Gabapentin (Neurotnin) is an antiepileptic drug with a unique mechanism of action that enhances nonsynaptic release of gamma aminobutyric acid GABA) release. Although originally approved for treating epilepsy, this drug is more commonly used for treatment of chronic pain. Gabapentin is not metabolized and does not bind to plasma proteins. Parent drug is excreted by the kidneys. No serious or idiosyncratic effects have been identified. Most common side effects are mild sedation, nausea, behavioral changes, movement disorders, and weight gain.
The recommended initial dose is 300 mg daily. The dosage can be increased at 300 mg intervals daily up to 900 to 4800 mg per day. The circulating half life is 5 to 7 days in patients with normal renal function. Gabapentin is eliminated almost entirely by the kidneys. A wide range of serum concentrations, from 2.0 to 20 ug/mL have been associated with effective seizure control.
Gabapentin can be measured by enzyme immunoassay or tandem mass spectrometry. Therapeutic range is 2.0-20.0 ug/mL. Levels of 25.0 ug/mL or greater may be toxic.
Trough levels should be drawn one hour before the next dose.
Specimen requirement is one plain red top tube or one lavender top (EDTA) tube.
References
Mao J, Chen L, Gabapentin in Pain Management, Anesthesia Analgesia, 2000;91(3):680-687.
Rose MA, Kam PCA, Gabapentin: pharmacology and its use in pain management, Anaesthesia, 2002; https://doi.org/10.1046/j.0003-2409.2001.02399.x
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