Population pharmacokinetics and pharmacodynamics of gabapentin after administration of gabapentin enacarbil.

Gabapentin enacarbil (GEn) is an actively transported prodrug of gabapentin that provides sustained dose-proportional exposure to gabapentin and predictable bioavailability. Gabapentin enacarbil is approved by the US Food and Drug Administration for the treatment of moderate-to-severe primary restless legs syndrome (RLS) in adults. Using plasma gabapentin concentration data obtained after administration of GEn in 12 phase 1 to 3 GEn studies in healthy adults or patients with RLS (dose range, 300-2400 mg/d), a population pharmacokinetic (PK) model was developed by nonlinear mixed-effect modeling using NONMEM.

A randomized, double-blind, placebo-controlled, dose-response study to assess the pharmacokinetics, efficacy, and safety of gabapentin enacarbil in subjects with restless legs syndrome.

Objective: The objective of this study was to determine steady-state gabapentin exposures and corresponding relief of symptoms and safety profile produced by 4 dose levels of gabapentin enacarbil (GEn) in subjects with restless legs syndrome (RLS).

Methods: Subjects with RLS (n = 217) were randomized to receive once-daily, orally administered GEn 600 (n = 48), 1200 (n = 45), 1800 (n = 38), or 2400 mg (n = 45) or placebo (n = 41) in this 12-week, double-blind, multicenter study (NCT01332305). Clinic visits were at screening, baseline, and weeks 1, 2, 3, 4, 6, 8, 10, and 12; plasma gabapentin concentrations were measured by a validated liquid chromatography-mass spectrometry/mass spectrometry method at weeks 4 and 12.

A 52-week study of gabapentin enacarbil in restless legs syndrome.

Objectives: This open-label, multicenter, 52-week extension study (NCT00333359) assessed the long-term safety and efficacy of gabapentin enacarbil in subjects with moderate-to-severe primary restless legs syndrome (RLS).

Methods: Subjects had completed one of 4 randomized, double-blind parent studies (XP052/XP053/XP081/XP083). Gabapentin enacarbil 1200 mg was administered once daily at 5 pm; dose adjustments to 600 or 1800 mg were permitted based on investigator judgment.