Brand Name : GABAMAX
Generic Name : Gabapentin
Preparations : 100 mg / 300 mg Capsules
Pharmacological Categories : Drug for neuropathic pain / Anticonvulsant

Mechanism of Action (MOA)
GABAMAX (Gabapentin) binds with α2δ-1 subunit of voltage gated calcium channels at the axon terminal of presynaptic neuron centrally and peripherally. This leads to decreased release of neurotransmitters such as glutamate, Calcitonin Gene Related Peptide (CGRP) and substance P that are involved in seizure and neuropathic pain progression.

 

Pharmacokinetics

  • Absorption : Absorbed from the gastrointestinal tract
  • Peak Plasma Concentration : 2 to 3 hours
  • Protein Binding : Minimal
  • Distribution : Widely distributed throughout the body; into breast milk
  • Metabolism : Not appreciably metabolized
  • Elimination Half-life : 5 to 7 hours
  • Excretion : Excreted through urine as unchanged drug

Indications and Dosage
Adult

  • Postherpetic Neuralgia
    Initial : One capsule of GABAMAX 300 mg on day 1, then one capsule of GABAMAX 300 mg twice daily on Day 2, and one capsule of GABAMAX 300 mg three times a day on Day 3
    Titrate : May subsequently increase up to GABAMAX 600 mg three times a day (1800 mg per day) if necessary
  • Adjuvant Therapy for Partial Onset Seizures with Epilepsy, with or without Secondary Generalization
    Initial : One capsule of GABAMAX 300 mg three times a day
    Maintenance : One to two capsules of GABAMAX 300 mg three times a day
    Doses up to GABAMAX 2400 mg per day (long-term) and GABAMAX 3600 mg per day (short-term) have been well tolerated.
    Dosing intervals should not exceed 12 hours.

Children

  • Adjuvant Therapy for Partial Onset Seizures with Epilepsy, with and without Secondary Generalization :
  • 3 to 11 years
    Initial : GABAMAX 10 to 15 mg per kg per day in 3 divided doses
    Titrate : Increase to recommended maintenance dose over a period of approximately 3 days
  • 3 to 4 years
    Maintenance : GABAMAX 40 mg per kg per day in 3 divided doses
  • 5 to 11 years
    Maintenance : GABAMAX 25 to 35 mg per kg per day in 3 divided doses
    Doses up to GABAMAX 50 mg per kg per day have been well tolerated. Dosing intervals should not exceed 12 hours.
  • 12 years of age or above
    Initial : One capsule of GABAMAX 300 mg three times a day
    Maintenance : One to two capsules of GABAMAX 300 mg three times a day
    Doses up to GABAMAX 2400 mg per day (long-term) and GABAMAX 3600 mg per day (short-term) have been well tolerated. Dosing intervals should not exceed 12 hours.
  • Renal Impairment
    12 years of age or above
    Creatinine Clearance (CrCl) more than or equal to 60 mL per min : GABAMAX 900 to 3600 mg in 3 divided doses
    CrCl 30 to 59 mL per min : GABAMAX 400 to 1400 mg per day in 2 divided doses
    CrCl 15 to 29 mL per min : GABAMAX 200 to 700 mg in single daily dose
    CrCl 15 mL per min : One capsule of GABAMAX 100 to 300 mg single daily dose
    CrCl less than 15 mL per min : Reduce daily dose in proportion to CrCl
    Hemodialysis : Dose adjustment is necessary
  • Discontinuation
    Dose Reduction / Substitution / Discontinuation : Should be done gradually over a minimum of 1 week

ADMINISTRATION : Oral route. Take with or without food. Swallow capsule whole with water.

Side Effects
MOST COMMON : Somnolence, dizziness, ataxia, fatigue
COMMON : Confusion, depression, nervousness
LESS FREQUENT : Nystagmus, tremor, diplopia, amblyopia, pharyngitis, rhinitis, dysarthria, nausea and vomiting, weight gain, oedema, dyspepsia, amnesia, weakness, paraesthesia, arthralgia, purpura, leucopenia, anxiety, urinary-tract infection
RARE : Pancreatitis, altered liver function tests, erythema multiforme, Stevens-Johnson syndrome, myalgia, headache, blood glucose fluctuations in diabetic, hallucinations and psychoses
OTHER : Acute renal failure, allergic reactions, movement disorders such as choreoathetosis, dyskinesia and dystonia, palpitations, thrombocytopenia, and tinnitus

Contraindication
Hypersensitivity

Warnings / Precautions

  • In renal impairment and those undergoing haemodialysis, false positive readings have been reported with some urinary protein tests in patients taking gabapentin.
  • Do not discontinue abruptly (may increase seizure frequency); gradually taper over a minimum of 1 week

Drug Interactions

  • Antacids containing aluminium hydroxide, aluminium with magnesium decreases absorption of gabapentin.
  • Morphine reduces the clearance of gabapentin (patients receiving both drugs should be monitored for signs of CNS depression and doses should be reduced accordingly.
  • Increased plasma concentrations with symptoms of toxicity of phenytoin, carbamazepine, and clobazam have been reported in a patient after gabapentin was added to the treatment.

Pregnancy Category : C

Presentations
GABAMAX 100 mg: A box of 10 blisters, each blister of 10 capsules
GABAMAX 300 mg: A box of 10 blisters, each blister of 10 capsules