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    Horizant

    Drug - Horizant (gabapentin enacarbil extended release) [GSK and XenoPort] 

    June 2012

    Therapeutic area - Restless Legs Syndrome (RLS) and Post-Herpetic Neuralgia (PHN)

    Approval criteria for RLS

    • Patient has a diagnosis of PRIMARY restless legs syndrome (RLS) AND
    • Patient has CrCl >30 mL/min and is not on hemodialysis AND
    • Patient is intolerant to; OR has failed an adequate trial or either pramipexole OR ropinirole AND
    • Patient has had a trial of immediate release gabapentin showing some therapeutic benefit AND has a compelling therapeutic need to administer gabapentin once daily

    Supply limit for RLS

    • Max Daily Dose Allowed = 1 capsule (34 capsules per 34-day supply)
    • Max Daily Dose Allowed for patients with CrCl 30-59 mL/min = 1 capsule every other day (16 capsules per 34-day supply)*

    Approval criteria for PHN

    • Patient must have a diagnosis of postherpetic neuralgia (PHN) AND
    • CrCl > 30 mL/min and not on hemodialysis AND
    • Patient must have an intolerance to; or have tried and failed an adequate trial of a tricyclic antidepressant AND
    • Patient has had a trial of immediate release gabapentin showing some therapeutic benefit and has a compelling therapeutic need to administer gabapentin once daily

    Supply limit for PHN

    Max Daily Dose Allowed = 2 capsules (68 capsules per 34-day supply)

    Background information

    Gabapentin enacarbil, a prodrug of the generically available antiepileptic drug gabapentin, is indicated for the treatment of moderate-to-severe primary restless legs syndrome (RLS) and postherpetic neuralgia (PHN) in adults. Gabapentin, the active ingredient in Horizant, is a known anticonvulsant and is commonly used in the treatment of various types of pain syndromes.

    Pharmacokinetics

    Immediate-release gabapentin and Horizant cannot be substituted on a milligram for milligram basis. Gabapentin encarbil has dose-proportional pharmacokinetic parameters while immediate release gabapentin does not. The clinical relevance of the dose-proportionality differences between these two products is unknown at this time. According to FDA labeling, Horizant must be taken with food while the FDA labeling for immediate release gabapentin states it can be taken with or without food.

    Pharmacokinetic Parameters in Adults

    Parameter Horizant 600 mg QD Gabapentin 300 mg TID
    Tmax (h) 7.3 NA
    T 1/2 (h) 5-6 5-7 
    Bioavailability 75% (dose proportional) 60% (non-dose proportional)

    Cost Comparison** State Reimbursement to Pharmacies per Rx
    Horizant 600 mg QD $104.63
    Gabapentin 300 mg immediate release TID $14.98

    ** Cost comparison is for information purposes only and is based on actual claims data

    *Important: 
    HORIZANT is not recommended for use in patients with a CrCl <30 mL/min or on hemodialysis because the dose cannot be reduced below 600 mg.

    Questions?

    MHCP Provider Call Center 651-431-2700 or 800-366-5411

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