Gabapentin Enacarbil (Oral)

Gabapentin enacarbil is used in the treatment of patients who are suffering from a neurological condition called Restless Legs Syndrome.


In the US, gabapentin enacarbil is also known as 'Horizant'. It is a prescription only drug that comes in extended-release tablet form.

The medication is the preferred treatment for the moderate to severe form of a neurological disorder that is known as primary Restless Legs Syndrome (RLS)'. This condition causes feelings of discomfort or pain in the patient's legs, causing an irresistible urge to move the legs in an effort to relieve the discomfort. The medicine can also be used in adult patients to treat certain symptoms caused by a painful illness that sometimes occurs as a complication of shingles.

The medication belongs to a family of drugs known as anticonvulsant or anti-seizure medicines. Although it is very effective in controlling the symptoms that these illnesses can cause, gabapentin enacarbil will not cure them.

Conditions treated

Type of medicine

  • Anticonvulsant
  • Extended-release tablet

Side effects

As well as the effects it is intended to have, a drug may also cause a few unwanted side effects. Not every patient will experience any or all of these effects, but if they do affect you, you should seek further medical attention.

You should speak with your doctor right away if you notice any of the effects that are mentioned in the list below:

  • Jaundice
  • Pain in the stomach or upper right abdomen
  • Unusual bruising or bleeding
  • Problems with concentrating
  • Tiredness
  • Tingling of the feet or hands
  • Suicidal thoughts
  • Painful, swollen, or tender lymph glands in the groin, neck, or armpit
  • Swelling of the feet, face, or lower legs
  • Sores, white spots, or ulcers, or white spots inside the mouth or on the lips
  • Sore throat
  • Rash
  • Rapid, shallow breathing
  • Unexplained rapid weight gain
  • Difficult or painful urination
  • Nausea or vomiting
  • Loss of interest or pleasure
  • Poor appetite
  • Irritability
  • Feeling empty or sad
  • Rapid heartbeat
  • Fainting
  • Lightheadedness or dizziness
  • Discouragement
  • Breathing difficulties
  • Confusion
  • Chills or fever
  • Discomfort or chest pains
  • Behavioral changes
  • Bloody or cloudy urine
  • Swelling or bloating of the arms, face, hands, feet, or lower legs
  • Black, tarry stools

There are a number of side effects that may be caused by gabapentin enacarbil that do not usually need further medical treatment. These effects often go away as your body gets used to the new medicine. Your doctor may be able to offer some advice on ways in which you can manage or prevent some of these effects. If you notice any of the following temporary side effects that refuse to go away or are especially troublesome, check with your GP:

  • Weight gain
  • Sleepiness or unusual drowsiness
  • Sensation of spinning
  • Lack or loss of strength
  • Inability to have or keep an erection
  • Excess air or gas in the stomach or intestines
  • Dry mouth
  • Decreased interest in sexual intercourse
  • Blurred vision

Not every side effect that has been reported by patients using this medicine is listed in this guide. If you find that you are experiencing effects that are not referred to here, you should consult your medical practitioner right away for advice.


You should take gabapentin enacarbil precisely as you have been instructed to by your treating physician. You must not take less or more of the drug, do not take it more often, or take it for a longer period than prescribed. If you do, you may increase the risk of side effects.

Your prescription will be given to you with a patient medication guide. Be sure to read all the information that is contained in the guide, and ask your GP if you do not understand anything that it contains.

It is recommended that you swallow each of the gabapentin enacarbil tablets in one piece. Do not chew, break, or crush them. You should take your tablets with a meal to avoid unwanted side effects.

If you are taking gabapentin enacarbil to treat Restless Legs Syndrome, you must not use this medicine if you need to sleep by day and remain awake during the night.

You should only use the exact brand of gabapentin enacarbil that you were prescribed by your doctor, as different brands may not work in the same way.

It is important for patients to note that the dose of this medicine is not the same for everyone. You should follow your doctor's instructions or the directions contained on the dispensary label. If your dose is not the same as this, do not change it unless you are told to do so by your treating physician.

The size of your dose of gabapentin enacarbil will depend on the strength of the preparation. In addition, the number of daily doses you take, the time you should leave between them, and the total duration of your course of treatment will depend on the medical condition for which you are being treated.

Extended-release tablets for the treatment of Restless Legs Syndrome:

  • Adults: Take 600 mg daily in one dose at around 17:00 hrs.
  • Children: The dose and use of this drug will be as instructed by your GP.

Extended-release tablets for the treatment of postherpetic neuralgia:

  • Adults: Initially, take 600 mg daily in one dose each morning for three days. Your GP will then increase the dose. You may take up to 600 mg twice daily.
  • Children: The dose and use of this drug will be as instructed by your GP.

If you omit to take a dose of your gabapentin enacarbil, miss out the one you omitted and revert to your prescribed schedule of dosing. Never take twice the dose.

Do not share your prescription of gabapentin enacarbil with anyone else.

If you think that the medication is making your condition worse, or if you think that you are not getting any better, check with your treating physician.

Drug interactions

There are some medicines that must never be used at the same time under any circumstances, as to do so could cause a serious interaction. In other cases, it may be possible to use two drugs together, even if they do interact. In this case, your GP may change the dose or advise you on other precautions that you should take. When you are using gabapentin enacarbil, it is essential that you tell your doctor if you are taking any of the following drugs.

It is not generally recommended to use this medication with any of the following drugs, although it may be necessary in some cases. If you are prescribed both medicines at the same time, your GP may alter the dose or frequency of use of the drugs:

  • Orlistat
  • Morphine
  • Magnesium Trisilicate
  • Magnesium Oxide
  • Magnesium Hydroxide
  • Magnesium Carbonate
  • Magaldrate
  • Ginkgo
  • Dihydroxyaluminum Sodium Carbonate
  • Dihydroxyaluminum Aminoacetate
  • Aluminum Phosphate
  • Aluminum Hydroxide
  • Aluminum Carbonate, Basic

Other interactions

Some medicines should not be taken when you are eating or when you are eating particular food groups, as this could cause an interaction. In addition, using alcohol or tobacco with certain drugs can also cause interactions. You should discuss this aspect of your treatment with your GP before you start taking gabapentin enacarbil.

Medical interactions

Some historical or existing medical conditions can affect the use of gabapentin enacarbil. You must tell your GP if you have any of the following conditions.

Gabapentin enacarbil should not be used by patients who have a history of depression or mental illness, as it can make these conditions worse.

Caution should be exercised when prescribing gabapentin enacarbil to patients with a history of kidney problems. The effects of the drug can be exacerbated due to the slower removal of substances from the body. This could therefore lead to overdose if the dose rate is not adjusted accordingly.


When you decide to use a particular medicine, you should weigh the benefits of using it against the risks it may present. You will arrive at this decision following discussions with your GP or treating specialist.

During the course of your treatment with gabapentin enacarbil, you must attend your doctor for regular check-up appointments. These appointments are important as they allow your GP to check that the medicine is working as intended and that no side effects are bothering you.

Before you begin using gabapentin enacarbil, you must tell your GP if you have any known allergies to this or to any other prescription or non-prescription drug. You should also mention any bad reactions that you have had to food colors, preservatives, animal by-products or certain food types.


Although it has not been noted that this drug causes any geriatric-specific issues, older patients are more likely to suffer from age-related kidney problems. Caution should therefore be exercised when calculating the dose of gabapentin enacarbil for geriatric patients.

Pregnancy and breastfeeding

There is no evidence to suggest that gabapentin enacarbil causes harm to the fetus. However, if you are expecting a baby, you should tell your GP before you start using the drug.

It is not clear whether gabapentin enacarbil passes into breast milk. However, you should consider the risks and benefits of using this medicine while you are breastfeeding.

Medical complications

Gabapentin enacarbil can cause drowsiness and dizziness in some patients. If you are affected in this way, do not drive or use machinery. Avoid any activity that could be dangerous if you are not fully alert.

This drug can cause feelings that may be out of character for some patients. If you notice that you are experiencing any of the following feelings, check with your doctor right away:

  • Feeling irritable, nervous, hostile, or restless
  • Feeling hopeless or sad
  • Experiencing suicidal thoughts or tendencies
  • Becoming easily upset

If you notice any of the following symptoms, you may be experiencing a serious allergic reaction to gabapentin enacarbil. In this case, you must seek emergency medical help right away:

  • Fever
  • Rash
  • Tender, painful or swollen lymph glands in the armpit, neck, or groin
  • Unusual bruising or bleeding
  • Yellowing of the skin or eyes

You must not stop using gabapentin enacarbil unless you are told to by your GP. If you stop using the drug abruptly, you may experience seizures. Your GP will probably advise you to gradually lower your dose until you can stop taking it altogether.

You should not drink alcohol while you are taking gabapentin enacarbil.

Do not start taking any other medications, including over the counter products, vitamins, herbal remedies, and diet pills unless you have discussed their use with your GP.


Keep your prescription of gabapentin enacarbil in a closed package, away from direct sunlight, heat sources, and moisture. This drug should be kept at room temperature. Do not freeze or refrigerate the drug.

Be sure to keep the medicine where children and pets cannot access it. If a pet does eat any of your gabapentin, you should seek advice from your vet straight away.

Do not keep any out-of-date or unwanted drugs. Ask your GP or pharmacist for guidance on the safe disposal of medicines you no longer want.


Gabapentin enacarbil is a prescription only, anticonvulsant drug that is used to treat adult patients who are suffering from a condition known as condition called postherpetic neuralgia. This condition can arise as a complication of shingles. In addition, gabapentin enacarbil is used in patients who have an illness called primary Restless Legs Syndrome (RLS).

The medication does interact with a few other drugs and can present serious complications in certain existing medical conditions. You should discuss your medical history in full with your GP before you start using gabapentin enacarbil. In addition, throughout your treatment with this medicine you must attend your GP clinic for regular updates to make sure that the drug is working properly and to discuss any unwanted effects that it may be causing.

Patients should not that gabapentin enacarbil cannot cure either of the illnesses that it is prescribed to treat. The medicine is only effective in controlling some of the symptoms that these conditions cause.