Gabapentin

Indications

Gabapentin is used for: Epilepsy, Neuropathic pain, Partial Seizures, Hot flashes, Fibromyalgia, Postherpetic Neuralgia, Pain from diabetic neuropathy.

Adult Dose

Partial Seizures Adjunctive therapy for partial seizures with or without secondary generalization Initial: 300 mg PO q8hr May increase up to 600 mg PO q8hr; up to 2400 mg/day administered and tolerated in clinical studies; up to 3600 mg administered for short duration and tolerated Postherpetic Neuralgia Day 1: 300 mg PO qDay Day 2: 300 mg PO q12hr Day 3: 300 mg PO q8hr Maintenance: Subsequently titrate as needed up to 600 mg PO q8hr; doses >1800 mg/day have demonstrated no additional benefit Restless legs syndrome 100-300 mg PO 2 hr before bedtime on first day; may titrate every 2 weeks until symptom relieve achieved (range 300-1800 mg/day) Diabetic Neuropathy 900 mg/day PO initially; may increase gradually q3Days to 1800-3600 mg/day Hot flashes-cancer related 200-1600 mg PO qDay to q6hr for 4-8 weeks

Child Dose

Partial Seizures Adjunctive therapy for partial seizures with or without secondary generalization in patients older than 12 years of age with epilepsy; also indicated as adjunctive therapy for partial seizures in pediatric patients aged 3-12 years <3 years: Safety and efficacy not established 3-12 years (initial dose): 10-15 mg/kg/day PO divided q8hr initially; titrate up in approximately 3 days to effective maintenance dose 3-4 years (maintenance dose): 40 mg/kg/day PO divided q8hr 5-12 years (maintenance dose): 25-35 mg/kg/day PO divided q8hr >12 years (initial dose): 300 mg PO q8hr; may increase up to 600 mg PO q8hr

Renal Dose

Renal impairment CrCl >60 mL/min: 300-1200 mg PO TID CrCl 30-60 mL/min: 200-700 mg q12hr CrCl 15-29 mL/min: 200-700 mg qDay CrCl <15 mL/min: 100-300 mg qDay Hemodialysis (CrCl <15 mL/min): Administer supplemental dose (range 125-350 mg) posthemodialysis, after each 4 hr dialysis interval; further dose reduction should be in proportion to CrCl (eg, CrCl of 7.5 mL/min should receive one-half daily posthemodialysis dose)

Administration

May be taken with or without food.

Contra Indications

Hypersensitivity. Lactation.

Precautions

Discontinuation or transfer from other antiepileptics, history of psychotic illness; renal impairment; pregnancy. Gradual withdrawal over at least 7 days to prevent an increase in seizure frequency. Lactation: Enters breast milk; use with caution

Pregnancy-Lactation

Interactions

May increase plasma level w/ morphine. Reduced absorption w/ antacids.

Adverse Effects

Side effects of Gabapentin : >10% Ataxia (1-13%),Dizziness (16-20%),Drowsiness (5-21%),Fatigue (11-15%),Somnolence (16-20%) 1-10% Diplopia (6-10%),Nystagmus (6-10%),Tremor (6-10%),Amblyopia (1-5%),Back pain (1-5%),Constipation (1-5%),Depression (1-5%),Dry mouth (1-5%),Dysarthria (1-5%),Dyspepsia (1-5%),Hostility (5-8% children),Hyperkinesia (3-5%),Increased appetite (1-5%),Leukopenia (1-5%),Myalgia (1-5%),Nervousness (1-5%),Peripheral edema (1-5%),Pharyngitis (1-5%),Pruritus (1-5%),Rhinitis (1-5%),Vasodilation (1-5%),Weight gain (1-5%),Abnormal vision (>1%),Anorexia (>1%),Arthralgia (>1%),Asthenia (>1%),HTN (>1%),Malaise (>1%),Paresthesia (>1%),Purpura (>1%),Vertigo (>1%)

Mechanism of Action

Gabapentin is structurally related to the neurotransmitter GABA but is neither a GABA agonist nor antagonist. High affinity gabapentin binding sites are located throughout the brain. These sites correspond to the presence of voltage-gated Ca channels particularly controlling the ?-2/?-1 subunit. This channel appears to be located presynaptically and may modulate the release of excitatory neurotransmitters which participate in epileptogenesis and nociception.