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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 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 post-herpetic 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 as needed. Maintenance: 900–1,800 mg/day PO in divided doses tid PO; maximum time between doses should not exceed 12 hr. Up to 2,400–3,600 mg/day has been used. Post-herpetic 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 3 divided doses; adjust upward to 25–35 mg/kg daily in 3 divided doses in children > 5 yr, and up to 40 mg/kg/day in 3 divided doses in children 3–4 yr. GERIATRIC PATIENTS OR PATIENTS WITH RENAL IMPAIRMENT Creatinine clearance (mL/min) > 60 > 30–59 > 15–29 < 15
Dosage (mg/day) 900–3600 in 3 divided doses 400–1400 in 2 divided doses 200–700 in 1 dose 100–300 in 1 dose
Postdialysis supplemental dosing, 125–350 mg PO following each 4 hr of dialysis.
Pharmacokinetics Route Oral
Onset Varies
Duration 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
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. 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. These side effects may occur: 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.
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 post-herpetic 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 as needed. Maintenance: 900–1,800 mg/day PO in divided doses tid PO; maximum time between doses should not exceed 12 hr. Up to 2,400–3,600 mg/day has been used. Post-herpetic 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 3 divided doses; adjust upward to 25–35 mg/kg daily in 3 divided doses in children > 5 yr, and up to 40 mg/kg/day in 3 divided doses in children 3–4 yr. GERIATRIC PATIENTS OR PATIENTS WITH RENAL IMPAIRMENT Creatinine clearance (mL/min) > 60 > 30–59 > 15–29 < 15
Dosage (mg/day) 900–3600 in 3 divided doses 400–1400 in 2 divided doses 200–700 in 1 dose 100–300 in 1 dose
Postdialysis supplemental dosing, 125–350 mg PO following each 4 hr of dialysis.
Pharmacokinetics Route Oral
Onset Varies
Duration 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
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. 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. These side effects may occur: 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.
