Gabapentin dosage, forms, and strengths

Gabapentin (brand name: Neurontin) is a generic prescription drug that is FDA-approved as an add-on treatment with other medications for partial seizures in those with epilepsy. It can also be used to treat nerve pain from postherpetic neuralgia (a complication of shingles). Gabapentin is frequently prescribed off-label for many other conditions, such as diabetic peripheral neuropathy, fibromyalgia, and alcohol dependence. 

Gabapentin is typically prescribed as a generic, but the drug is also available under the brand names Neurontin and Gralise. Some patients may be prescribed drugs very similar to gabapentin—such as Horizant (gabapentin enacarbil) or Lyrica (pregabalin)—instead of gabapentin. 

Gabapentin is taken as a tablet, capsule, or oral liquid. Dosing will depend on the condition being treated, age of the person being treated, and kidney function. The usual dose for epilepsy starts at 300 mg on the first day. The dose can then be increased until an effective dose is reached, which is usually 300 to 600mg taken three times per day.

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Gabapentin dosage forms and strengths

Gabapentin is taken by mouth as a tablet, capsule, or oral solution.

• Tablets: 600 or 800 mg per tablet

• Capsules: 100, 300, or 400 mg per capsule

• Liquid: 250 mg per 5 milliliters (ml) oral liquid

Gabapentin dosage for adults

For adults, the gabapentin dosage can vary widely depending on the condition being treated. Upon starting treatment with gabapentin, the starting dose may be 100 to 300 mg per day and steadily increase until an effective dose is reached. The maximum dosage will depend on the condition being treated.

• Standard gabapentin dosage for adults: 300-600 mg taken three times per day.

• Maximum gabapentin dosage for adults: 1200 mg taken three times per day for a maximum daily dose of 3600 mg.

Gabapentin dosage for children

Gabapentin is FDA-approved as a secondary treatment for partial seizures in children 3 years or older with epilepsy. The use of gabapentin in children for any other medical condition is not FDA-approved. Dosing will be determined by both the child’s age and weight.

Gabapentin dosage for partial seizures

Gabapentin is FDA-approved as adjunctive therapy for partial seizures in adults and children 3 years of age or older.

• Standard gabapentin dosage for adults: 300 to 600 mg taken three times per day by mouth.

• Maximum gabapentin dosage for adults: 3600 mg daily in three divided doses.

• Renally impaired patients (kidney disease)—dose amount and dose frequency adjustment:

  • Creatinine clearance of 30-59 ml/min: 200 to 700 mg twice per day

  • Creatinine clearance of 16-29 ml/min: 200 to 700 mg once per day

  • Creatinine clearance of 15 ml/min or less: 100 to 300 mg once per day decreased proportionately (1/15 per whole number value) for each decrease in creatinine clearance

  • Hemodialysis: dose is dependent on estimated creatinine clearance; a supplemental dose of 125 to 350 mg is given after dialysis 

Gabapentin dosage for nerve pain due to shingles (postherpetic neuralgia)

Gabapentin is FDA-approved to treat postherpetic neuralgia, that is, neuropathic pain due to shingles (herpes zoster).

• Standard gabapentin dosage for adults: 300 to 600 mg taken three times per day by mouth.

• Maximum gabapentin dosage for adults: 1800 mg daily in three divided doses.

• Renally impaired patients (kidney disease): See dosage for renal impaired patients above

Gabapentin dosage for neuropathic pain

Gabapentin is most frequently prescribed off-label to treat nerve pain (neuralgia) due to nerve damage (neuropathy), compression, or irritation.

• Standard gabapentin dosage for adults: 300 to 1200 mg taken three times per day by mouth.

• Maximum gabapentin dosage for adults: 3600 mg daily in three divided doses.

• Renally impaired patients (kidney disease): See dosage for renal impaired patients above

Gabapentin dosage for fibromyalgia

Gabapentin is used off-label to reduce fatigue, provide pain relief, and improve sleep in patients with fibromyalgia.

• Standard gabapentin dosage for adults: 600 mg twice daily and 1200 mg at bedtime.

• Maximum gabapentin dosage for adults: 2400 mg daily.

• Renally impaired patients (kidney disease): See dosage for renal impaired patients above

Gabapentin dosage for alcohol dependence

Gabapentin is widely used off-label to reduce insomnia and cravings in people with alcohol use disorder, particularly those in the maintenance phase of alcohol abstinence.

• Standard gabapentin dosage for adults: 300 to 600 mg taken three times per day by mouth.

• Maximum gabapentin dosage for adults: 1800 mg daily in three divided doses.

• Renally impaired patients (kidney disease): See dosage for renal impaired patients above

Gabapentin dosage for pets

You should not give gabapentin to animals unless a veterinarian has given the animal a prescription for gabapentin. Veterinarians frequently prescribe gabapentin to treat seizures or chronic nerve pain in pets and large animals. The recommended dose is 5-10 mg per kilogram of body weight (2.3-4.5 mg/lb) every 12 hours, but dosing will vary between veterinarians. Gabapentin dosages can vary from 3 to 11 mg per kilogram (1.4 to 5 mg per pound) as an analgesic to 10 to 30 mg per kilogram (4.5 to 13.6 per pound) as an anticonvulsant. As with people, the dose may start small and steadily increase until an effective dose is reached. 

How to take gabapentin

Gabapentin is usually taken by mouth three times per day. In special circumstances, such as when the drug is first started or in patients with kidney problems, gabapentin is taken less frequently.

• Take your medicine as directed. The dose may change until the most effective dose amount is reached. 

• If you have epilepsy, do not allow more than 12 hours to pass between doses.

• Gabapentin can be taken with or without food.

Tablet 

• Swallow the tablet whole with a glass of water. Do not crush, break, or chew it.

• If you break a tablet into two pieces, use the second half as your next dose. Discard any unused half-tablet after 28 days.

Capsule

• Swallow the capsule whole with a glass of water. Do not open, crush, or chew it.

• If it’s too difficult to swallow the capsule, the patient or a caregiver can carefully open the capsule and sprinkle the contents into a small cup of water, juice, or apple sauce and give the dose that way.

Oral liquid

• Measure the oral liquid with a syringe or medicine cup that has millimeter markings. Gabapentin oral suspension usually comes with a 12 ml dosing syringe. 

• Shake the closed bottle well before each use.

• Remove the child-proof cap from the bottle. 

• Make sure the syringe adapter has been pushed into the bottle opening. If not, fully insert the syringe adapter into the bottle opening.

• Push the syringe plunger all the way down to the tip.

• Insert the syringe tip into the adapter.

• Turn the bottle and syringe upside down.

• Slowly draw out enough liquid to the correct milliliter mark.

• Turn the bottle back to the upright position.

• Remove the syringe and place the tip in the mouth.

• Slowly empty the contents into the mouth and swallow.

• Securely fasten the child-safety cap back on the bottle.

Missed dose

• If you miss a dose of gabapentin, take the missed dose as soon as you remember. Take the next dose at its scheduled time. If it is almost time for the next dose, skip the missed dose and take the next dose at its scheduled time. Do not take extra medicine to make up for a missed dose. 

• If you are taking gabapentin for seizures, ask your doctor or pharmacist for directions on how to handle a missed dose.

When taking gabapentin, you may want to consider the following safety and effectiveness tips:

• Before taking gabapentin, please read the Medication Guide that comes with it. Ask your pharmacist for a copy if you do not have one.

• Store the medicine in a closed container at room temperature (59˚-86˚F), away from heat, moisture, and direct light. 

• Store the oral liquid in the refrigerator (36˚-46˚F). Do not freeze the solution.

• Unless directed by a doctor, do not take gabapentin with alcohol or medicines that cause drowsiness.

• If you take an antacid containing aluminum or magnesium such as Maalox, Mylanta, or Gaviscon, wait at least two hours before taking a gabapentin dose.

• When taking gabapentin as a liquid, use the metered syringe or cup supplied with the medicine to accurately measure the dose. If you lose the syringe or cup, your pharmacy can provide a replacement at no cost.

• In an emergency when you can’t replace a lost measuring device, you can temporarily use a kitchen measuring spoon to take a dose of gabapentin oral suspension, but NEVER use a spoon that you eat with or a measuring cup. One full teaspoon is nearly equal to 5 ml of liquid. One full tablespoon equals about 15 ml of liquid.

• If you are taking the oral liquid, ask your pharmacist for the correct milliliter dose.

• For each dose, record the time in a diary or schedule to ensure that the next dose is not given too early or too late.

• If taking gabapentin causes an upset stomach, try taking it with food.

• If breastfeeding, ask your doctor about taking gabapentin. 

• Gabapentin can slow your thinking, decrease coordination, and cause drowsiness, so do not drive, operate machinery, or engage in dangerous activities if you feel tired, dizzy, or slow. 

Gabapentin dosage FAQs

How long does it take gabapentin to work?

The starting dose of gabapentin is low. The dose amount and frequency will be steadily increased each day until an effective dose is reached, a process called titration. For most conditions, it typically takes one to two weeks after the starting dose to notice the effects of gabapentin.

How long does gabapentin stay in your system?

For people with healthy kidneys, gabapentin is typically taken every eight hours. Each dose reaches its maximum concentration in the body in two to three hours. 

The kidneys rapidly clear gabapentin from the body. The rate at which the body clears gabapentin is measured by its half-life, which is the amount of time it takes for the body to clear half the gabapentin in the body. The half-life of gabapentin in children is about five hours. In adults, gabapentin’s half-life is five to seven hours. 

Because gabapentin is cleared by the kidneys, the drug stays in the system longer in patients with impaired renal function. Both the dose amount and dose frequency may need to be adjusted by the prescribing physician.

What happens if I miss a dose of gabapentin?

If you miss a dose of gabapentin, take the missed dose as soon as you remember. Take the next dose at its scheduled time. If it is almost time for the next dose, skip the missed dose and take the next dose at its scheduled time. Do not take extra medicine to make up for a missed dose. If you are taking gabapentin for seizures, ask your doctor, pharmacist, or other healthcare professional for instructions for handling a missed dose. In patients with epilepsy, missing a dose for longer than 12 hours increases the risk of seizures.

How do I stop taking gabapentin?

Gabapentin should not be stopped unless directed by a physician. Patients may experience withdrawal symptoms, such as agitation, anxiety, restlessness, nausea, and flu-like symptoms, if gabapentin is abruptly discontinued after taking it for longer than six weeks. If gabapentin is being taken to prevent seizures, abrupt discontinuation of the drug may cause severe seizures. When it’s time to stop taking gabapentin, your doctor may gradually taper your dose across seven days.

Seek immediate medical attention if you experience serious side effects such as mood or behavioral changes, suicidal thoughts, breathing problems, or signs of a hypersensitivity reaction such as hives, difficulty breathing, swollen glands, or fever.

What can be used instead of gabapentin?

Because of side effects, medical conditions, or other reasons, gabapentin may not be right for everyone. The good news is that there are alternative and effective medications for most conditions treated by gabapentin. These medications include anticonvulsants, analgesics, tricyclic antidepressants, selective serotonin reuptake inhibitors (SSRIs) such as Cymbalta (duloxetine), and selective serotonin and norepinephrine reuptake inhibitors (SNRIs) such as Savella (milnacipran).

What is the maximum dosage for gabapentin?

The maximum dosage for gabapentin depends on the condition being treated. For most conditions, this maximum ranges between 2,400 mg and 3,600 mg per day.

What interacts with gabapentin?

Foods do not affect the bioavailability or effectiveness of gabapentin. However, if gabapentin is causing side effects such as upset stomach, constipation, or diarrhea, changes in the diet may be required.

Because gabapentin slows activity in the brain, it may cause certain side effects, such as drowsiness, dizziness, sedation, somnolence, and impaired coordination (ataxia). Gabapentin may interact with similar substances or drugs that depress the central nervous system, such as alcohol, cannabinoids, sedatives, antihistamines, anxiety medications, opioids, and other antiepileptic drugs. Not all of these drugs are to be avoided outright, but their use may be modified by your physician. When gabapentin is taken with any of these drugs, patients need to avoid the medication or be cautious while driving, operating machinery, or engaging in potentially dangerous activities.

Patients should also exercise caution when taking antacids that contain aluminum or magnesium salts. Aluminum and magnesium can decrease the concentration of gabapentin in the body, which can reduce the effectiveness of the medication. As a general rule, wait at least two hours after taking an antacid before taking a dose of gabapentin.

Resources:

• Gabapentin dosing, Epocrates

• Gabapentin compound summary, National Library of Medicine

• Gabapentin, StatPearls

• Gabapentin and amantadine for chronic pain: is your dose right?, Today's Veterinary Practice

• Neurontin FDA prescribing information, FDA

• Neurontin medication guide, Pfizer