Gabapentin: Mechanism of action not understood; antiepileptic activity may be related to its ability to inhibit polysynaptic responses and block post tetanic potentiation.

Generic Name

gabapentin

Brand Name

Apo-Gabapentin (CAN), Gen-Gabapentin (CAN), Neurontin

Pregnancy Category C

Drug class

Antiepileptic

Therapeutic actions

  • Mechanism of action not understood; antiepileptic activity may be related to its ability to inhibit polysynaptic responses and block post tetanic potentiation.

Indications

  • Adjunctive therapy in the treatment of partial seizures with and without secondary generalization in adults and children 3–12 yr with epilepsy
  • Orphan drug use: Treatment of amyotrophic lateral sclerosis
  • Management of postherpetic neuralgia or pain in the area affected by herpes zoster after the disease has been treated
  • Unlabeled uses: Tremors of MS, neuropathic pain, bipolar disorder, migraine prophylaxis

Contraindications and cautions

  • Contraindicated with hypersensitivity to gabapentin.
  • Use cautiously with pregnancy, lactation.

Available forms

Capsules—100, 300, 400 mg; tablets—100, 300, 400, 600, 800 mg; oral solution—250 mg/5 mL

Dosages

ADULTS

  • Epilepsy: Starting dose is 300 mg PO tid, then titrated up as needed. Maintenance: 900–1,800 mg/day PO in divided doses tid PO; maximum interval between doses should not exceed 12 hr. Up to 2,400–3,600 mg/day has been used.
  • Postherpetic neuralgia: Initial dose of 300 mg/day PO; 300 mg bid PO on day 2; 300 mg tid PO on day 3.

PEDIATRIC PATIENTS 3–12 YR

Initially, 10–15 mg/kg/day PO in three divided doses; adjust upward over about 3 days to 25–35 mg/kg daily in three divided doses in children > 5 yr, and up to 40 mg/kg/day in three divided doses in children 3–4 yr.

GERIATRIC PATIENTS OR PATIENTS WITH RENAL IMPAIRMENT

Cr/Cl (mL/min) Dosage (mg/day)
> 60 900–3,600 in three divided doses
> 30–59 400–1,400 in two divided doses
> 15–29 200–700 in one dose
< 15 100–300 in one dose

Postdialysis supplemental dosing, 125–350 mg PO following each 4 hr of dialysis.

Pharmacokinetics

Route Onset Duration
Oral Varies 6–8 hr

 

Metabolism: Hepatic; T1/2: 5–7 hr

Distribution: Crosses placenta; enters breast milk

Excretion: Urine, unchanged

Adverse effects

  • CNS: Dizziness, insomnia, nervousness, fatigue, somnolence, ataxia, diplopia, tremor
  • Dermatologic: Pruritus, abrasion
  • GI: Dyspepsia, vomiting, nausea, constipation, dry mouth
  • Respiratory: Rhinitis, pharyngitis
  • Other: Weight gain, facial edema, cancer, impotence

Interactions

Drug-drug

  • Decreased serum levels with antacids

Drug-lab test

  • False positives may occur with Ames N-Multistix SG dipstick test for protein in the urine

Nursing considerations

Assessment

  • History: Hypersensitivity to gabapentin; lactation, pregnancy
  • Physical: Weight; T; skin color, lesions; orientation, affect, reflexes; P; R, adventitious sounds; bowel sounds, normal output

Interventions

  • Give drug with food to prevent GI upset.
  • Arrange for consultation with support groups for people with epilepsy.
  • WARNING: If overdose occurs, hemodialysis may be an option.

Teaching points

  • Take this drug exactly as prescribed; do not discontinue abruptly or change dosage, except on the advice of your health care provider.
  • Wear a medical alert ID at all times so that any emergency medical personnel will know that you have epilepsy and are taking antiepileptic medication.
  • You may experience these side effects: Dizziness, blurred vision (avoid driving or performing other tasks requiring alertness or visual acuity); GI upset (take drug with food or milk, eat frequent small meals); headache, nervousness, insomnia; fatigue (periodic rest periods may help).
  • Report severe headache, sleepwalking, rash, severe vomiting, chills, fever, difficulty breathing.

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