Gabapentin

Aka: Gabapentin, Neurontin

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II. Precautions: Risk of Abuse

  1. Gabapentin and Pregabalin (Lyrica) are abused by patients on Opiates to potentiate CNS Opiate effects
  2. More than one quarter of Opiate patients have abused Gabapentin
  3. Pregabalin (Lyrica) is more potent with faster onset and has higher abuse potential than Gabapentin
  4. Lyrica is categorized as DEA Controlled Substance Class V (and Gabapentin in several states)
  5. Smith (2012) Br J Gen Pract 62(601):406-7 +PMID:22867659 [PubMed]

III. Indications

  1. Neuropathic pain (Peripheral Nerve syndromes)
    1. Diabetic Neuropathy
    2. Postherpetic Neuralgia (FDA approved)
    3. Trigeminal Neuralgia
    4. Cancer Pain Management
  2. Multiple Sclerosis
  3. Parkinson's Disease
  4. Fibromyalgia
  5. Restless Legs Syndrome
    1. Effective in idiopathic RLS
      1. Happer (2001) Neurology 57(9):1717-9 [PubMed]
    2. Effective in RLS among Hemodialysis patients
      1. Thorp (2001) Am J Kidney Dis 38(1):104-108 [PubMed]
  6. Epilepsy
    1. Generalized Tonic Clonic Seizures (rarely used)
    2. Partial Seizures (adjunctive agent, FDA approved)
  7. Bipolar Disorder
  8. Anxiety Disorder
    1. Post-Traumatic Stress Disorder (PTSD)
    2. Social Phobia
    3. Generalized Anxiety Disorder
  9. Alcohol Dependence
    1. Doses of 600 mg orally three times daily appear to decrease Alcohol cravings
  10. Opioid Dependence

IV. Efficacy

  1. Chronic Pain (NNT 4.3)
  2. Diabetic Neuropathy (NNT 2.9)
  3. Postherpetic Neuralgia (NNT 3.9)

V. Safety

  1. Pregnancy Category C
  2. Excreted in Breast Milk
  3. Safe in liver disease (not hepatically metabolized)

VI. Mechanism

  1. GABA amino acid derivative (does not bind GABA-A or GABA-B receptors)
  2. Binds presynaptic alpha2-delta1 subunit of Central Nervous System voltage-gated Calcium channels
  3. Decreases excitatory Neurotransmitter release and activity

VII. Metabolism

  1. Bioavailability varies by dose
    1. Larger doses have lower bioavailability
    2. Divided doses result in better bioavailability
  2. Primarily renal excretion in its original form (not metabolized)
  3. Half-life: 5 to 7 hours
  4. Therapeutic Dose: 4-8 ug/ml

VIII. Adverse Effects: Standard Dosing

  1. Most common
    1. Sedation
    2. Dizziness
    3. Ataxia
  2. Other adverse effects
    1. Weight gain
    2. Nausea
    3. Fatigue
    4. Nystagmus
  3. Withdrawal symptoms
    1. Avoid stopping abruptly from higher doses (taper off)

IX. Adverse Effects: Overdose

  1. Acute Overdose: Sedative-Hypnotic effects
    1. Sleepy or lethargic
    2. Normal Vital Signs
  2. Chronic toxicity (especially with Renal Insufficiency)
    1. Progressive weakness
    2. Fatigue
    3. Altered Level of Consciousness
    4. Falls

X. Preparations: Newer related agents

  1. Pregabalin (Lyrica)
    1. Indicated in Neuropathy
    2. More potent than Gabapentin, and possibly less Fatigue

XI. Dosing: Neuropathy in Adults

  1. Starting Dose
    1. Start at 300 mg orally at bedtime
    2. Advance to 300 mg orally three times daily (over 4-7 days)
    3. Plan to ultimately increase to 600 mg three times daily
    4. Patients tolerate starting 300 three times daily without titrating
    5. Fisher (2001) Neurology 56(6):743-8 [PubMed]
  2. Average Dose: 600 mg orally three times daily
  3. Maximum Dose: 1200 mg orally three times daily
    1. No increase in bioavailability above 1200 mg orally three times daily
    2. Minimal pain benefit above 1800 mg/day in most conditions studied
  4. Stopping (similar to Pregabalin)
    1. Taper off agent over 1 week or more
    2. Avoid stopping abruptly due to withdrawal symptoms

XII. Dosing: Seizure Prophylaxis

  1. Age 3-12 years old
    1. Gabapentin 10-15 mg/kg (max 40 mg/kg) daily divided three times daily
  2. Age >12 years old
    1. Gabapentin 300-900 mg (max 1800) daily divided three times daily

XIII. Dosing: Miscellaneous

  1. Postherpetic Neuralgia
    1. Day 1: 300 mg orally once
    2. Day 2: 300 mg orally twice daily
    3. Day 3: 300 mg orally three times daily
    4. Titrate as needed for reduction in pain (up to 1800 mg/day)
  2. Restless Leg Syndrome
    1. Start 300 mg orally 2 hours before bed
  3. Alcohol Dependence
    1. Target dose 600 mg orally three times daily (start lower and titrate to dose)

XIV. Drug Interactions

  1. No significant Drug Interactions
  2. However, Renal Insufficiency results in drug accumulation

XV. Disadvantages

  1. Low potency as antiepileptic

XVI. References

  1. (2016) Crit Dec Emerg Med 30(9):24
  2. LoVecchio (2022) Crit Dec Emerg Med 36(4): 36
  3. Lapoint (2021) EM:Rap 21(6): 16-7
  4. Wiffen (2005) Cochrane Database Syst Rev (3):CD005452 +PMID: 16034978 [PubMed]

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Related Studies

Cost: Medications

gabapentin (on 5/17/2017 at Medicaid.Gov Survey of pharmacy drug pricing)
GABAPENTIN 100 MG CAPSULE Generic $0.03 each
GABAPENTIN 250 MG/5 ML SOLN Generic $0.12 per ml
GABAPENTIN 300 MG CAPSULE Generic $0.04 each
GABAPENTIN 400 MG CAPSULE Generic $0.07 each
GABAPENTIN 600 MG TABLET Generic $0.10 each
GABAPENTIN 800 MG TABLET Generic $0.14 each
neurontin (on 6/1/2017 at Medicaid.Gov Survey of pharmacy drug pricing)
NEURONTIN 100 MG CAPSULE Generic $0.03 each
NEURONTIN 250 MG/5 ML SOLN Generic $0.12 per ml
NEURONTIN 300 MG CAPSULE Generic $0.04 each
NEURONTIN 400 MG CAPSULE Generic $0.07 each
NEURONTIN 600 MG TABLET Generic $0.10 each
NEURONTIN 800 MG TABLET Generic $0.14 each
FPNotebook does not benefit financially from showing this medication data or their pharmacy links. This information is provided only to help medical providers and their patients see relative costs. Insurance plans negotiate lower medication prices with suppliers. Prices shown here are out of pocket, non-negotiated rates. See Needy Meds for financial assistance information.

Ontology: gabapentin (C0060926)

Definition (NCI_NCI-GLOSS) A substance that is being studied as a treatment for relieving hot flashes in women with breast cancer. It belongs to the family of drugs called anticonvulsants.
Definition (NCI) A synthetic analogue of the neurotransmitter gamma-aminobutyric acid with anticonvulsant activity. Although its exact mechanism of action is unknown, gabapentin appears to inhibit excitatory neuron activity. This agent also exhibits analgesic properties. (NCI04)
Definition (CSP) cyclohexananeacetic acid originally used as an anticonvulsant, found to have diverse CNS depressant actions.
Definition (PDQ) A synthetic analogue of the neurotransmitter gamma-aminobutyric acid with anticonvulsant activity. Although its exact mechanism of action is unknown, gabapentin appears to inhibit excitatory neuron activity. This agent also exhibits analgesic properties. Check for "http://www.cancer.gov/Search/ClinicalTrialsLink.aspx?id=38402&idtype=1" active clinical trials or "http://www.cancer.gov/Search/ClinicalTrialsLink.aspx?id=38402&idtype=1&closed=1" closed clinical trials using this agent. ("http://nciterms.nci.nih.gov:80/NCIBrowser/ConceptReport.jsp?dictionary=NCI_Thesaurus&code=C1108" NCI Thesaurus)
Concepts Pharmacologic Substance (T121) , Organic Chemical (T109)
MSH C040029
SnomedCT 108402001, 386845007
LNC LP17989-2, MTHU012288
English 1-(aminomethyl)cyclohexaneacetic acid, 1-(aminomethyl)cyclohexaneacetic Acid, gabapentin (medication), GABAPENTIN, gabapentin [Chemical/Ingredient], Convalis, gabapentin, Gabapentin, Gabapentin (product), Gabapentin (substance)
Spanish gabapentina (producto), gabapentina (sustancia), gabapentina
Derived from the NIH UMLS (Unified Medical Language System)

Ontology: Neurontin (C0678176)

Definition (CHV) a kind of pain relieving drug
Concepts Pharmacologic Substance (T121) , Organic Chemical (T109)
MSH C040029
English Neurontin, neurontin, Aventis brand of gabapentin, Parke Davis brand of gabapentin, Pfizer brand of gabapentin, Warner-Lambert brand of gabapentin
Derived from the NIH UMLS (Unified Medical Language System)

Related Topics in Pharmacology

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