Classifications: anticonvulsant; gaba analog; Therapeutic: anticonvulsant
Pregnancy Category: C
100 mg, 300 mg, 400 mg capsules; 100 mg, 300 mg, 400 mg, 600 mg, 800 mg tablets; 250 mg/5 mL solution
Gabapentin is a GABA neurotransmitter analog; however, it does not interact with GABA receptors, and it does not inhibit GABA
uptake or degradation. Mechanism of action is unknown.
Used in conjunction with other anticonvulsants to control certain types of seizures in patients with epilepsy. Effective in
controlling painful neuropathies.
Adjunctive therapy for partial seizures with or without secondary generalization in adults, post-herpetic neuralgia.
Add-on therapy for generalized seizures, peripheral neuropathy, migraine prophylaxis.
Hypersensitivity to gabapentin; pregnancy (category C), lactation. Safety and efficacy in infants and children <3 y are not
Status epilepticus, renal impairment, older adults.
Route & Dosage
|Adjunctive Therapy for Seizure Disorder
Adult/Child (>12 y): PO Start 300 mg on day 1, 300 mg b.i.d. on day 2, 300 mg t.i.d. on day 3, and continue to increase over a week to an initial
total dose of 400 mg t.i.d. (1200 mg/d); may increase to 18002400 mg/d depending on response (most patients receive
9001800 mg/d in 3 divided doses) 400 mg t.i.d. (1200 mg/d)
Child (312 y): PO Start 1015 mg/kg/d in 3 divided doses, titrate q3d to target dose of 40 mg/kg/d in pts 34 y or 2535 mg/kg/d
in pts ≥5 y in 3 divided doses
Adult: PO Start 300 mg day 1, 300 mg b.i.d. day 2, and 300 mg t.i.d. day 3; may increase up to 600 mg t.i.d. if needed
Clcr >60 mL/min: 400 mg t.i.d.; 3060 mL/min: 300 mg b.i.d.; 1530 mL/min: 300 mg q.d.; <15 mL/min: 300 mg q.o.d.
Hemodialysis: 200300 mg following dialysis
- Adjust dosage for patients with creatinine clearance of 60 mL/min or less. See manufacturer's recommendations.
- Separate doses of gabapentin and antacids by 2 h.
- Withdraw drug gradually over 1 wk; abrupt discontinuation may cause status epilepticus.
- Store at 15°30° C (59°86° F); protect from heat, moisture, and direct light.
Adverse Effects (≥1%)CNS: Drowsiness, fatigue,
dizziness, tremor, slurred speech, impaired concentration, headache, increased frequency of partial seizures. Endocrine:
Weight gain. GI:
Nausea, gastric upset, vomiting. Special Senses:
Blurred vision, nystagmus. Skin:
Increase in phenytoin
levels at higher doses (300600 mg/d gabapentin). Does not affect serum levels of other anticonvulsants
reduce absorption of gabapentin. Herbal: Ginkgo
may decrease effectiveness.
5060% from GI tract. Peak:
Peak level 13 h; peak effect 24 wk. Distribution:
Crosses the bloodbrain barrier; readily passes into cerebrospinal fluid; not bound to plasma proteins; highest concentrations
found in pancreas and kidneys. Metabolism:
Does not appear to be metabolized. Elimination:
7681% unchanged in 96 h; 1023% recovered in feces. Half-Life:
Assessment & Drug Effects
- Monitor for therapeutic effectiveness; may not occur until several weeks following initiation of therapy.
- Assess frequency of seizures: In rare cases, the drug has increased the frequency of partial seizures.
- Assess safety: Vision, concentration, and coordination may be impaired by gabapentin.
Patient & Family Education
- Learn potential adverse effects of drug.
- Notify physician immediately if any of the following occur: increased seizure frequency, visual changes, unusual bruising
- Do not drive or engage in other potentially hazardous activities until response to drug is known.
- Do not abruptly discontinue use of drug; do not take drug within 2 h of an antacid.