Gabapentin, Serum or Plasma

CPT: 80171
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Test Details


  • Neurontin®


Liquid chromatography/tandem mass spectrometry (LC/MS-MS)

Reference Interval

4.0−16.0 μg/mL

Additional Information

Gabapentin (Neurontin®) is an oral antiepileptic agent that is structurally related to the neurotransmitter γ-aminobutyric acid (GABA) but it does not interact with GABA receptors in the brain. Its mechanism of action is unknown but it has properties in common with other anticonvulsant medications. Gabapentin is only 3% bound to circulating protein in the blood and is not appreciably metabolized. Gabapentin is cleared by the kidneys and has an elimination half-life of five to seven hours.1 Steady-state concentrations are reached after one to two days with the time between ingestion and maximal serum concentration being two to three hours.2 For therapeutic drug monitoring, specimens should be drawn as trough levels. There are no significant drug interactions with other anticonvulsants. Adverse reactions are not common and are confined to somnolence (1.2%), ataxia (0.8%), fatigue (0.6%), nausea or vomiting (0.6%), and dizziness (0.6%).

Specimen Requirements


Serum or plasma


1 mL

Minimum Volume

0.3 mL


Red-top tube, lavender-top (EDTA) tube, or green-top (heparin) tube. Do not use a gel-barrier tube. The use of gel-barrier tubes is not recommended due to slow absorption of the drug by the gel. Depending on the specimen volume and storage time, the decrease in drug level due to absorption may be clinically significant.


Transfer separated serum or plasma to a plastic transport tube.

Storage Instructions

Maintain specimen at room temperature.

Stability Requirements



Room temperature

14 days


14 days


14 days

Freeze/thaw cycles

Stable x3

Causes for Rejection

Gel-barrier tube

Clinical Information


1. Drug Facts and Comparisons. 66th ed. St Louis, Mo: Wolters Kluwer Co; 2012.
2. Bourgeois BF, “Pharmacokinetic Properties of Current Antiepileptic Drugs. What Improvements Are Needed?” Neurology. 2000; 55(11 Suppl 3):S11-S16. 11147563


Order Code Order Code Name Order Loinc Result Code Result Code Name UofM Result LOINC
716811 Gabapentin (Neurontin), Serum 9738-6 716812 Gabapentin, Serum ug/mL 9738-6

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