Gabapentin is used to help control partial seizures (convulsions) in the treatment of epilepsy. This medicine cannot cure epilepsy and will only work to control seizures for as long as you continue to take it. Gabapentin is also used to manage a condition called postherpetic neuralgia, which is pain that occurs after shingles.
Gabapentin works in the brain to prevent seizures and relieve pain for certain conditions in the nervous system. It is not used for routine pain caused by minor injuries or arthritis. Gabapentin is an anticonvulsant.
This medicine is available only with your doctor’s prescription.
Gabapentin
- Class: Anticonvulsant / Neuropathic pain agent
- Brand names: Neurontin, Gralise, Horizant (gabapentin enacarbil)
- Structure: Analog of γ-aminobutyric acid (GABA), but does not bind directly to GABA receptors
Mechanism of Action
- Binds to the α2δ subunit of voltage-gated calcium channels in the central nervous system
- Reduces calcium influx → decreases release of excitatory neurotransmitters (glutamate, norepinephrine, substance P)
- Net effect: stabilizes nerve activity and reduces abnormal excitability
Approved Uses
- Partial (focal) seizures – adjunct therapy
- Postherpetic neuralgia (PHN) – nerve pain after shingles
Common Off-label Uses
- Diabetic neuropathy
- Fibromyalgia
- Anxiety disorders
- Restless legs syndrome
- Alcohol withdrawal and craving reduction
- Migraine prophylaxis
Adverse Effects
- Common: dizziness, somnolence, ataxia, peripheral edema, fatigue
- Serious: suicidal ideation (rare), respiratory depression (especially with opioids), misuse potential
Pharmacokinetics
- Absorption: Nonlinear; bioavailability decreases at higher doses
- Elimination: Excreted unchanged by kidneys (requires dose adjustment in renal impairment)
- Half-life: ~5–7 hours
Take this medicine only as directed by your doctor. Do not take more of it, do not take it more often, and do not take it for a longer time than your doctor ordered. To do so may increase the chance of side effects.
Proper Use of Taking Gabapentin
This medicine comes with a Medication Guide. Read and follow the instructions carefully. Ask your doctor if you have any questions.
If you are using Gralise® tablets:
- These should be taken with the evening meal.
- Swallow the tablet whole. Do not crush, break, or chew it.
For patients with epilepsy who take gabapentin three times per day, do not allow more than 12 hours to pass between any 2 doses. The medicine works best if a constant amount is in the blood.
Neurontin® capsules, tablets, and solution may be taken with or without food.
You may break the scored Neurontin® tablets into 2 pieces, but make sure you use the second half of the tablet as the next dose. Do not use the half-tablet if the whole tablet has been cut or broken after 28 days. Ask your doctor or pharmacist if you have any questions.
Swallow the capsule whole with plenty of water. Do not open, crush, or chew it.
Measure the oral liquid using a marked measuring spoon, oral syringe, or medicine cup. The average household teaspoon may not hold the right amount of liquid.
If you take an antacid that contains aluminum or magnesium, wait at least 2 hours before taking gabapentin. Some examples of these antacids are Di-Gel®, Gaviscon®, Gelusil®, Maalox® and Mylanta®.
Only use the brand of this medicine that your doctor prescribed. Different brands may not work the same way.
Dosing of Taking Gabapentin
The dose of this medicine will be different for different patients. Follow your doctor’s orders or the directions on the label. The following information includes only the average doses of this medicine. If your dose is different, do not change it unless your doctor tells you to do so.
The amount of medicine that you take depends on the strength of the medicine. Also, the number of doses you take each day, the time allowed between doses, and the length of time you take the medicine depend on the medical problem for which you are using the medicine.
- For oral dosage forms (capsules, liquid, and tablets):
- For epilepsy:
- Adults and children 12 years of age and older—At first, 300 milligrams (mg) 3 times per day. Your doctor may adjust your dose as needed and tolerated. However, the dose is usually not more than 1800 mg per day (600 mg 3 times per day).
- Children 3 to 11 years of age—Dose is based on body weight and must be determined by your doctor. The starting dose is 10 to 15 milligrams (mg) per kilogram (kg) of body weight per day and divided in 3 doses. Your doctor may adjust your dose as needed and tolerated.
- Children younger than 3 years of age—Use and dose must be determined by your doctor.
- For postherpetic neuralgia:
- Adults— At first, 300 milligrams (mg) as a single dose in the evening. Your doctor may adjust your dose as needed and tolerated. However, the dose is usually not more than 1800 mg per day.
- Children—Use and dose must be determined by your doctor.
- For epilepsy:
Missed Dose
If you miss a dose of this medicine, take it as soon as possible. However, if it is almost time for your next dose, skip the missed dose and go back to your regular dosing schedule. Do not double doses.
The Dosages of Taking Gabapentin for Off-Label Usages
Dosing is individualized depending on renal function, age, and tolerability. Always titrated gradually to reduce dizziness/somnolence.
| Condition (Off-label) | Typical Dose Range | Notes |
|---|---|---|
| Diabetic neuropathy | 900–3600 mg/day (divided TID) | Start 300 mg QHS → titrate; effective ≥1800 mg/day in many patients |
| Fibromyalgia | 1200–2400 mg/day (divided TID) | Pregabalin usually first choice, but gabapentin used if not tolerated |
| Trigeminal neuralgia | 900–3600 mg/day | Alternative to carbamazepine/oxcarbazepine |
| Restless legs syndrome (RLS) | 300–1800 mg at bedtime | Often effective at lower doses; gabapentin enacarbil (Horizant) FDA-approved at 600 mg QHS |
| Migraine prophylaxis | 900–2400 mg/day | Evidence mixed; used when standard preventives fail |
| Hot flashes / menopausal symptoms | 900–2400 mg/day (divided TID) | Often 300 mg TID; some use 300 mg QHS |
| Alcohol withdrawal / relapse prevention | 900–1800 mg/day (divided TID) | Helps anxiety, insomnia, craving |
| Opioid withdrawal | 900–2100 mg/day | Used short-term during taper/detox |
| Pruritus (CKD, cholestasis, others) | 300–1800 mg/day (divided) | Lower doses often effective |
| Chronic cough (refractory) | 900–1800 mg/day | Reduces cough reflex hypersensitivity |
Titration Strategy
- Start low: 300 mg once daily (often at bedtime)
- Increase slowly: add 300 mg every 1–3 days
- Target: usually 900–1800 mg/day, sometimes up to 3600 mg/day (max studied dose)
- Divide doses: 2–3 times daily (due to short half-life)
Renal Adjustment
-
eGFR <60 mL/min → lower dose or extend dosing interval (since gabapentin is renally cleared).