Clinical Drug Monitoring in Primary Care
Brought to you by Quest Diagnostics and Practical Pain Management

How and What to Monitor

How to Share Clinical Drug Monitoring Results with Your Patient with Jeff Gudin, MD

The conversation presented is simulated based on clinical experience.

Clinical drug monitoring should be utilized as part of a universal risk-management strategy when controlled substances are prescribed. It is not a one-time process, but rather, a protocol that should be integrated into the standard treatment plan for any patient that is prescribed controlled medication.

Drug monitoring is most commonly performed using a urine specimen. If a patient is unable to produce a urine specimen, oral fluid may be used. Urine is the preferred, cost-effective, non-invasive, specimen that provides a longer window for monitoring drug use.

There are two main types of urine monitoring tests: Presumptive and Definitive.

Presumptive Drug Monitoring
Presumptive drug monitoring identifies possible use or non-use of drugs or drug classes and includes lab-based immunoassay and point-of-care methods. Results are expressed qualitatively, as negative or presumptive-positive, and cannot distinguish true-positive from false-positive results. Additionally, presumptive testing may not be available for some of the commonly used and potentially misused medications such as tramadol, tapentadol, and gabapentin.

Presumptive drug monitoring tests are used to provide:

  • quick, initial qualitative results via laboratory immunoassay
  • screening of a large number of drugs or drug classes at once.

Definitive Drug Monitoring
Definitive drug monitoring identifies specific drugs and metabolites, and can confirm presumptive results or rule out presumptive false-positives. While definitive testing is more specific, it is also more costly. Therefore, best practices can include presumptive testing first and confirming unexpected negatives or positives with definitive testing. This two-step approach can help reduce over-testing and balances good clinical care with cost.

Definitive drug monitoring tests are used to:

  • confirm presumptive positive results by identifying specific drugs and drug metabolites
  • rule out false-negative results when presumptive testing lacks sensitivity
  • identify specific drugs or substance present in the sample.

In some cases, definitive testing may be the only test option if presumptive testing is not available for a certain drug (eg, tapentadol).

How to order drug monitoring tests for patients

Drug monitoring can be ordered as selections that are individualized to the patient, such as opiates, benzodiazepines, and amphetamines (see list below for examples of common drug classes). Monitoring can also be used to identify use of unexpected drugs or illicit substances such as cocaine, heroin, and other synthetic or designer drugs.

Common drug class tests may include, but are not limited to: alcohol, amphetamines, barbiturates, benzodiazepines, cocaine, fentanyl, heroin, marijuana, methadone, opiates (eg, codeine, hydrocodone, hydromorphone, morphine), and oxycodone. (Source: Using Urine Drug Testing (UDT) to Monitor Opioid Therapy for Chronic Non-Cancer Pain. Interagency Guideline on Prescribing Opioids for Pain, Washington State Agency Medical Director’s Groups (AMDG), 3rd Edition, June 2015.)

In specific cases, additional tests may be selected to include medications such as: carisoprodol, gabapentin, pregabalin, tapentadol, tramadol, zolpidem, methylphenidate or its metabolite ritalinic acid.

For more information about drug monitoring options, please refer to the menu listing from Quest Diagnostics.

To determine what drugs to test for, consider the following:

  • Is this a baseline monitoring test for a new patient where a broader list of tests may be appropriate?
  • What prescription medications, not prescribed by me, may pose a safety risk if taken with medications that I prescribed?
  • What tests were performed previously (for existing patients) and what results were expected versus unexpected?
  • What illicit substances should I consider based on the patient’s history, clinical presentation, and/or community usage? (see also, Who to Monitor)

Some common examples of what to test for:

Safe Use of Prescription Medications: Detection of Illicit Drugs: Detection of Other Substances:
  • benzodiazepines
  • gabapentinoids
  • opioids
  • muscle relaxants
  • cocaine
  • heroin
  • marijuana
  • methamphetamine
  • synthetic/designer drugs (eg, bath salts, spice)
  • alcohol
  • fentanyl
  • nicotine


How to interpret results

Your diagnostics laboratory can help explain a patient’s urine drug test results, if needed. If you interpret the results on your own, it is important to have a basic understanding of the metabolism of controlled substances. For example:

  • Morphine is metabolized into hydromorphone in very small amounts. For the morphine-prescribed patient, hydromorphone-positive results may be misinterpreted as supplementation with non-prescribed drug.
  • Non-modified immunoassays (IAs) for benzodiazepines may demonstrate low cross-reactivity for lorazepam and clonazepam and these may not be detected.

If presumptive-positive or presumptive-negative results seem questionable, you may order a definitive test to confirm if the drugs or substances are present.

Key Takeaways
  • Urine is the most common specimen used for monitoring drug use and there are two main types of tests: Presumptive and Definitive
  • Best practices can include a two-step approach of presumptive testing first, followed by definitive testing. Definitive drug monitoring tests identify the drug(s) or substance(s) present in the specimen. This process can help reduce over-testing and balances good clinical care with cost.
  • Drug monitoring tests should be ordered as medically necessary to manage the patient.

 

Next, Additional Resources, including downloadable FAQs for your patients

 

Last updated on: April 30, 2019
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