Gabapentin belongs to the class of medications called anti-epileptics. It is used in combination with other seizure control medications to manage and prevent seizures associated with epilepsy. Gabapentin does not cure epilepsy and only works to control seizures as long as the medication is taken. Gabapentin works by affecting the transmission of nerve signals in the brain.

This medication may be available under multiple brand names and/or in several different forms. Any specific brand name of this medication may not be available in all of the forms or approved for all of the conditions discussed here. As well, some forms of this medication may not be used for all of the conditions discussed here.

Your doctor may have suggested this medication for conditions other than those listed in these drug information articles. If you have not discussed this with your doctor or are not sure why you are taking this medication, speak to your doctor. Do not stop taking this medication without consulting your doctor.

Do not give this medication to anyone else, even if they have the same symptoms as you do. It can be harmful for people to take this medication if their doctor has not prescribed it.

The usual recommended adult dose of gabapentin begins with 300 mg 3 times daily. Your doctor may increase your dosage depending on how well it works and how well you tolerate it. The usual maximum daily dose is a total of 900 mg to 1,800 mg divided into 3 equal doses. Occasionally, it may be necessary to increase the total daily dose to as much as 2,400 mg, however higher doses generally cause more side effects. Gabapentin may be taken with or without food.

Many things can affect the dose of medication that a person needs, such as body weight, other medical conditions, and other medications. If your doctor has recommended a dose different from the ones listed here, do not change the way that you are taking the medication without consulting your doctor.

This medication should not be stopped suddenly, as seizures may return. If you feel it is necessary to stop this medication, discuss the most appropriate schedule with your doctor.

It is important that this medication be taken exactly as prescribed by your doctor. If you miss a dose, take it as soon as possible and continue with your regular schedule. If it is less than 4 hours until your next scheduled dose, skip the missed dose and continue with your regular dosing schedule. To prevent breakthrough seizures, no more than 12 hours should pass between doses. Do not take a double dose to make up for a missed one. If you are not sure what to do after missing a dose, contact your doctor or pharmacist for advice.

Store this medication at room temperature and keep it out of the reach of children.

100 mg
Each hard gelatin capsule, with white opaque body and cap, printed with "GA100" on one side and a logo on the other, contains 100 mg of gabapentin. Nonmedicinal ingredients: gelatin, lactose, maize starch, red iron oxide, talc, titanium dioxide, and yellow iron oxide. Gluten-free.

300 mg
Each hard gelatin capsule, with white opaque body and cap, printed with "GA300" on one side and a logo on the other, contains 300 mg of gabapentin. Nonmedicinal ingredients: gelatin, lactose, maize starch, red iron oxide, talc, titanium dioxide, and yellow iron oxide. Gluten-free.

400 mg
Each hard gelatin capsule, with orange opaque body and cap, printed with "GA400" on one side and a logo on the other, contains 400 mg of gabapentin. Nonmedicinal ingredients: gelatin, lactose, maize starch, red iron oxide, talc, titanium dioxide, and yellow iron oxide. Gluten-free.

Tablet

600 mg
Each white, oval, biconvex, film-coated tablet engraved "GAB" over partial bisect "600" on one side and "APO" on the other contains 600 mg of gabapentin. Non-medicinal ingredients: copovidone, hydroxypropyl cellulose, hydroxypropyl methylcellulose, magnesium stearate, polyethylene glycol, purified water, and titanium dioxide.

800 mg
Each white, oval, biconvex, film-coated tablet engraved "GAB" over partial bisect "800" on one side and "APO" on the other contains 800 mg of gabapentin. Non-medicinal ingredients: copovidone, hydroxypropyl cellulose, hydroxypropyl methylcellulose, magnesium stearate, polyethylene glycol, purified water, and titanium dioxide.

Do not take gabapentin if you are allergic to gabapentin or any ingredients of this medication.

Many medications can cause side effects. A side effect is an unwanted response to a medication when it is taken in normal doses. Side effects can be mild or severe, temporary or permanent.

The side effects listed below are not experienced by everyone who takes this medication. If you are concerned about side effects, discuss the risks and benefits of this medication with your doctor.

The following side effects have been reported by at least 1% of people taking this medication. Many of these side effects can be managed, and some may go away on their own over time.

Contact your doctor if you experience these side effects and they are severe or bothersome. Your pharmacist may be able to advise you on managing side effects.

• dizziness
• drowsiness
• fatigue
• swelling of feet or ankles
• trouble sleeping

Although most of the side effects listed below don't happen very often, they could lead to serious problems if you do not check with your doctor or seek medical attention.

Check with your doctor as soon as possible if any of the following side effects occur:

• abnormal heartbeat or heart palpitations
• agitation
• changes in blood sugar and decreased blood sugar control (low blood sugar – cold sweat, cool pale skin, headache, fast heartbeat, weakness; high blood sugar – frequent urination, increased thirst, excessive eating, unexplained weight loss, poor wound healing, infections, fruity breath odour)
• chest pain
• confusion
• hallucinations (e.g., seeing or hearing things that aren't there)
• inability to control urination
• poor coordination
• rapid or pounding heartbeat (palpitations)
• ringing in the ears
• signs of depression (e.g., poor concentration, changes in weight, changes in sleep, decreased interest in activities, thoughts of suicide)
• symptoms of low sodium in the blood (e.g., tiredness, weakness, confusion, achy, stiff or uncoordinated muscles)
• symptoms of liver problems (e.g., abdominal pain, persistent vomiting, feeling unwell, fever, itching, yellowing of the skin and eyes, dark urine)
• unexplained muscle pain or tenderness, muscle weakness, dark urine with nausea or vomiting
• unusual changes in mood

Stop taking the medication and seek immediate medical attention if any of the following occur:

• hallucinations (seeing or hearing things that aren't there)
• loss of consciousness
• signs of a serious allergic reaction (e.g., swelling of face or throat, hives, or difficulty breathing)
• signs of a severe skin reaction such as blistering, peeling, a rash covering a large area of the body, a rash that spreads quickly, or a rash combined with fever or discomfort
• slow, shallow, or weak breathing
• thoughts of hurting yourself or others
• worsening seizures

Some people may experience side effects other than those listed. Check with your doctor if you notice any symptom that worries you while you are taking this medication.

Before you begin using a medication, be sure to inform your doctor of any medical conditions or allergies you may have, any medications you are taking, whether you are pregnant or breast-feeding, and any other significant facts about your health. These factors may affect how you should use this medication.

Alcohol and other medications that cause drowsiness: People taking this medication should not combine it with alcohol and avoid combining it with other medications that cause drowsiness, such as narcotic pain relievers or sedatives. Doing so can cause additional drowsiness and reduced breathing, which can be dangerous and possibly life threatening.

Difficulty breathing: Gabapentin can cause serious and life-threatening breathing problems. If you have breathing or lung problems, decreased kidney function, are taking other medications that can slow breathing, or if you are a senior, you are more at risk of experiencing breathing difficulties. If you experience slowed breathing or difficulty breathing, seek immediate medical attention.

Drowsiness/reduced alertness: If you have uncontrolled epilepsy, do not drive or handle potentially dangerous machinery. Gabapentin may cause drowsiness, dizziness, or problems with coordination. Avoid any activity requiring mental alertness or physical coordination until you determine how gabapentin affects you.

Hypersensitivity syndrome: A severe allergic reaction called hypersensitivity syndrome has occurred for some people with the use of gabapentin. Stop taking the medication and get immediate medical attention if you have symptoms of a severe allergic reaction, including fever, swollen glands, yellowing of the skin or eyes, or flu-like symptoms with skin rash or blistering.

Kidney function: Kidney disease or reduced kidney function may cause this medication to build up in the body, causing side effects. If you have reduced kidney function or kidney disease, discuss with your doctor how this medication may affect your medical condition, how your medical condition may affect the dosing and effectiveness of this medication, and whether any special monitoring is needed.

Opioid overdose risk: Using gabapentin in combination with opioid pain medications such as codeine, morphine, or oxycodone can increase the risk of opioid overdose and serious side effects such as decreased breathing, sedation, dizziness, fainting, and death. People who are taking gabapentin in combination with opioids should be monitored carefully for increased side effects.

Stopping the medication: As with other medications used to control seizures, stopping gabapentin suddenly could increase the risk of seizures. Do not stop gabapentin suddenly. Ask your doctor how to safely and gradually stop the medication.

Suicidal or agitated behaviour: People taking this medication may feel agitated (restless, anxious, aggressive, emotional, and feeling not like themselves), or they may want to hurt themselves or others. If you experience these side effects or notice them in a family member who is taking this medication, contact your doctor immediately. You should be closely monitored by your doctor for emotional and behaviour changes while taking this medication.

Pregnancy: Gabapentin crosses the placenta and may harm the developing baby if it is taken by the mother while she is pregnant. It should not be used during pregnancy unless the benefits outweigh the risks. If you become pregnant while taking this medication, contact your doctor immediately.

Breast-feeding: This medication passes into breast milk. If you are a breast-feeding mother and are taking gabapentin, it may affect your baby. Talk to your doctor about whether you should continue breast-feeding.

Children: The safety and effectiveness of using this medication have not been established for children.

Seniors: Seniors are at an increased risk of side effects and may require a dose of this medication that is lower than usual due to reduced kidney function.

There may be an interaction between gabapentin and any of the following:

• alcohol
• antacids containing magnesium or aluminum
• antihistamines (e.g., cetirizine, doxylamine, diphenhydramine, hydroxyzine, loratadine)
• antipsychotics (e.g., chlorpromazine, clozapine, haloperidol, olanzapine, quetiapine, risperidone)
• azelastine
• benzodiazepines (e.g., alprazolam, diazepam, lorazepam)
• brimonidine
• buprenorphine
• buspirone
• butorphanol
• calcium carbonate
• cannabis
• chloral hydrate
• clonidine
• entacapone
• eszopiclone
• general anesthetics (medications used to put people to sleep before surgery)
• mefloquine
• methadone
• metoclopramide
• mirtazapine
• muscle relaxants (e.g., baclofen, cyclobenzaprine, methocarbamol, orphenadrine)
• nabilone
• narcotic pain relievers (e.g., codeine, hydrocodone,  morphine, oxycodone)
• orlistat
• pramipexole
• ropinirole
• rotigotine
• scopolamine
• other seizure medications (e.g., carbamazepine, clobazam, ethosuximide, levetiracetam, phenobarbital, phenytoin, primidone, topiramate, valproic acid, zonisamide)
• tapentadol
• thalidomide
• tramadol
• trazodone
• tricyclic antidepressants (e.g., amitriptyline, imipramine)
• zolpidem
• zopiclone

If you are taking any of these medications, speak with your doctor or pharmacist. Depending on your specific circumstances, your doctor may want you to:

• stop taking one of the medications,
• change one of the medications to another,
• change how you are taking one or both of the medications, or
• leave everything as is.

An interaction between two medications does not always mean that you must stop taking one of them. Speak to your doctor about how any drug interactions are being managed or should be managed.

Medications other than those listed above may interact with this medication. Tell your doctor or prescriber about all prescription, over-the-counter (non-prescription), and herbal medications you are taking. Also tell them about any supplements you take. Since caffeine, alcohol, the nicotine from cigarettes, or street drugs can affect the action of many medications, you should let your prescriber know if you use them.