Gabapentin

General

• Type: Anticonvulsants; GABA analog
• Dosage Forms: capsule, tablet, oral solution 250mg/5mL
• Common Trade Names: Neurontin, Gralise

Adult Dosing

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
  

Post herpetic neuralgia

• Day 1: 300 mg PO qDay
• Day 2: 300 mg PO q12hr
• Day 3: 300 mg PO q8hr
  

Muscle Cramps (Off-label)

• 100-300 mg PO qHS; may titrate to 300-400 mg q8hr PRN

Anxiety (Off-label)

• 300mg PO qHS initially, THEN 300 mg PO q8h; may further increase as tolerated
  

Diabetic Neuropthy (Off-label)

• 900 mg/day PO initially; may increase gradually q3Days to 1800-3600 mg/day

Neuropathic Pain

• 600 mg PO load in ED
• D/c with 300 mg --> 900 mg per day divided tid (as in post-herpetic neuralgia regimen)
• D/c with pain specialist follow-up
• Max dosage 3600 mg if pt already on gabapentin
• Taper dose > 7 days to discontinue

Pediatric Dosing

Partial seizures

Adjunct for partial seizures w/o secondary generalization in pts> 12yo w/ epilepsy; also adjunctive therapy for partial seizures in pts 3-12 years

• <3 years: Safety and efficacy not established
• 3-12 years (initial dose): 10-15mg/kg/day PO divided q8hr initially; titrate up in 3d to effective maintenance dose
• 3-4 years (maintenance): 40 mg/kg/day PO divided q8hr
• 5-12 years (maintenance): 25-35 mg/kg/day PO divided q8hr
• >12 years (initial dose): 300mg PO q8h; may increase up to 600 mg PO q8h

Special Populations

• Pregnancy Rating: C
• Lactation: Enters breast milk; use with caution
• Renal Dosing

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

HD: 125-350 mg posthemodialysis after each 4h dialysis interval

• Hepatic Dosing
  • Adult: no modifications
  • Pediatric: no modifications

Contraindications

• Allergy to class/drug

Adverse Reactions

Serious

• none

Common

• >10% ataxia, dizziness, fatigue, somnolence
• 1-10% diplopia, nystagmus, tremor, amblyopia, back pain, constipation, depression, dry mouth, dysarthria, dyspepsia, increased appetitie, leukopenia, myalgia, nervousness, peripheral edema, pharyngitis, puritis, rhinitis, vasodilation, weight gain

Pharmacology

• Half-life: 5-7hr
• Metabolism: not metabolized
• Excretion: Renal
• Mechanism of Action: GABA analogue, but has no effect on GABA binding, uptake or degradation; mech for analgesic and anticonvulsant activity unknown