Gabapentin
Gabapentin
Definition
Gabapentin is indicated to be used in combination with other anti-seizure (anticonvulsant) drugs for the management of partial seizure types. Gabapentin should not be used alone for the treatment of seizures unless the patient cannot tolerate other anticonvulsant drugs. This medication can also be used for the treatment of certain syndromes associated with nerve (neuropathic) pain (diabetic neuropathy , postherpetic neuralgia), pain associated with multiple sclerosis, neuropathic cancer pain, trigeminal neuralgia, and bipolar mood disorder. Gabapentin is also known as Neurontin.
Description
Gabapentin was introduced in 1994 as an anticonvulsant medication. Other medications in the anticonvulsant class include phenytoin , carbamazepine , phenobarbital, valproic acid, topiramate, and lamotrigine. Gabapentin's structure is similar to that of gamma-aminobutiric acid (GABA), which is a chemical found in the central nervous system (brain and spinal cord) that decreases firing of neurons leading to a decrease in seizure activity. Despite this structural similarity, gabapentin does not interact with GABA receptors and its exact mechanism of action for either epilepsy or pain is not known.
Gabapentin is a relatively recent addition to the arsenal of drugs used in the treatment of neuropathic pain. Traditionally, tricyclic antidepressants (amitriptyline , nortriptyline, desipramine) have been used as first-line agents. It takes one to three weeks for either gabapentin or tricyclic antidepressants (TCAs) to provide relief of pain after starting treatment. Gabapentin appears to be a safer agent to use than TCAs, especially in elderly patients and patients on multiple other medications. One of the disadvantages of gabapentin over TCAs is its higher cost.
Recommended Dosage
Adults and children over 12 years of age
MANAGEMENT OF PARTIAL SEIZURE TYPES.
Therapy should be started at a dose of 300 mg, three times daily. The dose can be increased to 1, 800 mg/day in three divided doses. Some patients may need even higher doses to control their seizures. Doses up to 3, 600 mg per day have been well tolerated in research studies.
TREATMENT OF NEUROPATHIC PAIN.
Dosages of 300-3, 600 mg/day have been effective in research studies. However, optimal dosage appears to be 1, 200-2, 400 mg/day divided in three doses.
TREATMENT OF BIPOLAR DISORDER.
Optimal dose has not been well established. Doses up to 4, 800 mg/day have been used.
Children less than 12 years of age
Dosage varies due to the child's size, weight, and extent of condition. Parents should ask their physician about appropriate dosage levels for their child.
Administration
To minimize side effects, the first dose should be taken at bedtime. Capsules should not be chewed or crushed. Patients should avoid taking antacids (Mylanta, Maalox) at the same time as gabapentin. Doses should be taken at even intervals, and if a dose is missed, it should be taken as soon as remembered. However, double-doses can be hazardous, and should be avoided.
Precautions
Gabapentin should be used with caution by breast-feeding mothers, children under 12 years of age (because of a lack of safety and efficacy studies in this population), and patients with impaired kidney function.
Gabapentin has resulted in fetal abnormalities in mice, rats, and rabbit offsprings. There are no current studies on gabapentin use in pregnant women. This drug should only be used during pregnancy if potential benefits justify the risk to the baby.
This medication should not be discontinued suddenly because of the possibility of increased frequency of seizures. Gabapentin doses should be decreased gradually over a period of at least one week.
Gabapentin may cause drowsiness and dizziness. Alcoholic beverages may intensify these effects and their intake should be limited. Patients should use caution when driving, operating dangerous machinery, or performing activities requiring alertness.
A patient experiencing any of the following should contact their physician or pharmacist immediately:
- mental or mood changes
- tingling or numbness of hands or feet
- swelling of ankles
- vision problems
- fever or unusual bleeding
Side effects
This medication is usually well tolerated. Nervous system side effects are the most common, including drowsiness, dizziness, unsteadiness when walking, fatigue , and vision changes (double-vision, blurred vision). These side effects appear to be dose-related, and some patients may develop tolerance to these effects after the first several weeks of therapy. If these side effects persist or worsen, a physician should be notified. Other side effects that occur less frequently are irritability, dyspepsia, mood changes, memory loss, difficulty concentrating, slurred speech, and impotence. Elderly patients may be more sensitive to the side effects of gabapentin.
Interactions
One of the advantages of gabapentin is that it is not broken down in the body and does not have a lot of drug interaction. Antacids may interfere with the absorption of this medication in the body; they should be taken at least two hours apart. Gabapentin does not effect other commonly used anticonvulsants (for example, phenytoin, carbamazepine, valproic acid, and phenobarbital).
Olga Bessmertny, Pharm.D.
KEY TERMS
Bipolar disorder
—Recurrent mood disorder equally common among men and women, in which patients have extreme mood alterations between depression and mania or a mix of both. During manic episodes patients may have elevated mood, decreased need for sleep, rapid speech, extreme involvement in pleasurable activities, and may be easily distracted. The drugs commonly used in treatment of bipolar disorder include lithium, carbamazepine, valproic acid, and antidepressants.
Diabetic neuropathy
—A chronic complication of diabetes that can take two forms, peripheral and autonomic. Patients with peripheral neuropathy experience dullness of sensation of pain, temperature, and pressure, especially in lower legs and feet. Autonomic neuropathy can cause alteration in bowel habits, impotence, and decreased heart function. The peripheral type can be treated with medications such as amitriptyline or gabapentin, while the autonomic type is more resistant to treatment.
Multiple sclerosis
—A disorder of central nervous system, causing patches of plaques in brain and spinal cord and usually affecting young adults. Patients may experience visual changes, weakness, numbing or tingling of the hands or feet, changes in bladder and mood patterns.
Postherpetic neuralgia
—Severe stabbing or throbbing pain associated with herpes zoster infection (shingles), resulting from the inflammation of nerve endings where the herpes vesicles erupt.
Trigeminal neuralgia
—Severe, sudden bursts of throbbing and stabbing pain in one of the branches of trigeminal nerve located on the face. The pain can affect any area of the face, teeth, or tongue, and is often caused by some trigger points around the mouth.
Gabapentin
Gabapentin
Recommended dosage
For epilepsy
Definition
Gabapentin is an antiseizure medication. It is sold in the United States under the trade name Neurontin.
Purpose
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.
OTHER
National Library of Medicine. National Institutes of Health. “Gabapentin.” <http://www.nlm.nih.gov/medlineplus/druginfo/uspdi/202732.html>.
Rosalyn Carson-DeWitt, MD
Emily Jane Willingham, PhD
Gabapentin
Gabapentin
Definition
Gabapentin is an anti-seizure medication. It is sold in the United States under the trade name Neurontin.
Purpose
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 United States 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).
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
People over the age of 12 should be started on 300 mg gabapentin taken three times a day. The dose can be increased up to a total of 1,800 mg per day. In some instances, doses of up to 3,600 mg per day have been tolerated.
Children should receive a dosage of 10–15 mg per kg of body weight per day, divided into three equal doses.
Chronic pain may be treated with 300–3,600 mg per day, divided into three equal doses.
When gabapentin is used for bipolar disorder, the starting dose is usually 300 mg taken at bedtime. Depending on the patient's response, the dose can be increased every four to seven days. Many people receive maximum therapeutic benefit at 600 mg per day, although some people have required up to 4,800 mg per day.
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, as this 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, 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. These include more common side effects, such as 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 also check with their doctor immediately: aggressive behavior, irritability, anxiety, difficulty concentrating and paying attention, crying, depression, mood swings, increased emotionality, hyperactivity, 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 hand, 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, MO: Mosby, Incorporated, 1999.
Mosby's Drug Consult. St. Louis, MO: Mosby, Incorporated, 2002.
Rosalyn Carson-DeWitt, M.D.
Gabapentin
Gabapentin
Definition
Gabapentin is a prescription drug that was initially approved to help manage epilepsy . The Food and Drug Administration (FDA) has also approved gabapentin for treatment of the nerve pain that sometimes accompanies herpes infections. Gabapentin is available in the United States under the trade name Neurontin.
Purpose
Although the FDA has only approved gabapentin for managing epilepsy and treating nerve pain associated with herpes infections, doctors often prescribe the medication for managing other conditions, including tremors associated with multiple sclerosis , nerve pain, bipolar disorder, and migraine prevention.
Description
As an antiepileptic drug, gabapentin may be used in conjunction with other drugs to prevent partial seizures . Partial seizures are caused by brief abnormal electrical activity in localized areas of the brain. Partial seizures usually do not cause unconsciousness, but may cause rhythmic contractions in one area of the body or abnormal numbness or tingling sensations.
Although gabapentin was originally approved by the FDA in 1993, it is still not understood how gabapentin prevents seizures. However, the drug is related to gamma-aminobutyric acid (GABA), a neurochemical that possesses inhibitory properties. In brain cells, these inhibitory actions prevent excitatory electrical impulses from spreading to neighboring cells. As a result, gabapentin probably prevents the spread of abnormal excitatory activity in the brain at least in part, by mimicking the actions of GABA.
By preventing excitatory communication between cells, gabapentin may also inhibit the electrical impulses involved in pain conduction. This may account for the drug's ability to alleviate pain, especially nerve pain.
When gabapentin is used along with other therapies for managing epileptic partial seizures, improvements should be observed within 12 weeks. On the other hand, pain relief may be evident within one week when the drug is used for pain associated with herpes infections.
Recommended dosage
For adults, the initial dose of gabapentin is 300 mg taken by mouth three times each day. The dosage may be increased if necessary. Dosages as high as 800–1,200 mg three times daily have been well tolerated.
In children three to 12 years of age, the starting dose should be 10–15 mg/2.2 lb (1 kg)/day given in three equal doses. This dose can be increased until an effective dosage is reached, typically 25–40 mg/2.2 lb (1 kg)/day. Lower dosages are required for patients that have kidney disease.
Precautions
In children, gabapentin may cause behavioral and emotional disorders. The drug should be used cautiously and the dosage should be reduced in those with severe kidney disease. In experimental animals, gabapentin caused tumors to develop; however, it is not known if this occurs in humans.
Patients should take gabapentin only as prescribed. The drug should never be stopped abruptly because doing so increases the likelihood of having a seizure. Since gabapentin can cause dizziness and fatigue , patients should avoid driving or operating complex machinery until they know whether the drug adversely affects their reaction time or impairs their judgment.
Side effects
The most common side effects that cause adults to stop taking gabapentin are dizziness, sleepiness, fatigue, shaky movements, difficulty walking, or swelling in the ankles.
In children, the side effects the drug may cause include emotional problems, hostility, and hyperactivity.
Interactions
Unlike many other drugs that are used to treat epilepsy, there are few drug interactions associated with gabapentin. It is recommended, however, that antacids not be used sooner than two hours after gabapentin to avoid compromising gabapentin's effectiveness.
Resources
BOOKS
Drug Facts and Comparisons, 6th edition. St. Louis, MO: A Wolter Kluwer Company, 2002.
Mosby's Medical Drug Reference. St. Louis, MO: Mosby, Inc, 1999.
Neurontin Package Insert. Vega Baja, PR: Parke-Davis Pharmaceuticals, Ltd., 2002.
Kelly Karpa, PhD, RPh