Pronunciation:

(GA ba pen tin)

U.S. Brand Names:

Generic Available:

Canadian Brand Names:

Use:

Use - Unlabeled/Investigational:

Pregnancy Risk Factor:

Pregnancy Implications:

Lactation:

Contraindications:

Warnings/Precautions:

Adverse Reactions:

>10%:

Central nervous system: Somnolence (20%), dizziness (17%), ataxia (12%), fatigue (11% in adults)

Miscellaneous: Viral infection (11% in children 3-12 years)

1% to 10%:

Cardiovascular: Peripheral edema (2%)

Central nervous system: Fever (10% in children 3-12 years), hostility (8% in children 3-12 years), somnolence (8% in children 3-12 years), emotional lability (4% to 6% in children 3-12 years), fatigue (3% in children 3-12 years), abnormal thinking (2% in children and adults), amnesia (2%), depression (2%), dizziness (2% in children 3-12 years), dysarthria (2%), nervousness (2%), abnormal coordination (1%), twitching (1%)

Dermatologic: Pruritus (1%)

Gastrointestinal: Nausea/vomiting (8% in children 3-12 years), weight gain (3% in adults and children), dyspepsia (2%), dry throat (2%), xerostomia (2%), appetite stimulation (1%), constipation (1%), dental abnormalities (1%)

Genitourinary: Impotence (1%)

Hematologic: Leukopenia (1%), decreased WBC (1%)

Neuromuscular & skeletal: Tremor (7%), hyperkinesia (3% to 5% in children 3-12 years), back pain (2%), myalgia (2%)

Ocular: Nystagmus (8%), diplopia (6%), blurred vision (4%)

Respiratory: Rhinitis (4%), bronchitis (3% in children 3-12 years), pharyngitis (3%), cough (2%), respiratory infection (2% in children 3-12 years)

Postmarketing and additional clinical reports (limited): Allergy, alopecia, angina pectoris, angioedema, anorexia, coagulation defect, erythema multiforme, ethanol intolerance, facial edema, flatulence, gingivitis, blood glucose fluctuation, subdural hematoma, hepatitis, hypercholesterolemia, hyperlipidemia, hypertension, hyponatremia, intracranial hemorrhage, jaundice, elevated liver function tests, malaise, palpitation, pancreatitis, peripheral vascular disorder, pneumonia, purpura, Stevens-Johnson syndrome, new tumor formation/worsening of existing tumors, vertigo, weakness

Overdosage/Toxicology:

Drug Interactions:

Antacids: Antacids may reduce the bioavailability of gabapentin by ~20%; gabapentin should be taken at least 2 hours following antacid administration

Cimetidine: Cimetidine may increase gabapentin serum concentrations; clearance of gabapentin is decreased by 14%

Felbamate: Serum concentrations may be increased by gabapentin; monitor for increased felbamate effect/toxicity

Morphine: Serum concentrations of gabapentin may be increased during concurrent use.

Norethindrone: Gabapentin may increase Cmax of norethindrone by 13%

Phenytoin: Phenytoin serum concentrations may be increased by gabapentin; limited documentation; monitor. Note: Valproic acid, carbamazepine, and phenobarbital do not seem to be affected by gabapentin.

Ethanol/Nutrition/Herb Interactions:

Ethanol: Avoid ethanol (may increase CNS depression).

Food: Does not change rate or extent of absorption.

Herb/Nutraceutical: Avoid evening primrose (seizure threshold decreased). Avoid valerian, St John's wort, kava kava, gotu kola (may increase CNS depression).

Stability:

Mechanism of Action:

Pharmacodynamics/Kinetics:

Absorption: 50% to 60%

Distribution: Vd: 0.6-0.8 L/kg

Protein binding: 0%

Bioavailability: As gabapentin dose increases, bioavailability decreases; it is absorbed from proximal small bowel into blood by L-amino transport system (which becomes saturated, therefore is a major contributor to lack of proportionality in plasma levels). Interpatient variability exists; standard gabapentin doses may result in different plasma concentrations in individual patients.

900 mg divided 3 times/day: 60%

1200 mg divided 3 times/day: 47%

2400 mg divided 3 times/day: 34%

3600 mg divided 3 times/day: 33%

4800 mg divided 3 times/day: 27%

Half-life elimination: 5-6 hours

Excretion: Urine (56% to 80%)

Dosage:

Children: Anticonvulsant:

3-12 years: Initial: 10-15 mg/kg/day in 3 divided doses; titrate to effective dose over ~3 days; dosages of up to 50 mg/kg/day have been tolerated in clinical studies

3-4 years: Effective dose: 40 mg/kg/day in 3 divided doses

5-12 years: Effective dose: 25-35 mg/kg/day in 3 divided doses

Note: If gabapentin is discontinued or if another anticonvulsant is added to therapy, it should be done slowly over a minimum of 1 week

Children >12 years and Adults:

Anticonvulsant: Initial: 300 mg 3 times/day; if necessary the dose may be increased using 300 mg or 400 mg capsules 3 times/day up to 1800 mg/day

Dosage range: 900-1800 mg administered in 3 divided doses at 8-hour intervals

Pain (unlabeled use): 300-1800 mg/day given in 3 divided doses has been the most common dosage range

Adults: Post-herpetic neuralgia: Day 1: 300 mg, Day 2: 300 mg twice daily, Day 3: 300 mg 3 times/day; dose may be titrated as needed for pain relief (range: 1800-3600 mg/day, daily doses >1800 mg do not generally show greater benefit)

Elderly: Studies in elderly patients have shown a decrease in clearance as age increases. This is most likely due to age-related decreases in renal function; dose reductions may be needed.

Dosing adjustment in renal impairment: Children 12 years and Adults: See table.

Hemodialysis:

Neurontin Dosing Adjustments in Renal Impairment

Administration:

Monitoring Parameters:

Reference Range:

Test Interactions:

Dietary Considerations:

Patient Education:

Anesthesia and Critical Care Concerns/Other Considerations:

Dental Health: Effects on Dental Treatment:

Dental Health: Vasoconstrictor/Local Anesthetic Precautions:

Dosage Forms:

Capsule (Neurontin®): 100 mg, 300 mg, 400 mg

Solution, oral (Neurontin®): 250 mg/5 mL (480 mL) [cool strawberry anise flavor]

Tablet: 100 mg, 300 mg, 400 mg

Neurontin®: 600 mg, 800 mg

Extemporaneously Prepared:

Triturate sixty-seven 300 mg tablets in a mortar, reduce to a fine powder, then add a small amount of one of the following vehicles to make a paste; then add the remaining vehicle in small quantities while mixing:

Vehicle 1. Methylcellulose 1% (100 mL) and Simple Syrup N.F. (100 mL) mixed together in a graduate, or

Vehicle 2. Ora-Sweet® (100 mL) and Ora-Plus® (100 mL) mixed together in a graduate

Shake well before using and keep in refrigerator

Nahata MC, Morosco RS, and Hipple TF, Stability of Gabapentin in Extemporaneously Prepared Suspensions at Two Temperatures, American Society of Health System Pharmacists Midyear Meeting, December 7-11, 1997.

International Brand Names: