GabapentinPA study guide
Known brand names include Neurontin.
An anticonvulsant taken by mouth. It eases nerve pain after shingles (postherpetic neuralgia) and is added to other seizure medicines for partial onset seizures.
Known brand names include Neurontin.
An anticonvulsant taken by mouth. It eases nerve pain after shingles (postherpetic neuralgia) and is added to other seizure medicines for partial onset seizures.
Labeled use. Adjunctive therapy for partial onset seizures in adults and children 3 years and older.
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A good choice for neuropathic pain such as postherpetic neuralgia or diabetic neuropathy, and as an add-on for focal seizures, when few drug interactions are wanted: it is not metabolized by the liver and does not affect other antiepileptic levels. It is weak as monotherapy for epilepsy. Avoid or use cautiously with opioids, in COPD, or in patients with substance misuse history. Requires renal dose adjustment.
The exact mechanism is unknown. Gabapentin is structurally related to GABA but does not act on GABA binding, uptake, or breakdown. It binds tightly to the alpha-2-delta subunit of voltage-gated calcium channels. It is not metabolized and is cleared unchanged by the kidneys, with a half-life of 5 to 7 hours.
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The label does not describe a narrow therapeutic index or direct dosing by measured blood levels of the drug.
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Doses come from the FDA label. Study tool, not for clinical decisions.
Required. By creatinine clearance (mL/min): 60 or more, 900 to 3600 mg/day in three doses; above 30 to 59, 400 to 1400 mg/day in two doses; above 15 to 29, 200 to 700 mg/day once daily; 15, 100 to 300 mg/day once daily, and below 15 reduce in proportion. On hemodialysis, add a supplemental dose of 125 to 350 mg after each 4 hours of dialysis.
None needed. Gabapentin is not metabolized, so it was not studied in hepatic impairment.
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None on the current Neurontin label. Respiratory depression with opioids and other CNS depressants is a labeled warning.
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No specific antidote. Overdose causes double vision, slurred speech, drowsiness, lethargy, and diarrhea; fatal respiratory depression has occurred, especially with other CNS depressants. Give supportive care. Hemodialysis removes gabapentin.
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Published studies have not shown a higher risk of major birth defects or miscarriage, though they have limits. Animal studies showed fetal harm. Use with opioids near delivery may raise the risk of neonatal withdrawal. A pregnancy registry for antiepileptic drugs exists.
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Gabapentin passes into breast milk. Effects on the breastfed infant and on milk supply are unknown; weigh the benefits of breastfeeding against the mother's need for the drug.
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Partial seizures from age 3: start 10 to 15 mg/kg/day in three doses and titrate over about 3 days to 40 mg/kg/day (ages 3 to 4) or 25 to 35 mg/kg/day (ages 5 to 11). Not established below age 3 or for postherpetic neuralgia. Watch for behavior changes such as hostility and hyperactivity.