Important: This page is general information, not medical advice. It does not recommend or prescribe any treatment. Always consult your doctor or pharmacist before starting, stopping or changing any medicine.
Quick facts
- How it is given
- oral
- Type
- human prescription drug
- RxNorm ID
- 310431
We do not publish dosing. How much of this medicine to take, how often, and for how long depends on your age, weight, kidney and liver function, other conditions and other medicines. That is a decision for the person who prescribes or dispenses it. Follow the directions on your own pack and ask your pharmacist if anything is unclear.
What it is used to treat
Gabapentin Capsules, USP are indicated for: Management of postherpetic neuralgia in adults Adjunctive therapy in the treatment of partial onset seizures, with and without secondary generalization, in adults and pediatric patients 3 years and older with epilepsy Gabapentin Capsules, USP are indicated for Postherpetic neuralgia in adults (1) Adjunctive therapy in the treatment of partial onset seizures, with and without secondary generalization, in adults and pediatric patients 3 years and older with epilepsy (1)
About this medicine
The active ingredient in Gabapentin Capsules USP is gabapentin, which has the chemical name 1-(aminomethyl)cyclohexaneacetic acid. The molecular formula of gabapentin is C 9 H 17 NO 2 and the molecular weight is 171.24. The structural formula of gabapentin is: Gabapentin is a white to off-white crystalline solid with a pK a1 of 3.7 and a pK a2 of 10.7. It is freely soluble in water and both basic and acidic aqueous solutions. The log of the partition coefficient (n-octanol/0.05M phosphate buffer) at pH 7.4 is –1.25. Each Gabapentin capsule contains 100 mg, 300 mg, or 400 mg of gabapentin and the following inactive ingredients: Pregelatinized Maize starch, talc, gelatin, titanium dioxide, yellow iron oxide (300 mg and 400 mg only), and red iron oxide (300 mg and 400 mg only), black iron oxide (300 mg and 400 mg only). Ingredients of Imprinting Ink( Black SW-9049) are Black Iron Oxide NF(E 172), Butyl Alcohol NF, Dehydrated Alcohol USP, Isopropyl Alcohol USP, Potassium Hydroxide NF, Propylene Glycol USP, Shellac NF, and Strong Ammonia Solution NF.
How it works
12.1 Mechanism of Action The precise mechanisms by which gabapentin produces its analgesic and antiepileptic actions are unknown. Gabapentin is structurally related to the neurotransmitter gamma-aminobutyric acid (GABA) but has no effect on GABA binding, uptake, or degradation. In vitro studies have shown that gabapentin binds with high-affinity to the α2δ subunit of voltage-activated calcium channels; however, the relationship of this binding to the therapeutic effects of gabapentin is unknown.
Who should not take it
Gabapentin is contraindicated in patients who have demonstrated hypersensitivity to the drug or its ingredients. Known hypersensitivity to gabapentin or its ingredients (4)
Warnings and cautions
Drug Reaction with Eosinophilia and Systemic Symptoms (Multiorgan hypersensitivity): Discontinue if alternative etiology is not be established (5.1) Anaphylaxis and Angioedema: Discontinue and evaluate patient immediately (5.2) Driving impairment; Somnolence/Sedation and Dizziness: Warn patients not to drive until they have gained sufficient experience to assess whether their ability to drive or operate heavy machinery will be impaired (5.3, 5.4) Increased seizure frequency may occur in patients with seizure disorders if Gabapentin is abruptly discontinued (5.5) Suicidal Behavior and Ideation: Monitor for suicidal thoughts / behavior (5.6) Respiratory depression: May occur with gabapentin when used with concomitant central nervous system (CNS) depressants, including opioids, or in the setting of underlying respiratory impairment. Monitor patients and adjust dosage as appropriate ( 5.7 ) Neuropsychiatric Adverse Reactions in Children 3 to 12 Years of Age: Monitor for such events ( 5.8 ) 5.1 Drug Reaction with Eosinophilia and Systemic Symptoms (DRESS)/Multiorgan Hypersensitivity Drug Reaction with Eosinophilia and Systemic Symptoms (DRESS), also known as multiorgan hypersensitivity, has occurred with Gabapentin. Some of these reactions have been fatal or life-threatening. DRESS typically, although not exclusively, presents with fever, rash, and/or lymphadenopathy, in association with other organ system involvement, such as hepatitis, nephritis, hematological abnormalities, myocarditis, or myositis sometimes resembling an acute viral infection. Eosinophilia is often present. This disorder is variable in its expression, and other organ systems not noted here may be involved. It is important to note that early manifestations of hypersensitivity, such as fever or lymphadenopathy, may be present even though rash is not evident. If such signs or symptoms are present, the patient should be evaluated immediately. Gabapentin should be discontinued if an alternative etiology for the signs or symptoms cannot be established. 5.2 Anaphylaxis and Angioedema Gabapentin can cause anaphylaxis and angioedema after the first dose or at any time during treatment. […]
Reported side effects
The following serious adverse reactions are discussed in greater detail in other sections: Drug Reaction with Eosinophilia and Systemic Symptoms (DRESS)/Multiorgan Hypersensitivity [see Warnings and Precautions (5.1) ] Anaphylaxis and Angioedema [see Warnings and Precautions (5.2) ] Somnolence/Sedation and Dizziness [see see Warnings and Precautions (5.4) ] Withdrawal Precipitated Seizure, Status Epilepticus [see see Warnings and Precautions (5.5) ] Suicidal Behavior and Ideation [see see Warnings and Precautions (5.6) ] Respiratory Depression [see Warnings and Precautions (5.7) ] Neuropsychiatric Adverse Reactions (Pediatric Patients 3 to 12 Years of Age) [ see Warnings and Precautions (5.8) ] Sudden and Unexplained Death in Patients with Epilepsy [see Warnings and Precautions (5.10) ] Most common adverse reactions (incidence ≥8% and at least twice that for placebo) were: Postherpetic neuralgia: Dizziness, somnolence, and peripheral edema (6.1) Epilepsy in patients >12 years of age: Somnolence, dizziness, ataxia, fatigue, and nystagmus (6.1) Epilepsy in patients 3 to 12 years of age: Viral infection, fever, nausea and/or vomiting, somnolence, and hostility (6.1) To report SUSPECTED ADVERSE REACTIONS, contact ACI HealthcareUSA, Inc. at 1-888-802-1213 or www.acihealthcareusa.com or FDA at1-800-FDA-1088 or www.fda.gov/medwatch. 6.1 Clinical Trials Experience Because clinical trials are conducted under widely varying conditions, adverse reaction rates observed in the clinical trials of a drug cannot be directly compared to rates in the clinical trials of another drug and may not reflect the rates observed in practice. Postherpetic Neuralgia The most common adverse reactions associated with the use of Gabapentin in adults, not seen at an equivalent frequency among placebo-treated patients, were dizziness, somnolence, and peripheral edema. In the 2 controlled trials in postherpetic neuralgia, 16% of the 336 patients who received Gabapentin and 9% of the 227 patients who received placebo discontinued treatment because of an adverse reaction. […]
Interactions with other medicines
Concentrations increased by morphine; may need dose adjustment (5.4, 7.1 ) 7.1 Opioids Respiratory depression and sedation, sometimes resulting in death, have been reported following coadministration of gabapentin with opioids (e.g., morphine, hydrocodone, oxycodone, buprenorphine) [ see Warnings and Precautions (5.7) ]. Hydrocodone Coadministration of gabapentin with hydrocodone decreases hydrocodone exposure [ see Clinical Pharmacology (12.3) ]. The potential for alteration in hydrocodone exposure and effect should be considered when gabapentin is started or discontinued in a patient taking hydrocodone. Morphine When gabapentin is administered with morphine, patients should be observed for signs of CNS depression, such as somnolence, sedation and respiratory depression [see Clinical Pharmacology (12.3) ]. 7.2 Other Antiepileptic Drugs Gabapentin is not appreciably metabolized nor does it interfere with the metabolism of commonly coadministered antiepileptic drugs [ see Clinical Pharmacology (12.3) ] . 7.3 Maalox ® (aluminum hydroxide, magnesium hydroxide) The mean bioavailability of gabapentin was reduced by about 20% with concomitant use of an antacid (Maalox ® ) containing magnesium and aluminum hydroxides. It is recommended that gabapentin be taken at least 2 hours following Maalox administration [see Clinical Pharmacology (12.3)] . 7.4 Drug/Laboratory Test Interactions Because false positive readings were reported with the Ames N-Multistix SG ® dipstick test for urinary protein when gabapentin was added to other antiepileptic drugs, the more specific sulfosalicylic acid precipitation procedure is recommended to determine the presence of urine protein. 7.1 Opioids Respiratory depression and sedation, sometimes resulting in death, have been reported following coadministration of gabapentin with opioids (e.g., morphine, hydrocodone, oxycodone, buprenorphine) [ see Warnings and Precautions (5.7) ]. Hydrocodone Coadministration of gabapentin with hydrocodone decreases hydrocodone exposure [ see Clinical Pharmacology (12.3) ]. […]
Use in specific groups
Pregnancy: Based on animal data, may cause fetal harm (8.1) 8.1 Pregnancy Pregnancy Exposure Registry There is a pregnancy exposure registry that monitors pregnancy outcomes in women exposed to antiepileptic drugs (AEDs), such as Gabapentin, during pregnancy. Encourage women who are taking Gabapentin during pregnancy to enroll in the North American Antiepileptic Drug (NAAED) Pregnancy Registry by calling the toll free number 1-888-233-2334 or visiting http://www.aedpregnancyregistry.org/. Risk Summary There are no adequate data on the developmental risks associated with the use of Gabapentin in pregnant women. In nonclinical studies in mice, rats, and rabbits, gabapentin was developmentally toxic (increased fetal skeletal and visceral abnormalities, and increased embryofetal mortality) when administered to pregnant animals at doses similar to or lower than those used clinically [see Data]. In the U.S. general population, the estimated background risk of major birth defects and miscarriage in clinically recognized pregnancies is 2 to 4% and 15 to 20%, respectively. The background risk of major birth defects and miscarriage for the indicated population is unknown. Data Animal data When pregnant mice received oral doses of gabapentin (500, 1000, or 3000 mg/kg/day) during the period of organogenesis, embryofetal toxicity (increased incidences of skeletal variations) was observed at the two highest doses. The no-effect dose for embryofetal developmental toxicity in mice (500 mg/kg/day) is less than the maximum recommended human dose (MRHD) of 3600 mg on a body surface area (mg/m 2 ) basis. In studies in which rats received oral doses of gabapentin (500 to 2000 mg/kg/day) during pregnancy, adverse effect on offspring development (increased incidences of hydroureter and/or hydronephrosis) were observed at all doses. The lowest dose tested is similar to the MRHD on a mg/m 2 basis. When pregnant rabbits were treated with gabapentin during the period of organogenesis, an increase in embryofetal mortality was observed at all doses tested (60, 300, or 1500 mg/kg). The lowest dose tested is less than the MRHD on a mg/m 2 basis. […]
If too much is taken
Signs of acute toxicity in animals included ataxia, labored breathing, ptosis, sedation, hypoactivity, or excitation. Acute oral overdoses of gabapentin have been reported. Symptoms have included double vision, tremor, slurred speech, drowsiness, altered mental status, dizziness, lethargy, and diarrhea. Fatal respiratory depression has been reported with gabapentin overdose, alone and in combination with other CNS depressants. Gabapentin can be removed by hemodialysis. If overexposure occurs, call your poison control center at 1-800-222-1222.
Before you take anything new
Tell your pharmacist or doctor about every medicine you take — including ones bought without a prescription, herbal products and supplements. Interactions are one of the most common avoidable causes of harm from medicines, and a pharmacist can check your full list in a couple of minutes.
This page is built from the openFDA record of the U.S. Food and Drug Administration's approved labelling for this product, effective 2 April 2024. Label text has been shortened and reformatted for readability; safety wording has not been altered in meaning. FDA labelling describes products approved in the United States — brand names, strengths, formulations and approved uses may differ in your country. Always read the leaflet that comes with your own pack. PocketsInfo is not affiliated with, and is not endorsed by, the FDA. Retrieved 2026-07-30.