Drug - Horizant (gabapentin enacarbil extended release) [GSK and XenoPort]
June 2012
Therapeutic area - Restless Legs Syndrome (RLS) and Post-Herpetic Neuralgia (PHN)
Max Daily Dose Allowed = 2 capsules (68 capsules per 34-day supply)
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.
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.
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