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 multiple sclerosis, neuropathic pain, bipolar disorder, migraine prophylaxis

 

Contraindications and cautions

        Contraindicated with hypersensitivity to gabapentin.

        Use cautiously with lactation, pregnancy.

 

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 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

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; T1/2: 5–7 hr

Distribution: Crosses placenta; enters breast milk

Excretion: Urine (unchanged drug)

 

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

        Decreased serum levels with antacids

        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.