Gabapentin

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Gabapentin

Definition

Purpose

Description

Recommended dosage
For epilepsy

Definition

Gabapentin is an antiseizure medication. It is sold in the United States under the trade name Neurontin.

Gabapentin is used in combination with other antiseizure (anticonvulsant) drugs to manage partial seizures with or without generalization in individuals over the age of 12. Gabapentin can also be used to treat partial seizures in children between the ages of three and 12. Off-label uses (legal uses not specifically approved by the U.S. Food and Drug Administration [FDA]) include treatment of severe, chronic pain caused by nerve damage, such as occurs in shingles, diabetic neuropathy, multiple sclerosis, or post-herpetic neuralgia. Studies are also looking at using gabapentin to treat bipolar disorder (also known as manic-depressive disorder), with the most recent work focusing on using the drug as a prophylaxis. It has not shown good effectiveness as an acute treatment for bipolar disorder.

Description

Brain cells normally transmit nerve impulses from one cell to another by secreting chemicals known as neurotransmitters. Gabapentin is chemically related to a naturally occurring neurotransmitter called GABA (gamma-amino butyric acid). The actual mechanism of action by which gabapentin acts in the brain to control seizures and treat pain is not known, although it appears to alter the action of nerve cells.

Gabapentin was approved for use in the United States in 1993. A liquid formulation was approved for use in 2000. Use in children ages three to 12 was also approved by the FDA in 2000.

Gabapentin is available in 100-, 300-, and 400-mg capsules; in 600- and 800- mg tablets; and in a liquid solution containing 250 mg per 5 ml.

Recommended dosage
For epilepsy

People over the age of 12 can begin with an initial does of 300 mg three times a day, which can be gradually increased as necessary, usually to no more than 1,800 mg daily. For children ages three to 12, the dose is based on body weight, initially 10-15 mg per kilogram per day in three separate doses. The physician may choose to increase this dose as necessary. For a child under the age of three, the decision about use and dosage will be made by the doctor. For older adults, the maximum daily dose does not usually exceed 600 mg three times a day.

For pain

This dosing involves a gradual increase, with an initial does of 300 mg on the first day, followed by 300 mg twice on the second day, and 300 mg three times on day three. A physician may increase this dose to a maximum daily dose of 1,800 mg.

Precautions

Women who are breast-feeding and people who have decreased kidney functioning should discuss the risks and benefits of this drug with their physician. Women who are or wish to become pregnant will also require a careful assessment of the risks and benefits of gabapentin.

Patients should not suddenly discontinue gabapentin, which can result in an increased risk of seizures. If the medication needs to be discontinued, the dosage should be reduced gradually over a week.

Until an individual understands the effects that gabapentin may have, he or she should avoid driving,

KEY TERMS

Diabetic neuropathy —A condition in which the nerve endings, particularly in the legs and feet, become less sensitive. Minor injuries, such as blisters or callouses, are not felt and can thus become infected and become more serious problems.

Multiple sclerosis —A disease characterized by patches of hardened tissue in the brain or spinal cord, paralysis, and/or muscle tremors.

Neuralgia —Pain that extends along the course of a nerve.

Neurotransmitter —A chemical in the brain that transmits messages between neurons, or nerve cells.

operating dangerous machinery, or participating in hazardous activities. Alcohol should be avoided while taking gabapentin.

Side effects

Patients who experience the following side effects of gabapentin should check with their doctor immediately. More common side effects are unsteadiness, clumsiness, and uncontrollable back-and-forth eye movements or eye rolling. Less common side effects include depression , irritability, other mood changes or changes in thinking, and decreased memory. Rare side effects include pain in the lower back or side, difficulty urinating, fever and/or chills, cough, or hoarseness.

Children under age 12 who have the following more common side effects should see a doctor immediately: aggressive behavior, irritability, anxiety , difficulty concentrating and paying attention, crying, depression, mood swings, increased emotionality, hyperactivity, and suspiciousness or distrust.

Multiple side effects often occur when a patient starts taking gabapentin. While these side effects usually go away on their own, if they last or are particularly troublesome, the patient should consult a doctor. More common side effects that occur when first starting to take gabapentin include blurred or double vision; muscle weakness or pain; swollen hands, feet, or legs; trembling or shaking; and increased fatigue or weakness. Less common side effects that occur when initiating gabapentin treatment include back pain, constipation, decreased sexual drive, diarrhea, dry mouth and eyes, frequent urination, headache, indigestion, low blood pressure, nausea, ringing in the ears, runny nose, slurred speech, difficulty thinking and sleeping, weight gain, twitching, nausea and/or vomiting, weakness.

Interactions

Antacids can decrease gabapentin levels in the blood. They should be taken at least two hours before taking gabapentin.

Resources

BOOKS

Ellsworth, Allan J. Mosby’s Medical Drug Reference. St. Louis: Mosby, Incorporated, 1999.

Mosby’s Drug Consult. St. Louis: Mosby, Incorporated, 2002.

PERIODICALS

Vieta, Eduard, et al. “A Double-Blind, Randomized Placebo-Controlled, Prophylaxis Study of Adjunctive Gabapentin for Bipolar Disorder.” Journal of Clinical Psychiatry 67 (2006): 473–77.