In this case scenario, I discuss gabapentin and renal function. A 77-year-old female has a history of neuropathy, CHF, GERD, OA, and anxiety. She reports that she feels more sedated of late and that she can’t attend her usual BINGO games and has also had a hard time finding the energy to volunteer as she has previously done. In addition to feeling like she could sleep all the time, she has noted that her legs feel like they have more fluid than they used to despite no reported change in diet and fluid intake. She’s wondering what might be causing this?
Labwork drawn today includes:
- Potassium 4.4 mEq/L
- Sodium 136 mEq/L
- Creatinine 2.3 mg/dL
- eGFR 18 mls/min
- Hemoglobin 11.9 mg/dL
- TSH – WNL
Her current medication list includes:
- Lisinopril 40 mg daily
- Metoprolol XL 25 mg daily
- Aspirin 81 mg daily
- Acetaminophen 500 mg BID
- Duloxetine 30 mg daily
- Gabapentin 600 mg TID
- Furosemide 20 mg daily
- Lorazepam 0.25 mg TID PRN
- Pantoprazole 40 mg daily
With the sedation and worsening edema, one must look at the use of gabapentin. These are both potential side effects of this medication. Likely exacerbating the risk of this adverse effect is the 1800 mg daily dose in a 77-year-old. Another consideration that is likely to contribute to gabapentin’s adverse effects is this patient’s renal function. With this creatinine and eGFR, the dose should have been reduced to a recommended maximum of 600 mg per day. This risk for adverse effects goes up significantly when considering gabapentin use and renal function changes.
Another consideration that should not be overlooked is the lorazepam use. Although it is a very low dose, adding a benzodiazepine on top of a medication like gabapentin can significantly increase the risk for sedation. Inquiring whether or not the lorazepam PRN is being taken is also an important assessment in this case.
My initial sense would be to reduce the gabapentin at least in half to 300 mg TID and then likely down to a max of 600 mg per day. If neuropathy becomes an issue, increasing the duloxetine might be a consideration. Another option to consider is if any topical agents have been tried.
It would be important to also have previous lab reports. Specifically, I would like to know what the previous creatinine and eGFR were to compare to the current value we have now. What else would you look at in this situation?
Here’s another clinical pearl regarding gabapentin effectiveness and how this drug’s absorption can vary based upon the dose.
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