Gabapentin Blood Levels

Our pharmacist answers the latest question regarding gabapentin blood levels.

Oct 02, 2017

Tarik asked

My friend is on the drug gabapentin for side effects from chemotherapy, neuropathy in feet and in hands. she was on this for a short time but developed dizziness. she has improved greatly and wants to try again. how long does it take to achieve blood levels, to evaluate it's effectiveness?​


In general, Neuronton (gabapentin) blood levels are not monitored or checked. Blood concentration also does not necessarily correlate with effectiveness. Gabapentin is most often dosed based on the patients renal (kidney) function. 

The prescribing information for the medication does not even mention therapeutic blood levels to watch for.

Over time however, certain blood levels have been determined.

Therapeutic Concentration appears to be around 5.9-21 mcg/mL  (34.5-123 µmol/L).

Toxic Concentration appears to be around > 85 mcg/mL (> 327 µmol/L).

Again, it would be pretty rare to have blood levels drawn. Gabapentin is usually started low and titrated up to an effective dose. Below is the most common dosage for neuropathy:

Initiate therapy at 300 mg PO as a single dose on day 1, then 600 mg/day (300 mg PO twice daily) on day 2, and 900 mg/day (300 mg PO three times per day) on day 3. The dose can then be titrated up as needed for pain relief to a dose of 1800 mg/day (600 mg PO three times per day). 

In most clinical studies, efficacy was demonstrated over a range of doses from 1800 mg/day to 3600 mg/day with comparable effects across the dose range. 

​Additional benefit of using doses greater than 1800 mg/day has not been demonstrated in at least two randomized, placebo-controlled trials. ​

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