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General Rehabilitation

Concurrent High Dose Gabapentin and Opioid Use Leading to Neurologic Toxicity in Inpatient Rehabilitation: A Case Report

Friday, October 24, 2025
12:00 PM - 1:30 PM MT
Location: Kiosk 1

    Primary Author(s)

  • Benjamin Hoste, MD

    Resident Physician
    McGaw Medical Center of Northwestern University (SRAL) PM&R Program
    Chicago, Illinois

    • Co-Author(s)

  • SH

    Stephanie Hendrick, MD

    Attending Physician, Assistant Professor
    Shirley Ryan AbilityLab
    Chicago, Illinois

Disclosure(s):
Benjamin Hoste, MD: No financial relationships to disclose
Case Diagnosis: A 45-year-old female with metastatic breast cancer to the bone presented to an Inpatient Rehabilitation Facility (IRF) after a pathologic T6 fracture.

Case Description or Program Description: During acute hospitalization, the patient started on methadone 5 milligrams (mg) three times daily, gabapentin 800 mg three times daily, Tylenol 1000 mg every 6 hours as needed, and hydromorphone 6 mg every 3 hours as needed. During IRF admission, she reported worsening pain despite increasing hydromorphone frequency. On day 13, she began experiencing brief episodes of full-body jerking, blinking, and visual hallucinations. Sudden involuntary jerking of her arms and legs was witnessed during therapy.

Setting: IRF

Assessment/Results: The patient’s symptoms were thought to be myoclonus and hyperalgesia due to medication-induced neurotoxicity. She had been taking 200 morphine milliequivalents (MME) per day in addition to 2400 mg of gabapentin. Palliative care was consulted, and her gabapentin was reduced to 600 mg three times daily, methadone continued, and hydromorphone was switched to morphine IR 15 mg every 3 hours as needed. This regimen resulted in better pain control with 110 MME per day. Within 48 hours, her myoclonus and hallucinations resolved.

Discussion (relevance): Opioid-induced neurotoxicity may be seen in patients on high dose opioids for cancer pain. Gabapentin-induced neurotoxicity has been described in the literature, although often in patients with renal dysfunction, which this patient did not have. It is not infrequent that patients in inpatient rehabilitation will need increased doses of pain medication given their high level of activity during therapy. It is important to monitor for neurotoxicity in IRF patients on escalating high doses of opioids and neuropathic agents. Treatment often involves reducing opioid and/or gabapentin doses.

Conclusions: In inpatient rehabilitation, cancer patients on escalating opioid doses and high-dose gabapentin who develop new neurologic symptoms should be evaluated for neurotoxicity. Dose reduction can paradoxically improve pain control and resolve neurologic symptoms.