Gabapentin Enacarbil

Reviewed on 6/29/2022

What Is Gabapentin Enacarbil and How Does It Work?

Gabapentin Enacarbil is a prescription medication used for treating the symptoms of restless leg syndrome and postherpetic neuralgia

  • Gabapentin Enacarbil is available under the following different brand names: Horizant

What Are Side Effects Associated with Using Gabapentin Enacarbil?

Common side effects of Gabapentin Enacarbil include:

  • sleepiness
  • dizziness
  • headache

Serious side effects of Gabapentin Enacarbil include:

  • sleepiness, 
  • dizziness, 
  • slow thinking, 
  • problems with coordination
  • thoughts about suicide or dying
  • attempt to commit suicide
  • new or worse depression
  • new or worse anxiety
  • feeling agitated
  • new or worse restlessness
  • panic attacks
  • new or worse trouble sleeping (insomnia)
  • new or worse irritability
  • acting aggressive, being angry, or violent
  • acting on dangerous impulses
  • an extreme increase in activity and talking (mania)
  • other unusual changes in behavior or mood

Rare side effects of Gabapentin Enacarbil include:

  • none 

Seek medical care or call 911 at once if you have the following serious side effects:

  • Severe headache, confusion, slurred speech, arm or leg weakness, trouble walking, loss of coordination, feeling unsteady, very stiff muscles, high fever, profuse sweating, or tremors;
  • Serious eye symptoms such as sudden vision loss, blurred vision, tunnel vision, eye pain or swelling, or seeing halos around lights;
  • Serious heart symptoms such as fast, irregular, or pounding heartbeats; fluttering in your chest; shortness of breath; sudden dizziness, lightheartedness, or passing out.

This is not a complete list of side effects and other serious side effects or health problems that may occur as a result of the use of this drug. Call your doctor for medical advice about serious side effects or adverse reactions. You may report side effects or health problems to FDA at 1-800-FDA-1088


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What Are Dosages of Gabapentin Enacarbil?

Adult dosage

Tablet, extended-release

  • 300 mg
  • 600 mg

Restless Legs Syndrome (RLS)

Adult dosage

  • 600 mg every day with food at about 5:00 pm

Postherpetic Neuralgia

Adult dosage

  • 600 mg orally every morning for 3 days, and then increase to 600 mg orally twice daily

Dosage Considerations – Should be Given as Follows: 

  • See “Dosages”.

What Other Drugs Interact with Gabapentin Enacarbil?

If your medical doctor is using this medicine to treat your pain, your doctor or pharmacist may already be aware of any possible drug interactions and may be monitoring you for them. Do not start, stop, or change the dosage of any medicine before checking with your doctor, health care provider, or pharmacist first.

  • Gabapentin Enacarbil has severe interactions with no other drugs.
  • Gabapentin Enacarbil has serious interactions with the following drugs:
  • Gabapentin Enacarbil has moderate interactions with at least 127 other drugs.
  • Gabapentin Enacarbil has minor interactions with at least 17 other drugs.

This information does not contain all possible interactions or adverse effects. Visit the RxList Drug Interaction Checker for any drug interactions. Therefore, before using this product, tell your doctor or pharmacist about all your products. Keep a list of all your medications with you and share this information with your doctor and pharmacist. Check with your health care professional or doctor for additional medical advice, or if you have health questions or concerns.

What Are Warnings and Precautions for Gabapentin Enacarbil?


  • None

Effects of drug abuse

  • None

Short-Term Effects

  • See “What Are Side Effects Associated with Using Gabapentin Enacarbil?”

Long-Term Effects

  • See “What Are Side Effects Associated with Using Gabapentin Enacarbil?”


  • Safety and effectiveness in patients with epilepsy not studied
  • Somnolence and driving impairment
  • The therapy causes somnolence/sedation, dizziness, and driving impairment; patients should be advised not to drive, perform hazardous tasks, or operate complex machinery until they have gained sufficient experience to assess whether therapy impairs their ability to perform these tasks; the duration of driving impairment after starting the therapy is unknown
  • However, prescribers and patients should be aware that patients’ ability to assess their own driving competence, as well as their ability to assess the degree of somnolence caused by treatment, can be imperfect; whether the impairment is related to somnolence or other effects is unknown
  • Multiorgan hypersensitivity and drug reaction
    • Drug Reaction with Eosinophilia and Systemic Symptoms (DRESS), also known as multiorgan hypersensitivity, reported; some of these events have been fatal or life-threatening
    • Typically presents with fever, rash, and/or lymphadenopathy in association with other organ system involvement (e.g., hepatitis, nephritis, hematological abnormalities, myocarditis, myositis) and may resemble an acute viral infection
    • Eosinophilia is often present; because this disorder is variable in its expression, other organ systems not noted here may be involved; early manifestations of hypersensitivity, such as fever or lymphadenopathy, may be present even though rash is not evident
    • If such signs or symptoms are present, the patient should be evaluated immediately; therapy should be discontinued if an alternative etiology for signs or symptoms cannot be established
  • Respiratory depression
    • Serious, life-threatening, or fatal respiratory depression is reported when coadministered with central nervous system depressants, including opioids, or in the setting of underlying respiratory impairment
    • Consider initiating therapy at a low dose and monitor for symptoms of respiratory depression and sedation if co-prescribing of another CNS depressant, like an opioid, or prescribing to patients with underlying respiratory impairment
    • Management of respiratory depression may include close observation, supportive measures, and reduction or withdrawal of CNS depressants
  • Suicidal behavior and ideation
    • Gabapentin Enacarbil is a prodrug of gabapentin, an antiepileptic drug (AED); AEDs increase the risk of suicidal thoughts or behavior in patients taking these drugs for any indication; because gabapentin Enacarbil is a prodrug of gabapentin, it also increases this risk
    • Patients treated with any AED for any indication should be monitored for the emergence or worsening of depression, suicidal thoughts or behavior, and/or any unusual changes in mood or behavior
    • Anyone considering prescribing therapy must balance the risk of suicidal thoughts or behavior with the risk of untreated illness;
    • Epilepsy and many other illnesses for which AEDs are prescribed are themselves associated with morbidity and mortality and an increased risk of suicidal thoughts and behavior; should suicidal thoughts and behavior emerge during treatment, the prescriber needs to consider whether the emergence of these symptoms in any given patient may be related to the illness being treated
    • Patients, their caregivers, and families should be informed that therapy increases the risk of suicidal thoughts and behavior and should be advised of the need to be alert for the emergence or worsening of signs and symptoms of depression, any unusual changes in mood or behavior, or the emergence of suicidal thoughts, behavior, or thoughts about self-harm; behaviors of concern should be reported immediately to healthcare providers

Pregnancy and Lactation

  • Use with caution if benefits outweigh risks during pregnancy
  • Limited available data in pregnancy; use caution
  • Lactation
    • Unknown whether distributed in breast milk


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