring vs Testing for Drugs of Abuse

The two differences between therapeutic drug monitoring and testing for drugs of abuse (DOA) are simple but significant. In the former, the list of drugs is tailored to include medications most often prescribed for pain, including opiates, methadone, benzodiazepines, and fentanyl, previously undetectable in DOA testing for years. The second difference lies in the setting of the cut-off level. The 2,000-ng/mL cut-off originally set by the Substance Abuse and Mental Health Services Administration (formally known as the National Institute for Drug Abuse) is drastically reduced to 20 or 25 in a drug test for patient compliance in order to accurately detect a therapeutic range.

This customized testing method is vital for the optimization of therapy involving drugs whose desired (or toxic) effect cannot be clinically assessed. It also identifies patients who are not taking medications as prescribed or instructed.

Just as there are various reasons to monitor drug use, there are also various ways to test it, with the most popular methods depending on samples of blood and urine. For patient-compliance drug testing, both are viable options, each with its own set of pros and cons.

Blood Testing

Blood testing, the older of the two methods, normally involves an initial screen test using enzyme-linked immunosorbent assay (ELISA) technology, which combines the specificity of antibodies with the sensitivity of simple enzyme assays by coupling antibodies or antigens to an easily-assayed enzyme. This makes it possible to measure extremely low levels of drugs in solutions as whole blood, serum, urine, and tissues. ELISA results are confirmed and quantified through gas chromatography/mass spectrometry (GC/MS), regarded as the “gold standard” in drug testing for its unique combination of chromatography for separation of drugs and mass spectrometry for identification and quantization.

The biggest advantage to testing blood is its slim margin for error. Since blood can’t be adulterated, you know that you are consistently receiving accurate results. In addition, the drug levels found in a person’s blood sample directly correlate to the dosage currently present in his or her system. Therefore, the quantization level found on the report can be used to accurately calculate the amount of the drug someone is taking in, which can aid in determining if a patient’s lack of response to therapy is the result of an inadequate plasma concentration or if initial pain symptoms were brought on by drug toxicity. However, the window of detection is short; it takes only a few hours for a drug to filter through the blood, which can cause a negative result even if the patient is in compliance with their pain management regimen. This type of testing is also time-consuming and intrusive, neither of which help to keep things moving in a clinic constantly packed with patients. It’s for these reasons that urine drug testing is the method of choice most preferred by physicians.

Urine Testing

At AIT Laboratories, one of a small number of toxicology labs responding to the need for more effective drug testing in the pain management field, 95 percent of patient-compliance test samples received are urine screens. Using immunoassay or ELISA, their pain management panel (322; Comprehensive Urine Drug Screen III), screens for eleven different substances, including alcohol, amphetamines, barbiturates, benzodiazepines, cannabinoids, cocaine, fentanyl, methadone, opiates, phencyclidine, and propoxyphene. The sample’s creatinine level is also checked to determine if any adulteration has taken place. Once a substance is detected, its presence in the sample is confirmed by GC/MS; in the case of a positive barbiturate, benzodiazepine, or opiate, it will also list the specific substance present.

A urine test is not as telling as a blood test; while it can establish if a drug is present in a person’s system, it can’t determine how much. There is also a higher risk of manipulation. The dilution and concentrations factors associated with the consumption of fluid can cause drug concentrations in urine to exhibit an additional tenfold variation. However, the test’s popularity suggests that its benefits far outweigh the shortcomings.

Considerations in Drug Testing

No matter which testing method you may choose to administer, it’s more important to acknowledge that custom drug testing to confirm therapeutic use is critical to producing the most accurate readings. A common misconception about drug testing is that a negative reading is equal to a zero presence of toxins, when in truth, cut-off levels don’t monitor at a level of 0 ng/mL but one based on the individual need of the test. For example: if a person taking a low dosage of opiates to alleviate pain is submitted to a standard DOA test, the drug isn’t likely to register, as any levels falling below the 2,000 ng/mL standard won’t be detected. Since the test is only looking for levels above 2,000, it produces a negative result, which can lead one to suspect misuse on behalf of the patient. Lowering the cut-off level to 20 ng/mL tremendously improves the chances of a positive result, which is exactly what you want to see.

Insurance Reimbursement

One key distinction between standard drug tests (to ensure workplace performance) and testing for patient compliance to determine if a patient is using a prescription as prescribed (quality of health) is that the latter is likely covered by insurance. Therefore, it is important to choose a lab that not only does quality technical work, but also provides the option of third-party billing direct to insurance companies.

First published on: July 1, 2005