gabapentin enacarbil

Adjunctive therapy

Brands: Horizant

Last reviewed 2025-12-30

Reviewed by PsychMed Editorial Team.

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Quick answers

What is gabapentin enacarbil?
Gabapentin enacarbil (brand Horizant) is an extended-release prodrug of gabapentin indicated for moderate-to-severe primary RLS and for postherpetic neuralgia (label).
What is Horizant?
Horizant is a brand name for gabapentin enacarbil.
What is Horizant (gabapentin enacarbil) used for?
Label indications include: Treatment of moderate-to-severe primary restless legs syndrome; postherpetic neuralgia (label).
What drug class is Horizant (gabapentin enacarbil)?
Prodrug of gabapentin (alpha-2-delta ligand) used for moderate-to-severe primary restless legs syndrome and postherpetic neuralgia; converted by esterases to gabapentin (not CYP-mediated) with renal elimination of released gabapentin.
What strengths does Horizant (gabapentin enacarbil) come in?
Extended-release tablets: 300 mg and 600 mg (label).

Snapshot

Class: Adjunctive therapy
Common US brands: Horizant
Therapeutic drug monitoring not routinely recommended.
Last reviewed: 2025-12-30

Label indications

Treatment of moderate-to-severe primary restless legs syndrome; postherpetic neuralgia (label).

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Clinical Highlights

Gabapentin enacarbil (brand Horizant) is an extended-release prodrug of gabapentin indicated for moderate-to-severe primary RLS and for postherpetic neuralgia (label). It is an alpha-2-delta ligand (via conversion to gabapentin). Compared with dopamine agonist options for RLS, alpha-2-delta ligands are often considered when painful sensations and insomnia are prominent or when long-term dopaminergic risks (notably augmentation) are a concern (guideline/clinical).

The main tolerability issues are somnolence and dizziness; monitoring focuses on next-day function, falls risk, and additive sedation with alcohol or other CNS depressants (label/clinical).
Because released gabapentin is cleared renally, dose selection is tied to kidney function and requires adjustment in renal impairment (label).
The compare view, gabapentin enacarbil evidence feed, and print page support side-by-side review of RLS options and practical monitoring topics.

Dosing & Formulations

Extended-release tablets: 300 mg and 600 mg (label). RLS: 600 mg once daily taken at about 5 PM with food; if a dose is missed, the next dose is taken the following day at the usual time (label).

Postherpetic neuralgia: 600 mg in the morning for 3 days, then 600 mg twice daily with food (label).
Tablets are taken whole; crushing or chewing can alter the extended-release profile and increase adverse effects (label).

Monitoring & Risks

Somnolence and dizziness can occur; next-day impairment and falls risk are key follow-up topics, especially in older adults and in polypharmacy (label/clinical). Additive CNS depression can occur with alcohol, opioids, benzodiazepines, sedating antihistamines, and other hypnotics; risk assessment focuses on total sedative burden (label/clinical).

Class warning: antiepileptic drugs have been associated with suicidal thoughts/behaviors; mood and safety monitoring is appropriate when risk is elevated (label/class).
Peripheral edema and weight gain can occur; baseline and follow-up weights and edema screening are common in longer courses (label/clinical).

Drug Interactions

Gabapentin enacarbil and released gabapentin are not CYP substrates, inhibitors, or inducers; interaction management is mainly about additive sedation and renal clearance rather than CYP-mediated effects (label). CNS depressants (including alcohol) increase impairment risk; careful review of combined sedatives and substance use is part of safety planning (label/clinical).

Changes in kidney function can change exposure and tolerability, so reassessment is common when renal status changes (clinical).

Practice Notes

For RLS, contributors such as iron deficiency, untreated sleep apnea, and medication triggers are often addressed in parallel with medication selection (guideline/clinical). When a dopamine agonist is being considered, discussion often includes the potential for long-term symptom worsening (augmentation) and impulse-control symptoms; gabapentin enacarbil is an alternative class option (guideline/clinical).

When daytime sedation limits adherence, dose timing (about 5 PM for RLS) and reduction of other sedatives are common adjustment levers before concluding the medication is not tolerable (clinical).

References

Horizant (gabapentin Enacarbil) Extended Release Tablets Prescribing Information — DailyMed (2025)
Treatment of restless legs syndrome and periodic limb movement disorder: an American Academy of Sleep Medicine clinical practice guideline — Journal of Clinical Sleep Medicine (2025)
The Management of Restless Legs Syndrome: An Updated Algorithm — Mayo Clinic Proceedings (2021)
Gabapentin Enacarbil IN Japanese Patients With Restless Legs Syndrome: A 12 Week, Randomized, Double Blind, Placebo Controlled, Parallel Group Study — Current Medical Research and Opinion (2012)