Gabapentin (Generic Neurontin) is an anticonvulsant or antiepileptic drug that is used alongside other medications to control and prevent seizures.
It is also used to help relieve nerve pain a patient experiences following shingles (a painful rash due to herpes zoster infection) in adults.
Gabapentin Prescription Gabapentin is the generic version of Neurontin, and requires a prescription. You can buy generic gabapentin Here.
Gabapentin is a structural analogue of the inhibitory neurotransmitter gamma-aminobutyric acid (GABA) that was first approved for use in the United States in 1993. It was originally developed as a novel anti-epileptic for the treatment of certain types of seizures – today it is also widely used to treat neuropathic pain.
Gabapentin has some stark advantages as compared with other anti-epileptics, such as a relatively benign adverse effect profile, wide therapeutic index, and lack of appreciable metabolism making it unlikely to participate in pharmacokinetic drug interactions. It is structurally and functionally related to another GABA derivative, pregabalin.
In the United States, gabapentin is officially indicated for the treatment of postherpetic neuralgia in adults and for the adjunctive treatment of partial-onset seizures, with or without secondary generalization, in patients 3 years of age and older.
In Europe, gabapentin is indicated for adjunctive therapy in the treatment of partial-onset seizures, with or without secondary generalization, in patients 6 years of age and older and as monotherapy in patients 12 years of age and older. It is also used in adults for the treatment of various types of peripheral neuropathic pain, such as painful diabetic neuropathy.
The action mechanism of gabapentin
The precise mechanism through which gabapentin exerts its therapeutic effects is unclear. The primary mode of action appears to be at the auxillary α2δ-1 subunit of voltage-gated calcium channels (though a low affinity for the α2δ-2 subunit has also been reported).
The major function of these subunits is to facilitate the movement of pore-forming α1 subunits of calcium channels from the endoplasmic reticulum to the cell membrane of pre-synaptic neurons.
There is evidence that chronic pain states can cause an increase in the expression of α2δ subunits and that these changes correlate with hyperalgesia.
Gabapentin appears to inhibit the action of α2δ-1 subunits, thus decreasing the density of pre-synaptic voltage-gated calcium channels and subsequent release of excitatory neurotransmitters.
It is likely that this inhibition is also responsible for the anti-epileptic action of gabapentin.
There is some evidence that gabapentin also acts on adenosine receptors and voltage-gated potassium channels,13 though the clinical relevance of its action at these sites is unclear.
What special precautions should I follow?
Before taking gabapentin,
- tell your doctor and pharmacist if you are allergic to gabapentin, any other medications, or any of the inactive ingredients in the type of gabapentin you plan to take. Ask your pharmacist for a list of the inactive ingredients.
- you should know that gabapentin is available in different forms that may be prescribed for different uses. Ask your doctor to be sure that you are not taking more than one product that contains gabapentin.
- tell your doctor and pharmacist what prescription and nonprescription medications, vitamins, nutritional supplements, and herbal products you are taking or plan to take. Be sure to mention any of the following: hydrocodone (in Hydrocet, in Vicodin, others), medications that make you feel dizzy or drowsy, morphine (Avinza, Kadian, MSIR, others), and naproxen (Aleve, Anaprox, Naprosyn, others). Your doctor may need to change the doses of your medications or monitor you carefully for side effects.
- if you are taking antacids such as Maalox or Mylanta, take them at least 2 hours before you take gabapentin tablets, capsules, or solution.
- tell your doctor if you have or have ever had kidney disease. If you will be taking the extended-release tablets, also tell your doctor if you need to sleep during the day and stay awake at night.
- tell your doctor if you are pregnant, plan to become pregnant, or are breast-feeding. If you become pregnant while taking gabapentin, call your doctor.
- if you are having surgery, including dental surgery, tell the doctor or dentist that you are taking gabapentin.
- you should know that this medication may make you drowsy or dizzy, may slow your thinking, and may cause loss of coordination. Do not drive a car or operate machinery until you know how this medication affects you, and your doctor agrees that it is safe for you to begin these activities.
- if you are giving gabapentin to your child, you should know that your child’s behavior and mental abilities may change while he or she is taking gabapentin. Your child may have sudden changes in mood, become hostile or hyperactive, have difficulty concentrating or paying attention, or be drowsy or clumsy. Have your child avoid activities that could be dangerous, such as riding a bicycle, until you know how gabapentin affects him or her.
- remember that alcohol can add to the drowsiness caused by this medication.
- you should know that your mental health may change in unexpected ways and you may become suicidal (thinking about harming or killing yourself or planning or trying to do so) while you are taking gabapentin for the treatment of epilepsy, mental illness, or other conditions. A small number of adults and children 5 years of age and older (about 1 in 500 people) who took anticonvulsants such as gabapentin to treat various conditions during clinical studies became suicidal during their treatment. Some of these people developed suicidal thoughts and behavior as early as one week after they started taking the medication. There is a risk that you may experience changes in your mental health if you take an anticonvulsant medication such as gabapentin, but there may also be a risk that you will experience changes in your mental health if your condition is not treated. You and your doctor will decide whether the risks of taking an anticonvulsant medication are greater than the risks of not taking the medication. You, your family, or your caregiver should call your doctor right away if you experience any of the following symptoms: panic attacks; agitation or restlessness; new or worsening irritability, anxiety, or depression; acting on dangerous impulses; difficulty falling or staying asleep; aggressive, angry, or violent behavior; mania (frenzied, abnormally excited mood); talking or thinking about wanting to hurt yourself or end your life; withdrawing from friends and family; preoccupation with death and dying; giving away prized possessions; or any other unusual changes in behavior or mood. Be sure that your family or caregiver knows which symptoms may be serious so they can call the doctor if you are unable to seek treatment on your own.
What special dietary instructions should I follow?
Unless your doctor tells you otherwise, continue your normal diet.
What should I do if I forget a dose?
If you forget to take gabapentin capsules, tablets, or oral solution, take the missed dose as soon as you remember it. However, if it is almost time for the next dose or if you forget to take gabapentin extended-release tablets, skip the missed dose and continue your regular dosing schedule. Do not take a double dose to make up for a missed one.
What side effects can this medication cause?
Gabapentin may cause side effects. Tell your doctor if any of these symptoms are severe or do not go away:
- tiredness or weakness
- uncontrollable shaking of a part of your body
- double or blurred vision
- memory problems
- strange or unusual thoughts
- unwanted eye movements
- dry mouth
- increased appetite
- weight gain
- swelling of the hands, feet, ankles, or lower legs
- back or joint pain
- runny nose, sneezing, cough, sore throat, or flu-like symptoms
- ear pain
- red, itchy eyes (sometimes with swelling or discharge)
Some side effects may be serious. If you experience any of the following symptoms, call your doctor immediately:
- swelling of the face, throat, tongue, lips, or eyes
- difficulty swallowing or breathing
Gabapentin may cause other side effects. Call your doctor if you have any unusual problems while taking this medication.
If you experience a serious side effect, you or your doctor may send a report to the Food and Drug Administration’s (FDA) MedWatch Adverse Event Reporting program online [at http://www.fda.gov/Safety/MedWatch] or by phone [1-800-332-1088].
What should I know about storage and disposal of this medication?
Keep this medication in the container it came in, tightly closed, and out of reach of children. Store the tablets, extended-release tablets, and capsules at room temperature, away from excess heat and moisture (not in the bathroom). Store the oral solution in the refrigerator. Throw away any medication that is outdated or no longer needed. Talk to your pharmacist about the proper disposal of your medication.
In case of emergency/overdose
In case of overdose, call your local poison control center at 1-800-222-1222. If the victim has collapsed or is not breathing, call local emergency services at 911.
Symptoms of overdose may include the following:
- double vision
- slurred speech
What other information should I know?
Gabapentin Drug-Drug Interactions
The drug interaction data described in this subsection were obtained from studies involving healthy adults and adult patients with epilepsy:
There is no interaction between Neurontin (gabapentin) and phenytoin, valproic acid, carbamazepine, or phenobarbital. Consequently, Neurontin may be used in combination with other commonly used antiepileptic drugs without concern for alteration of the plasma concentrations of gabapentin or the other antiepileptic drugs.
Co-administration of single doses of gabapentin (125 mg to 500 mg; N= 48) and hydrocodone (10 mg; N= 50) decreased the Cmax and AUC values of hydrocodone in a dose-dependent manner relative to administration of hydrocodone alone. The Cmax and AUC values for hydrocodone were 2% and 4% lower, respectively, after administration of 125 mg gabapentin and 16% and 22% lower, respectively, after administration of 500 mg gabapentin. The mechanism for this interaction is unknown. Hydrocodone increased gabapentin AUC values by 14%. The magnitude of interaction with higher doses of gabapentin is not known.
A literature article reported that when a 60 mg controlled release morphine capsule was administered 2 hours prior to a 600 mg gabapentin capsule in healthy volunteers (N= 12), mean gabapentin AUC increased by 44% compared to gabapentin administered without morphine. Morphine pharmacokinetic parameter values were not affected by administration of gabapentin 2 hours after morphine in this study. Because this was a single dose study, the magnitude of the interaction at steady state and at higher doses of gabapentin are not known.
In healthy adult volunteers (N= 18), the co-administration of single doses of naproxen sodium capsules (250 mg) and gabapentin (125 mg) increased the amount of gabapentin absorbed by 12% to 15%. Gabapentin did not affect naproxen pharmacokinetic parameters in this study. These doses are lower than the therapeutic doses for both drugs. Therefore, the magnitude of interaction at steady state and within the recommended dose ranges of either drug is not known.
Coadministration of gabapentin with the oral contraceptive Norlestrin® does not influence the steady-state pharmacokinetics of norethindrone or ethinyl estradiol.
Coadministration of gabapentin with an aluminum and magnesium-based antacid reduces gabapentin bioavailability by up to 20%. Although the clinical significance of this decrease is not known, co-administration of similar antacids and gabapentin is not recommended.
A slight decrease in renal excretion of gabapentin observed when it is coadministered with cimetidine is not expected to be of clinical importance. The effect of gabapentin on cimetidine has not been evaluated.
Renal excretion of gabapentin is unaltered by probenecid.
Keep all appointments with your doctor.
Before having any laboratory test, tell your doctor and the laboratory personnel that you are taking gabapentin.
If you use a dipstick to test your urine for protein, ask your doctor which product you should use while taking this medication.
Do not let anyone else take your medication. Ask your pharmacist any questions you have about refilling your prescription.
It is important for you to keep a written list of all of the prescription and nonprescription (over-the-counter) medicines you are taking, as well as any products such as vitamins, minerals, or other dietary supplements. You should bring this list with you each time you visit a doctor or if you are admitted to a hospital. It is also important information to carry with you in case of emergencies.
How to use gabapentin
It’s important to read the Medication Guide and, if available, the Patient Information Leaflet provided by your pharmacist, before you begin taking gabapentin and each time you get a refill. If you have any questions, ask your clinician or pharmacist.
Take gabapentin by mouth, either with or without food as directed by your licensed medical professional. Your dosage is based on your medical condition, as well as your response to treatment. In children, the dosage is also based on their weight.
If you are taking the tablet form of gabapentin and your licensed medical professional directs you to split the tablet in half, take the other half-tablet at your next scheduled dose. Be sure to discard remaining half-tablets if you haven’t used them within 28 days of splitting them. If you are taking the capsules, always swallow them whole with plenty of water.
It is very important to follow your licensed medical professional’s dosing instructions exactly. During the first few days taking gabapentin, your licensed medical professional may gradually increase your dose so that your body can adjust to the medication. To minimize the occurrence of side effects, take the very first dose at bedtime.
To get the most benefit, take this medication regularly. Gabapentin will work best when the amount of medication in your body is kept at a constant level. Therefore, take gabapentin at evenly spaced intervals at the same time(s) every day as prescribed. If taking this medication three times per day to control seizures, do not let more than 12 hours pass between doses, or you may increase the risk of having a seizure.
Do not increase your dose or take this medication more frequently without consulting your licensed medical professional. Your risk of serious side effects can increase, and your condition will not improve any faster.
Do not stop taking this medication without consulting your licensed medical professional. Some conditions can become worse when gabapentin is stopped suddenly. If you wish to stop taking gabapentin, your dose may need to be gradually decreased.
Antacids containing aluminum or magnesium may interfere with the absorption of this medication. Therefore, if you are also taking an antacid, it is best to take gabapentin at least 2 hours after taking the antacid.
Different forms of gabapentin (such as immediate-release, sustained-release, enacarbil sustained-release) are absorbed in the body differently. Do not switch from one form to the other without consulting your licensed medical professional.
Tell your licensed medical professional if your condition does not improve or if it worsens.
What are the side effects of gabapentin?
It’s important to be aware of possible side effects before you start taking a medication. Here are the listed side effects for this drug:
Drowsiness, dizziness, loss of coordination, tiredness, blurred/double vision, unusual eye movements, or shaking (tremor) may occur. If any of these effects persist or worsen, tell your doctor or pharmacist promptly.
Remember that your doctor has prescribed this medication because he or she has judged that the benefit to you is greater than the risk of side effects. Many people using this medication do not have serious side effects.
Tell your doctor right away if any of these unlikely but serious side effects occur: swelling of the hands/ankles/feet.
A small number of people who take anticonvulsants for any condition (such as seizures, bipolar disorder, pain) may experience depression, suicidal thoughts/attempts, or other mental/mood problems. Tell your doctor right away if you or your family/caregiver notice any unusual/sudden changes in your mood, thoughts, or behavior including signs of depression, suicidal thoughts/attempts, thoughts about harming yourself.
Get medical help right away if you have any very serious side effects, including: slow/shallow breathing.
A very serious allergic reaction to this drug is rare. However, get medical help right away if you notice any symptoms of a serious allergic reaction, including: fever, swollen lymph nodes, rash, itching/swelling (especially of the face/tongue/throat), severe dizziness, trouble breathing.
This is not a complete list of possible side effects. If you notice other effects not listed above, contact your doctor or pharmacist.
In the US – Call your doctor for medical advice about side effects. You may report side effects to FDA at 1-800-FDA-1088 or at www.fda.gov/medwatch.
Warnings and precautions for gabapentin
It’s also important to be aware of precautions and warnings around taking this medication.
Before taking gabapentin, tell your doctor or pharmacist if you are allergic to it; or to gabapentin enacarbil; or if you have any other allergies. This product may contain inactive ingredients, which can cause allergic reactions or other problems. Talk to your pharmacist for more details.
Before using this medication, tell your doctor or pharmacist your medical history, especially of: kidney disease, mental/mood problems (such as depression, thoughts of suicide), use/abuse of drugs/alcohol, breathing problems.
This drug may make you dizzy or drowsy or blur your vision. Alcohol or marijuana (cannabis) can make you more dizzy or drowsy. Do not drive, use machinery, or do anything that needs alertness or clear vision until you can do it safely. Limit alcoholic beverages. Talk to your doctor if you are using marijuana (cannabis).
Before having surgery, tell your doctor or dentist about all the products you use (including prescription drugs, nonprescription drugs, and herbal products).
Older adults may be more sensitive to the side effects of this drug, especially swelling of the hands/ankles/feet, slow/shallow breathing, dizziness, or loss of coordination. Dizziness and loss of coordination can increase the risk of falling.
Children may be more sensitive to the side effects of this drug, especially mental/mood/behavior changes (such as hostility, problems concentrating, restlessness).
During pregnancy, this medication should be used only when clearly needed. Discuss the risks and benefits with your doctor.
Gabapentin passes into breast milk. Consult your doctor before breast-feeding.
Pill storage for gabapentin
Store your gabapentin at room temperature, and away from moisture and light. Do not store gabapentin in the bathroom. Keep gabapentin, and all medications, away from pets and children.
Do not flush this or any medications down the toilet or pour them into a drain unless instructed to do so. When you no longer need your gabapentin, or when it has expired, be sure to properly discard the remaining product. Your pharmacist or local waste disposal company can tell you how.
Drug interactions for gabapentin
Drug interactions can change how gabapentin and your other medications work, or even increase your risk for serious side effects. This document does not contain all possible drug interactions. Be sure to keep a list of all the products you use (including prescription and nonprescription drugs, as well as herbal products) and share it with your clinician and pharmacist. Do not start, stop, or change the dosage of any medicines without your licensed medical professional’s approval.
A product that may interact with gabapentin: orlistat.
Tell your clinician or pharmacist if you use other products that cause drowsiness, like drugs for sleep or anxiety (such as alprazolam, lorazepam, zolpidem), opioid pain or cough relievers (such as codeine, hydrocodone), antihistamines (such as cetirizine, diphenhydramine), muscle relaxants (such as carisoprodol, cyclobenzaprine), alcohol or marijuana (cannabis).
Be sure to also check the labels on all of your medications (including cough-and-cold or allergy products) because they may contain ingredients that cause drowsiness. Ask your pharmacist about using those medications safely.
Do not use this medication with other medications that contain gabapentin (including gabapentin enacarbil).
Gabapentin may interfere with certain laboratory tests for urine protein. Make sure laboratory personnel and all your licensed medical professionals know you use this drug.
Symptoms of gabapentin overdose may include: severe drowsiness, slurred speech, weakness. If someone has overdosed and has serious symptoms such as passing out or trouble breathing, call 911. Otherwise, call a poison control center immediately. US residents can call their local poison control center at 1-800-222-1222. Canada residents can call a provincial poison control center.