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Overview: Horizant is used to help certain people with restless legs or nerve pain. Common side effects include dizziness, sleepiness, and headache. You should not not drive or do other activities that require alertness or coordination like operating heavy machinery until you know how Horizant affects you. Tell you health care provider about all of your health conditions and any medicines you take before you start taking Horizant. 

Uses

What is Horizant used for?

Horizant (gabapentin enacarbil) is commonly used to treat the following conditions.

Horizant may also be used for other conditions as determined by your health care provider.

How does Horizant work (mechanism of action)?

Horizant is broken down by your body to make gabapentin. The exact way that gabapentin works for RLS and postherpetic neuralgia is unknown. Gabapentin may block certain signals from nerves.

How is Horizant supplied (dosage forms)?

Brands and other names

  • Horizant

Dosage forms and strengths

  • 300 mg extended-release oral tablets
  • 600 mg extended-release oral tablets

How should I store Horizant?

Horizant should be stored at room temperature, between 68 F and 77 F (20 C and 25 C). It can be exposed to temperatures between 59 F and 86 F (15 C and 30 C), for shorter periods of time, such as when transporting it. Store in a cool, dry place. Do not remove any moisture control packs provided in the bottle.

Side Effects

What are the most common side effects of Horizant?

The most common side effects of Horizant are listed below. Tell your health care provider if you have any of these side effects that bother you.

  • Sleepiness
  • Dizziness
  • Headache

There may be other side effects of Horizant that are not listed here. Contact your health care provider if you think you are having a side effect of a medicine. In the U.S., you can report side effects to the FDA at www.fda.gov/medwatch or by calling 800-FDA-1088 (800-332-1088). In Canada, you can report side effects to Health Canada at www.health.gc.ca/medeffect or by calling 866-234-2345.

What are the serious side effects of Horizant?

While less common, the most serious side effects of Horizant are described below, along with what to do if they happen.

Sleepiness, Dizziness, and Driving Impairment. Horizant may cause dizziness and sleepiness and can affect your alertness or coordination, including the morning after you take your dose. Horizant can impair your ability to safely drive. Do not drive or do other activities that require alertness or coordination like operating heavy machinery until you know how Horizant affects you. How long Horizant may impair your ability to drive is unknown. Ask your health care provider when you can drive or do other activities.

Suicidal Thoughts and Actions. Horizant may cause suicidal thoughts or actions in a small number of people. If you are about to harm yourself, call 911 or call or text 988, the Suicide & Crisis Lifeline. Call your health care provider right away if you have any of the following symptoms.

  • New or increased thoughts of suicide or death
  • Suicide attempt
  • New or increased feelings of anxiety, depression, or other unusual changes in the mood or behavior

Severe Allergic Reactions. Horizant can cause allergic reactions, including DRESS, which can be serious. DRESS stands for Drug Reaction with Eosinophilia and Systemic Symptoms. It is also sometimes called multiorgan hypersensitivity. This is a reaction that can affect multiple parts of the body including your liver, kidneys, and heart. Stop taking Horizant and get help right away if you have any of the following symptoms of a serious allergic reaction.

  • Breathing problems or wheezing
  • Racing heart
  • Itching or skin rash
  • Bumps on the skin called hives that can be red, pink, white, or brown depending on your skin tone
  • Fever or general ill feeling
  • Swollen lymph nodes
  • Swelling of the face, lips, mouth, tongue, or throat
  • Trouble swallowing or throat tightness
  • Nausea or vomiting
  • Dizziness, feeling lightheaded, or fainting
  • Frequent infections
  • Stomach cramps
  • Joint or muscle pain
  • Unusual bruising or bleeding
  • Swelling in your feet, ankles, or legs
  • Dark-colored urine
  • Your skin or the whites of your eyes turning yellowish in color (also called jaundice)

Breathing Problems. Horizant may cause slow and shallow breathing, especially if you have breathing problems from another condition or take other medicines that can slow your breathing. See the Interactions section for more details. Tell your health care provider if you develop severe sleepiness, especially when you start Horizant or when your dose is increased. Get emergency help if you have any of the following symptoms.

  • Changes in the color of your skin, including bluish color to your lips and fingernails
  • Confusion
  • Shortness of breath
  • Feeling dizzy, lightheaded, or fainting
  • Changes in your heart rate or rhythm, such as a fast, slow, pounding or skipping heartbeat
  • Fast breathing or very slow breathing

Warnings & Precautions

Who should not use Horizant?

Allergies to Ingredients. People who are allergic to any of the following should not take Horizant.

  • Gabapentin enacarbil
  • Gabapentin
  • Horizant
  • Any of the ingredients in the specific product dispensed

Your pharmacist can tell you all the ingredients in Horizant.

What should I know about Horizant before using it?

Do not take Horizant unless it has been prescribed to you by a health care provider. Take it as prescribed. Different forms of gabapentin are not interchangeable even if the strength is the same. Always follow the instructions given by your health care provider, and take the specific medicine prescribed to you.

Do not stop taking Horizant without talking to your health care provider. Stopping Horizant suddenly can cause side effects, including seizures. If you need to stop taking Horizant, your health care provider will give you instructions on how to stop the medicine.

Do not share Horizant with other people, even if they have the same condition as you. It may harm them.

Keep Horizant out of the reach of children.

Do not chew, cut, or crush Horizant extended-release tablets. Swallow the medicine whole.

Take Horizant with food. 

Horizant is not for people with restless legs syndrome who need to sleep during the day and be awake at night.

What should I tell my health care provider before using Horizant?

Tell your health care provider about all of your health conditions and any prescription or over-the-counter (OTC) medicines, vitamins/minerals, herbal products, and other supplements you are using. This will help them know if Horizant is right for you.

In particular, make sure that you discuss any of the following.

Mental Health Problems. Tell your health care provider about any recent and current mental health problems, especially if you have had thoughts of suicide, have ever attempted suicide, or have depression or mood problems.

Substance Use Disorder. Tell your health care provider if you have a history of a drug or alcohol disorder. 

Current and Past Health Conditions. Tell your health care provider if you have any of the following.

  • Kidney problems or on dialysis
  • Breathing problems
  • Seizures

Other Medicines and Supplements. Horizant may interact with other medicines and supplements. Before taking Horizant, tell your health care provider about any prescription or over-the-counter (OTC) medicines, vitamins/minerals, herbal products, and other supplements you are using. See the Interactions section for more details.

Pregnancy. It is not known if or how Horizant could affect pregnancy or harm a fetus. Tell your health care provider if you are pregnant or plan to become pregnant. Your health care provider will let you know if you should take Horizant while you are pregnant or trying to get pregnant.

Breastfeeding. Your body turns Horizant into a medicine called gabapentin, which passes into breast milk. Tell your health care provider if you are breastfeeding or plan to breastfeed. Your health care provider will let you know if you should take Horizant while breastfeeding. 

How can I get more information about Horizant?

For more information about Horizant, you can visit the drugmaker’s website at www.HORIZANT.com or call them at 800-461-7449.

Interactions

Does Horizant interact with foods or drinks?

There are no known interactions between Horizant and foods or drinks.

Do not drink alcohol while taking Horizant. The risk of serious problems such as severe dizziness, sleepiness, and nausea may be increased because the medicine is released faster when taken with alcohol.

Does Horizant interact with other medicines (drug interactions)?

Always tell your health care provider about any prescription or over-the-counter (OTC) medicines, vitamins/minerals, herbal products, and other supplements you are using. 

In particular, make sure that you discuss if you are using any of the following before taking Horizant.

  • Any other medicine that causes dizziness and sleepiness (e.g., prescription pain medicines such as hydrocodone, morphine, or oxycodone, sleep medicines such as zolpidem, and medicines for anxiety such as lorazepam)
  • Other gabapentin medicines, such as Neurontin or Gralise

This may not be a complete list of medicines that can interact with Horizant. Always check with your health care provider.

Does interact with other drugs you are taking?

Enter your medication into the WebMD interaction checker

Overdose/Missed Dose

What should I do if I accidentally use too much Horizant?

If you or someone else has taken too much Horizant, get medical help right away, call 911, or contact a Poison Control center at 800-222-1222.

What should I do if I miss a dose of Horizant?

If you miss a dose, skip the missed dose, and only take the next dose at your scheduled time. Do not take double or extra doses.