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1.1. Adults

Gabapentin (Neurontin, Gralise) is FDA-approved for use in adults with postherpetic neuralgia (PHN). Neurontin is also approved as adjunctive therapy for managing partial seizures with or without secondary generalization in patients with epilepsy1-4. Gabapentin enacarbil (Horizant) is FDA-approved for the management of PHN and is also approved for the management of moderate-to-severe restless legs syndrme (RLS) in adults1,2,5. Neurontin, Gralise, and Horizant and equivalent generic products are not interchangeable due to differing chemical forms and pharmacokinetic properties1-5. Maximum recommended adult dosages are summarized in Table 1. The maximum time interval between Neurontin and generic gabapentin immediate-release dosing should not exceed 12 hours. Patient profiles containing doses that exceed the maximum recommended dose will be reviewed.

Table 1: Maximum Recommended Adult Gabapentin Dosages1-5
Drug NameDosage Form/StrengthTreatment IndicationMaximum Recommended Dosage
gabapentin (Neurontin, generics)100 mg, 300 mg, 400 mg immediate-release (IR) capsules 600 mg, 800 mg IR tablet 250 mg/5 mL, 300 mg/ 6 mL oral solutionPartial seizures with/without secondary generalized tonic-clonic seizures2400 mg daily in three divided doses*  
gabapentin (Neurontin, generics)100 mg, 300 mg, 400 mg IR capsules 600 mg, 800 mg IR tablet 250 mg/5 mL, 300 mg/ 6 mL oral solutionPostherpetic neuralgia-associated neuropathic pain3600 mg daily in three divided doses+  
gabapentin (Gralise)300 mg, 450 mg, 600 mg, 750 mg, 900 mg extended-release (ER) tablets  Postherpetic neuralgia-associated neuropathic pain1800 mg once daily
gabapentin enacarbil (Horizant)300 mg, 600 mg ER tabletPostherpetic neuralgia-associated neuropathic pain1200 mg daily in two divided doses
gabapentin enacarbil (Horizant)300 mg, 600 mg ER tabletRestless legs syndrome600 mg daily at 5 pm^

Legend:

  • *Doses of 3600 mg/day have also been well tolerated in small numbers of patients for abbreviated treatment durations.
  • +Doses up to 3600 mg/day have been administered with therapeutic effect; however, additional benefit with doses greater than 1800 mg/day may not be observed.
  • ^Gabapentin enacarbil doses up to 1200 mg daily have been used in clinical trials with no additional benefit and increased adverse reactions.

While not FDA-approved, gabapentin has also been evaluated in adult clinical trials for use in neuropathic pain, fibromyalgia, and vasomotor symptoms with favorable results1,2.