gabapentin

gabapentin

(gab ah pen' tin)

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 posttetanic 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—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; 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

Creatinine clearance (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; T_1/2: 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.

Adverse effects in Italic are most common; those in Bold are life-threatening.