Neuropathy Case Study – A Medication Adverse Effect

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RS is a 62-year-old male with a history of type 2 diabetes, hypertension, atrial fibrillation, and metastatic colorectal cancer. He presents to the clinic with complaints of numbness, tingling, and burning pain in both feet that have been gradually worsening over the past three months. He states the pain is worse at night and interferes with his sleep. He denies recent alcohol use or toxin exposure. In this neuropathy case study, we will identify the most important medication-related issues to assess.

Metformin 1000 mg BID
Lisinopril 20 mg daily
Gabapentin 300 mg TID (started for neuropathic pain, only partial relief)
Warfarin (dosed per INR)
Omeprazole 20 mg daily
Bortezomib IV q2 weeks (for cancer treatment)
Acyclovir 400 mg BID (prophylaxis)
Furosemide 40 mg daily
Levofloxacin 500 mg daily × 10 days (for pneumonia)

In ruling out causes of neuropathy, chemotherapeutic agents are always important to review. Bortezomib is a medication with a decent incidence of causing neuropathy, and this would likely be my top culprit. A dose reduction or review for a possible alternative would be a great place to start.

Metformin and omeprazole are known to contribute to B12 deficiency (excellent board exam nugget). Neuropathy is a potential complication of B12 deficiency, and this should be ruled out as well. The length of metformin and PPI use is also an important thing to assess. Drawing a B12 level will be helpful in identifying if this is a concern.

The other medication I would focus on in this neuropathy case study is levofloxacin. It has been associated with neuropathy and would be a consideration in this case. It appears the neuropathy has been gradually worsening over the last three months, so this would be my least likely choice of the three that would cause neuropathy.

The last thing I would want to assess is diabetes control. Diabetic neuropathy is certainly a possibility here and shouldn’t be overlooked.

What other concerns do you have with this case?

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