Gabapentin, (Neurontin)®

Brand name

  • Neurontin®

Drug Class

  • Anticonvulsant
  • GABA Agonist

Preparations

  • Capsule: 100 mg, 300 mg, 400 mg

  • Solution: 250 mg/5 mL (470 mL)

  • Tablet: 600 mg, 800 mg

Indications

  • Anticonvulsant
  • Chronic pain
  • Diabetic neuropathy
  • Postoperative pain
  • Postherpetic neuralgia
  • Restless legs syndrome (RLS)
  • Hot flashes associated with menopause
  • Anxiety 
  • Prevention of alcohol withdrawal
  • Reducing craving for alcohol after being detoxed

Metabolism

  • Half-life elimination: 5-7 hours
  • Excretion: Proportional to renal function; urine (as unchanged drug)

Dosing

  • Start at 300 mg daily dose and increase slowly
  • Maximum daily dose: 3600 mg divided TID
  • For prevention of alcohol withdrawal can be started at high doses (1200 mg daily) and tapered of in 1 to 2 weeks
  • Start first dose in the weekend and with a night dose to reduce daytime somnolence
  • Dose adjustment is needed in renal impairment

Drug Interactions

Drugs that may decrease serum concentration of gabapentin or may diminish its therapeutic effects:

  • Antacid
  • Mefloquine

 

Drugs may increase the CNS depression effect of gabapentin:

  • Alcohol

Adverse Effects

Central nervous system:

  • Dizziness (17% to 28%)
  • Somnolence (20%)
  • Ataxia (13%)
  • Fatigue (11%)

Cardiovascular:

  • Peripheral edema (2% to 8%)
  • Vasodilatation (1%)

Central nervous system:

  • Fever (children 10%)
  • Hostility (children 8%)
  • Emotional lability (children 4%)
  • Fatigue (children 3%)
  • Headache (3%)
  • Ataxia (3%)
  • Abnormal thinking (2% to 3%)
  • Amnesia (2%)
  • Depression (2%)
  • Dysarthria (2%)
  • Nervousness (2%)
  • Abnormal coordination (1% to 2%)
  • Twitching (1%)
  • Hyperesthesia (1%)

Dermatologic:

  • Pruritus (1%)
  • Rash (1%)

Endocrine & metabolic:

  • Hyperglycemia (1%)

Gastrointestinal:

  • Diarrhea (6%)
  • Nausea/vomiting (3% to 4%)
  • Abdominal pain (3%)
  • Xerostomia (2% to 5%)
  • Constipation (2% to 4%)
  • Weight gain (2% to 3%)
  • Dyspepsia (2%)
  • Flatulence (2%)
  • Dry throat (2%)
  • Dental abnormalities (2%)
  • Appetite stimulation (1%)

Genitourinary:

  • Impotence (2%)

Hematologic:

  • Leukopenia (1%)
  • WBC decreased (1%)

Neuromuscular & skeletal:

  • Tremor (7%)
  • Weakness (6%)
  • Hyperkinesia (children 3%)
  • Abnormal gait (2%)
  • Back pain (2%)
  • Myalgia (2%)

Ocular:

  • Nystagmus (8%)
  • Diplopia (1% to 6%),
  • Blurred vision (3% to 4%)
  • Conjunctivitis (1%)

Respiratory:

  • Rhinitis (4%)
  • Bronchitis (children 3%)
  • Respiratory infection (children 3%)
  • Pharyngitis (1% to 3%)
  • Cough (2%)

 

Contraindications

  • History of hypersensitivity to gabapentin or any component of the formulation

Pregnancy and Breastfeeding

  • There are no adequate and well-controlled studies in pregnant women
  • Gabapentin is excreted in human breast milk. Use in breast-feeding women only if the benefits to the mother outweigh the potential risk to the infant.

Precautions

Gabapentin can be misused and reports of gabapentin misuse has been increased recently. Gabapentin misuse produces euphoria similar to opioids and benzodiazepines. Although the therapeutic dose of gabapentin is at 3600 mg daily, reports indicate doses up to 12000 mg daily being abused by some individuals.

patients who abuse gabapentin might report lost script, double doctor or ask for early refill or rapid dose escalation.

Warning

  • May cause CNS depression
  • May impair physical or mental abilities which could affect performing tasks which require mental alertness (eg, operating machinery or driving)
  • May increase risk of suicidal thoughts or behavior
  • Dose adjustment is required in patients with severe renal impairment.

References

  • Bril V, England J, Franklin GM, et al, “Evidence-Based Guideline: Treatment of Painful Diabetic Neuropathy: Report of the American Academy of Neurology, the American Association of Neuromuscular and Electrodiagnostic Medicine, and the American Academy of Physical Medicine and Rehabilitation,” Neurology, 2011, 76(20):1758-65.
  • Brown JT and Randall A, “Gabapentin Fails to Alter P/Q-Type Ca2+ Channel-Mediated Synaptic Transmission in the Hippocampus in vitro,” Synapse, 2005, 55(4):262-9.
  • Butt DA, Lock M, Lewis JE, et al, “Gabapentin for the Treatment of Menopausal Hot Flashes: A Randomized Controlled Trial,” Menopause, 2008, 15(2):310-8.
  • Evoy KE, Morrison MD, Saklad SR. Abuse and misuse of pregabalin and gabapentin.
    drugs. 2017 Mar;77(4):403-26.
    PubMed:
  • Shanthanna H, Gilron I, Rajarathinam M, AlAmri R, Kamath S, Thabane L, et al.
    Benefits and safety of gabapentinoids in chronic low back pain: a systematic review
    and meta-analysis of randomized controlled trials. Plos Medicine. 2017;14(8).
  • Smith RV, Havens JR, Walsh SL. Gabapentin misuse, abuse and diversion: a
    systematic review. Addiction. 2016 Jul;111(7):1160-74.

Note

This document is prepared by the “Mental Health for All” team. This document is provided for information purposes only and does not necessarily represent endorsement by or an official position of the Essentials of Medicine. Advice on the treatment or care of an individual patient should be obtained through consultation with a physician who has examined that patient or is familiar with that patient’s medical history.

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