Gabapentin (Neurontin®, Horizant®)

Author: OncoLink Team
Last Reviewed: April 03, 2023

Pronounce: GAB-a-PEN-tin

Classification: Anti-Convulsant

About: Gabapentin (Neurontin®, Horizant®)

Gabapentin is in a class of medications called anti-convulsants, which means that it was originally developed to treat seizures. Gabapentin is still used to treat seizure disorders, but it is also often used to treat neuropathic pain. Neuropathic pain is pain that is related to injury or inflammation of nerves. If nerves are injured by trauma (including surgery and radiation), infection, nerve compression by tumor, or chemotherapy damage, gabapentin can often help to relieve the associated pain. No one knows the exact mechanism by which gabapentin treats neuropathic pain, but it may be related to how nerves send their pain signals to the brain.

How to Take Gabapentin

Gabapentin comes as a capsule, a tablet, an extended-release (long-acting) tablet, and an oral solution (liquid) to take by mouth with water. Capsules and tablets should be taken whole; do not chew, break or open. The medication is often prescribed 3 times a day and should be taken at evenly spaced times throughout the day and night. If you are taking the extended-release version, follow the directions given by your healthcare provider and take the medication with food.

It is important to make sure you are taking the correct amount of medication every time. Before every dose, check that what you are taking matches what you have been prescribed.

This medication can interact with other medications; be sure to tell your healthcare provider about all medications and supplements you are using. The levels of this medication are affected by Maalox® (antacid). Gabapentin should be taken at least 2 hours after taking Maalox. You should not drink alcohol, particularly with the extended-release formula, as this affects how it is released. This medication can cause slowed breathing when taken with central nervous system depressants such as opioids. You should not drive or operate heavy machinery while taking this medication until you know it is safe to do so.

Storage and Handling

Store this medication at room temperature in the original container. If you prefer to use a pillbox, discuss this with your oncology pharmacist. Ask your oncology team where to return any unused medication for disposal. Do not flush down the toilet or throw in the trash.

Where do I get this medication?

Gabapentin is available through retail or mail order pharmacy. Your oncology team will work with your prescription drug plan to identify an in-network, retail or mail-order pharmacy for medication distribution.

Insurance Information

This medication may be covered under your prescription drug plan. Patient assistance may be available to qualifying individuals depending upon prescription drug coverage. Co-pay cards, which reduce the patient co-pay responsibility for eligible commercially (non-government sponsored) insured patients, may also be available. Your care team can help you find these resources if they are available.

Possible Side Effects of Gabapentin

This medication is given to manage and/or prevent side effects of your cancer treatment. If you are having side effects from this medication, you should talk to your team about if this medication is necessary for your treatment or if there are other options to help manage the side effect this medication is treating. These are some of the most common side effects:

Sleepiness (Somnolence)

Feeling sleepy, drowsy, or lightheaded may accompany the use of gabapentin. Some people just don't "feel like themselves" on this medication. Avoid driving or any other potentially dangerous tasks that require your concentration and a clear head until you know how the medication will affect you. Avoid alcohol or other sedatives while using gabapentin unless they are specifically prescribed by your doctor.

Allergic Reaction

This medication can cause an allergic reaction called DRESS (drug reaction with eosinophilia and systemic symptoms) and multi-organ hypersensitivity. Report any signs and symptoms of allergic reaction, including rash, fever, or swollen lymph nodes (swollen glands) to your healthcare team immediately.

Suicidal Behavior/Ideation

Gabapentin may increase your risk for suicidal thoughts and behaviors. Your caregiver should be aware of this concern as well. Report any changes or worsening of mood or behavior or suicidal (self-harm) thoughts to your healthcare team immediately.


Patients who have a history of seizures should tell their provider before starting this medication, even if gabapentin is not being prescribed for seizures. Increased seizure frequency may occur in patients with seizure disorders if gabapentin is abruptly discontinued. Take this medication as prescribed and do not stop taking it without first talking with your care team. If you have any signs or symptoms of a seizure, notify your provider immediately.


If someone intentionally or accidentally takes too much gabapentin, they may experience double vision, slurred speech, drowsiness, or diarrhea. This happens very rarely. If you suspect that you or someone you know has taken an overdose of gabapentin, call 911 immediately. Overdose of gabapentin is an emergency situation and needs immediate attention.

Reproductive Concerns

Exposure of an unborn child to this medication could cause birth defects, so you should not become pregnant while on this medication. If you are pregnant or become pregnant, discuss the risks and benefits of continuing this medication with your care provider. You should consult with your healthcare team before breastfeeding while receiving this medication.


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