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

Scenario: Uncovering Illicit Use of Gabapentinoids in a Patient with Several Comorbidities

Conditions addressed
chronic pain and muscle spasms, anxiety, Barrett’s esophagus/GERD, PTSD-related sleep disturbance, treated opioid use disorder

Medications addressed
buprenorphine, hydrocodone, alprazolam, quetiapine, pantoprazole, venlafaxine, gabapentin, pregabalin

Image: iStock

Patient Case
A 54-year old Caucasian male, 5’10” tall and weighing 200 lbs, presents with chronic neck and shoulder pain. He has a muscular build and shares that he lifts weights with a professional trainer at least 3 times per week. He is unable to tolerate nonsteroidal anti-inflammatory drugs (NSAIDs) due to Barrett’s esophagus following an initial diagnosis of GERD 5-plus years ago and has a history of Helicobacter pylori negative gastrointestinal bleed. The patient also has a history of opioid use disorder (OUD), following acute pain management subsequent to a major motor vehicle accident 6 years prior that left him hospitalized for 4 months with fractures to the right hip, both wrists, and right ulna. He continues to suffer from residual bone pain from the accident and remains on chronic opioid therapy. He has a Patient Agreement with the practice and his compliance is monitored closely; he has not displayed any drug aberrancy for at least 3 years.

Other medical problems in this patient include general anxiety disorder and chronic and intermittent muscle spasms. He has post-traumatic stress disorder (PTSD) from the motor vehicle accident which impairs his sleep.

Overall, the patient’s medication regimen consists of:

  • buprenorphine buccal film, 450 mcg Q12H for chronic pain
  • hydrocodone/acetaminophen, 5/325 mg PO TID PRN pain
  • alprazolam, 0.5mg PO BID each day, and 1 extra tablet daily only if needed for anxiety and/or muscle spasms
  • quetiapine, 50 mg PO QHS for PTSD and sleep
  • pantoprazole, 40 mg PO daily for Barrett's esophagus and GERD
  • venlafaxine XR, 225 mg PO QAM for pain and depression

Presumptive Drug Monitoring Results

On routine follow-up visit, his nurse practitioner (NP) ordered a standard presumptive (also known as preliminary or qualitative) urine screen. (Read about the 2 main types of urine drug monitoring tests.) Table I shows the results.

 

In viewing the presumptive test results, the NP was concerned that this patient was opiate and buprenorphine negative while receiving prescriptions for buprenorphine and hydrocodone; positive for methadone, tetrahydrocannabinol (THC), and phencyclidine (PCP); and also negative for benzodiazepine although receiving regularly scheduled alprazolam.

Discussion with Patient and Lab Leads to More Detail

Patient Compliance

The NP discussed the preliminary results with the patient and gave him a chance to explain potential reasons for the findings. The patient shared that he had been taking his hydrocodone, buprenorphine, and alprazolam regularly even though the tests were negative. He denied use of methadone, PCP, and THC.

At this point, the NP explained to the patient that she would call the lab to discuss the initial findings and that she would likely need to order further definitive (also known as confirmatory or quantitative) testing to confirm compliance. She documented the conversation and justification for definitive testing.

Weighing the Presumptive Screen Results

In this particular case, which can present frequently in pain management, it is important to consider what may be expected, versus unexpected, when reviewing panel screen results. See Tables II and III.

 

*See a related case scenario on drug monitoring in patients on MAT

 

The NP contacted the testing laboratory to discuss the presumptive findings, and the laboratory’s recommendation was consistent with her hunch that definitive testing would be an appropriate next step. Specifically, the laboratory confirmed the following:

  • alprazolam is often not picked up in an immunoassay benzodiazepine screen (immunoassay is the presumptive testing method commonly used by laboratories)
  • quetiapine may cause a false-positive for methadone
  • buprenorphine has a high cut-off and may not be detected in IA testing
  • hydrocodone at the doses prescribed may not be positive for opiates
  • venlafaxine may test false-positive for PCP

Overall, it was likely that the patient was, in fact, compliant, but to confirm this, definitive testing was ordered. The NP followed up with the patient to share her findings and explained why she was ordering more testing as the best course of action - with the definitive results, his chart could reflect his compliance. (See a related video on how to share drug monitoring results with a patient.)

She gave the patient a 1-week supply of medications and ordered a comprehensive definitive screen, via liquid chromatography-mass spectrometry (LC-MS), that included the panel above as well as other common substances of abuse.

Definitive Drug Monitoring Results

One week later, the definitive testing results were in, as shown in Table III.

In examining the definitive screen results, it seemed that, although the patient was compliant with his prescribed medications, as suspected, there was an unexpected finding of methylphenidate and gabapentinoids (specifically gabapentin and pregabalin).

Course of Action

The NP spoke with the patient about the definitive screen results at his follow-up visit. She complimented him for his honesty and compliance regarding his prescribed medications. She then asked him to comment on the unexpected finding of both pregabalin and gabapentin, plus methylphenidate.  He stated that he did not mention those medications because he was not specifically asked about them, and that he was afraid that she would discontinue his other prescriptions. He explained that since his accident, he had been working hard to keep up his shape and build muscle mass. He reported that the methylphenidate gave him the energy boost he needed to complete intensely harder and longer workouts, and that the gabapentinoids served to relax him later in the day. He admitted to using high doses of gabapentin (1200 to 1800 mg) at once or pregabalin (up to 900 mg), both of which individually caused a numbing sensation. He further reported that he was using high doses of natural testosterone supplements but that, occasionally, he was able to obtain injectable anabolic steroids. Each of these was secured illicitly.

The NP was very uncomfortable continuing this patient’s buprenorphine, hydrocodone, and alprazolam. She ordered an alprazolam taper, discontinued the hydrocodone, and continued the buprenorphine and quetiapine. She made it clear to the patient that the latter 2 prescriptions were going to be prescribed one week at a time and were contingent on him seeing a behavioral health specialist as well as physical therapist. She explained the risks of obtaining illicit drugs and their potential toxicities with and without the drugs she was prescribing. She reminded him of his Patient Agreement on file and further explained that continued use of gabapentinoids and/or methylphenidate or anabolic steroids would result in immediate cessation and/or taper of his pain medications. She also ordered more frequent drug monitoring (once per month) going forward.

Key Takeaways

  • Several factors, beyond patient behavior, may contribute to identifying patients who may be at risk for noncompliance, abuse, misuse, and/or diversion.
  • Prescribing clinicians need to understand the drug complexity involved in interpreting urine drug monitoring screens, including the differences between presumptive and definitive testing, and potential harm to the patient and/or treatment plans if results are misinterpreted. Read more about why drug monitoring is pertinent in primary care, behavioral care, and specialty care.
  • If a patient is misusing or abusing controlled substances, explaining the risks involved and referring that patient for professional help is more likely to have a positive outcome than automatically discontinuing a controlled substance, as the latter might encourage the patient to seek illicit sources. Together, early detection and transparency may save a patient’s life.

 

Written by Jeffrey Fudin, PharmD, DAIPM, FCCP, FASHP, FFSMB. 
The case presented herein is hypothetical and the views presented do not represent those of the authors’ employers, the VA, or any federal agency. Disclosure: Dr. Fudin serves as a medical advisor to Quest Diagnostics.

Last updated on: May 5, 2020
Continue Reading:
Scenario: Finding THC in Test Results for a Patient on Opioids and NSAIDs
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