Note: Do not exceed 12 hours between doses with 3 times daily dosing. Pediatric doses presented as mg/kg/day and mg/kg/dose; use precaution.
Seizures, partial onset; adjunctive therapy: Oral: Immediate release: Note: If gabapentin is discontinued or if another antiseizure medication is added to therapy, it should be done slowly over a minimum of 1 week.
Children 3 to <12 years:
Initial: 10 to 15 mg/kg/day divided into 3 doses daily; titrate dose upward over ~3 days
Maintenance usual dose:
Children 3 to 4 years: 40 mg/kg/day divided into 3 doses daily; maximum daily dose: In one long-term study, doses up to 50 mg/kg/day were well-tolerated
Children 5 to <12 years: 25 to 35 mg/kg/day divided into 3 doses daily; maximum daily dose: In one long-term study, doses up to 50 mg/kg/day were well-tolerated
Children ≥12 years and Adolescents: Initial: 300 mg 3 times daily; titrate dose upward if needed; usual maintenance dose: 900 to 1,800 mg/day divided into 3 doses daily; doses up to 2,400 mg/day divided into 3 doses daily are well tolerated long-term; maximum daily dose: Doses up to 3,600 mg/day have been tolerated in short-term studies.
Neuropathic pain: Limited data available: Oral: Immediate release: Children and Adolescents: Initial: 5 mg/kg/dose up to 300 mg at bedtime; day 2: Increase to 5 mg/kg/dose twice daily (up to 300 mg twice daily); day 3: Increase to 5 mg/kg/dose 3 times daily (up to 300 mg 3 times daily); further titrate with dosage increases (not frequency) to effect; American Pain Society (APS) recommends a lower initial dose of 2 mg/kg/day which may be considered if concurrent analgesics are also sedating; usual dosage range: 8 to 35 mg/kg/day divided into 3 doses daily (APS, 2008; Galloway, 2000); maximum daily dose: 3,600 mg/day
Dosage adjustment for concomitant therapy: Significant drug interactions exist, requiring dose/frequency adjustment or avoidance. Consult drug interactions database for more information.
Immediate release:
Children <12 years: There are no dosing adjustments provided in the manufacturer’s labeling (has not been studied).
Children ≥12 years and Adolescents: See table.
Creatinine Clearance (mL/minute) |
Total Daily Dose Range (mg/day) |
Dosage Regimens (Maintenance Doses) (mg) | ||||
---|---|---|---|---|---|---|
ACrCl <15 mL/minute: Reduce daily dose in proportion to creatinine clearance. | ||||||
BSupplemental dose should be administered after each 4 hours of hemodialysis (patients on hemodialysis should also receive maintenance doses based on renal function as listed in the upper portion of the table). | ||||||
≥60 |
900 to 3,600 |
300 3 times/day |
400 3 times/day |
600 3 times/day |
800 3 times/day |
1,200 3 times/day |
>30 to 59 |
400 to 1,400 |
200 twice daily |
300 twice daily |
400 twice daily |
500 twice daily |
700 twice daily |
>15 to 29 |
200 to 700 |
200 daily |
300 daily |
400 daily |
500 daily |
700 daily |
15A |
100 to 300 |
100 daily |
125 daily |
150 daily |
200 daily |
300 daily |
HemodialysisB |
Posthemodialysis Supplemental Dose | |||||
125 mg |
150 mg |
200 mg |
250 mg |
350 mg |
There are no dosage adjustments provided in the manufacturer’s labeling; however, adjustment not necessary since gabapentin is not hepatically metabolized.
(For additional information see "Gabapentin: Drug information")
Note: For patients with respiratory disease, initiate therapy at the lowest dose (FDA 2019).
Alcohol use disorder, moderate to severe (alternative agent) (off-label use): Immediate release: Oral: Initial: 300 mg once daily; increase dose based on response and tolerability in increments of 300 mg every 1 to 2 days up to a target dose of 600 mg 3 times daily (Brower 2008; Mason 2014; VA/DoD 2015). Note: Gabapentin is suggested by some experts as an alternative when first-line agents cannot be used (Johnson 2019; VA/DoD 2015). Gabapentin may be misused by some patients with substance use disorders; evaluate for risk and signs of addiction and dependence (Mersfelder 2016).
Alcohol withdrawal (alternative agent) (off-label use):
Note: Withdrawal will progress at different rates in some patients; flexibility in dosing and duration is warranted (Holt 2018; VA/DoD 2015). The following is one suggested regimen based on a single randomized, double-blind trial:
Immediate release: Oral: Initial: 300 to 400 mg 3 times daily on days 1 through 3, then 300 to 400 mg twice daily on day 4, then discontinue. For breakthrough symptoms during days 1 through 4, consider providing single doses of 100 mg, which may be administered up to 3 times daily, and a 300 mg dose reserved for the evening (Myrick 2009).
Cough, chronic refractory (alternative agent) (off-label use): Immediate release: Oral: Initial: 300 mg once daily; increase dose gradually based on response and tolerability in increments of 300 mg to a maximum dose of 900 mg twice daily (ACCP [Gibson 2016]; Ryan 2012). Re-evaluate therapeutic need after 6 months (ACCP [Gibson 2016]).
Fibromyalgia (alternative agent) (off-label use):
Note: For patients who do not respond to or tolerate preferred agents (Goldenberg 2020):
Immediate release: Oral: Initial: 100 to 300 mg once daily at bedtime; increase dose gradually based on response and tolerability every 1 to 2 weeks to a target dose of 1.2 to 2.4 g/day in divided doses (Arnold 2007; Goldenberg 2020).
Generalized anxiety disorder (alternative agent) (off-label use):
Note: Adjunctive therapy for short-term symptom relief until concurrent therapy is effective (eg, 4 to 6 weeks, followed by tapering). Long-term augmentation may be considered when preferred treatments (eg, serotonin reuptake inhibitors) are partially effective (Craske 2021).
Immediate release: Oral: Initial: 300 mg/day; may increase dose every ≥3 days based on response and tolerability up to 2.4 g/day, in 2 to 3 divided doses (Craske 2021; Garakani 2020; Lavigne 2012). Note: In patients sensitive to side effects, some experts suggest a lower starting dose of 100 mg/day and more gradual titration (Craske 2021).
Hiccups (singultus) (off-label use ): Immediate release: Oral: Usual dose range: 300 mg to 1.2 g/day in 3 to 4 divided doses (Hernández 2004; Jatzko 2007; Moretti 2004; Porzio 2010; Schuchmann 2007). Can be discontinued the day after hiccups subside; long-term therapy may be warranted for persistent or relapsing hiccups (eg, palliative care) (Lembo 2020). Note: In patients with refractory hiccups, may use in combination with a proton pump inhibitor, baclofen, or metoclopramide (Kohse 2017).
Neuropathic pain:
General dosing recommendations (for other than postherpetic neuralgia) (off-label use):
Note: For chronic use, an adequate trial with gabapentin may require 2 months or more (Bone 2002; Tauben 2020). For critically ill patients with neuropathic pain, gabapentin may be a useful component of multimodal pain control (SCCM [Devlin 2018]).
Immediate release: Oral: Initial: 100 to 300 mg 1 to 3 times daily (ADA [Pop-Busui 2017]; Dolgun 2014; Mishra 2012); increase dose based on response and tolerability to a target dose range of 300 mg to 1.2 g 3 times daily (AAN [Bril 2011]; ADA [Pop-Busui 2017]; EFNS [Attal 2010]; IASP [Finnerup 2015]).
Extended release: Oral: Initial: 300 mg at bedtime; increase dose based on response and tolerability to a target dose of 900 mg to 3.6 g once daily (IASP [Finnerup 2015]; Sandercock 2012).
Postherpetic neuralgia:
Immediate release: Oral: 300 mg once on day 1,300 mg twice daily on day 2, and 300 mg 3 times daily on day 3, then increase as needed up to 1.8 to 3.6 g/day in divided doses. Additional benefit of doses >1.8 g/day has not been established.
Extended release: Oral: Initial: 300 mg once daily; increase by 300 mg each day up to 900 mg once daily. Further increase as needed up to 1.8 g once daily. Additional benefit of doses >1.8 g/day has not been established.
Pruritus, chronic (alternative agent) (off-label use):
Note: For patients with pruritus resistant to preferred therapies (Matsuda 2016; Weisshaar 2012):
Neuropathic (eg, brachioradial pruritus, notalgia paresthetica) or malignancy-related pruritus: Immediate release: Oral: Initial: 300 mg/day in 1 to 3 divided doses; increase dose based on response and tolerability up to 1.8 g/day in divided doses (Kanitakis 2006; Winhoven 2004; Yilmaz 2010). Higher doses up to 3.6 g/day have been used in oncology populations (Demierre 2006; Lee 2010).
Uremic pruritus: Immediate release: Oral: Initial: 100 mg after dialysis on hemodialysis days; may increase dose based on response and tolerability up to 300 mg after dialysis on hemodialysis days (Gunal 2004; Kobrin 2021; Nofal 2016; Razeghi 2009).
Restless legs syndrome (off-label use): Immediate release: Oral: Initial: 100 to 300 mg once daily 2 hours before bedtime; may increase dose every 1 to 2 weeks until symptom relief is achieved (range: 300 mg to 2.4 g/day). Suggested maintenance dosing schedule for doses ≥600 mg/day: One-third of total daily dose given midday, remaining two-thirds of the total daily dose given in the evening (Garcia-Borreguero 2002; Happe 2003; IRLSSG/EURLSSG/RLS-F [Garcia-Borreguero 2016]; Saletu 2010; Silber 2021; Vignatelli 2006).
Seizures, focal (partial) onset: Immediate release: Oral: Initial: 300 mg 3 times daily; increase dose based on response and tolerability. Usual dosage: 300 to 600 mg 3 times daily; doses up to 2.4 g/day and 3.6 g/day have been tolerated in long-term and short-term clinical studies, respectively. Some experts recommend a lower starting dose (eg, 100 mg 3 times daily) with titration as tolerated (Schachter 2018).
Social anxiety disorder (alternative agent) (off-label use):
Note: Monotherapy or adjunctive therapy for patients who do not tolerate or respond to preferred agents (Stein 2020):
Immediate release: Oral: Initial: 300 mg twice daily; increase dose based on response and tolerability in increments of no more than 300 mg/day up to a maximum of 3.6 g/day in 3 divided doses (Pande 1999). Some experts recommend initiating with 100 mg 3 times daily in patients with respiratory disease (Stein 2020).
Vasomotor symptoms associated with menopause (off-label use):
Immediate release: Oral: Initial: 300 to 400 mg once daily at bedtime; some experts use an initial dose of 100 mg once daily to avoid adverse effects (Santen 2018); increase gradually (eg, over 3 to 12 days) based on response and tolerability up to 600 mg to 2.4 g/day in 2 to 3 divided doses (ACOG 2014; NAMS 2015; Reddy 2006; Toulis 2009). Some experts suggest gabapentin for women whose symptoms occur primarily at night and favor a maximum dose of 900 mg to 1.2 g, given as one dose at bedtime (ES [Stuenkel 2015]; Santen 2018).
Extended release: Oral: Initial: 600 mg once daily at bedtime; increase gradually (eg, 600 mg every 3 days) to target dose of 600 mg in the morning and 1.2 g at bedtime (Pinkerton 2014).
Discontinuation of therapy: In patients receiving gabapentin chronically, unless safety concerns require a more rapid withdrawal, gabapentin should be withdrawn gradually over ≥1 week to minimize the potential of increased seizure frequency (in patients with epilepsy) or other withdrawal symptoms (eg, confusion, irritability, tachycardia, diaphoresis) (Norton 2001; Tran 2005).
Dosage adjustment for concomitant therapy: Significant drug interactions exist, requiring dose/frequency adjustment or avoidance. Consult drug interactions database for more information.
The renal dosing recommendations are based upon the best available evidence and clinical expertise. Senior Editorial Team: Bruce Mueller, PharmD, FCCP, FASN, FNKF; Jason Roberts, PhD, BPharm (Hons), B App Sc, FSHP, FISAC; Michael Heung, MD, MS.
Oral: Immediate release:
Note: Initial doses of gabapentin should be conservative and titrated based on effectiveness and tolerability.
CrCl (mL/minute)c |
Approximate Maintenance Dose Adjustment |
Maximum Maintenance Dose |
---|---|---|
aChoose normal dose based on indication (see Adult dosing), then choose the adjusted dose from the column corresponding to the patient's CrCl. | ||
bExpert opinion derived from Blum 1994, Davison 2014, Davison 2019, manufacturer's labeling. | ||
cEstimation of renal function for dosing adjustments should be done using the Cockcroft Gault formula. | ||
>79 |
No dose adjustment necessary |
3,600 mg/day in 3 divided doses |
50 to 79 |
No dose adjustment necessary |
1,800 mg/day in 3 divided doses |
30 to 49 |
~50% reduction |
900 mg/day in 2 to 3 divided doses |
15 to 29 |
~75% reduction |
600 mg/day in 1 to 2 divided doses |
<15 |
~90% reduction |
300 mg/day in 1 dose |
Hemodialysis, intermittent (thrice weekly): Dialyzable (50% over 4 hours [Wong 1995]):
Initial: 100 mg 3 times per week after hemodialysis. Titrate to effect up to 300 mg 3 times per week given after hemodialysis on dialysis days (Atalay 2013; Gunal 2004; Kobrin 2018; Koncicki 2015; Nofal 2016; Razeghi 2009; Spaia 2009).
Note: Some experts recommend cautious titration to a maximum of 300 mg/day in select patients requiring additional pain control (Koncicki 2017; Kurella 2003; Davison 2019).
Peritoneal dialysis:
Initial: 100 mg every other day. Titrate to effect up to 300 mg every other day (Koncicki 2015; expert opinion).
Note: Some experts recommend cautious titration to a maximum of 300 mg/day in select patients requiring additional pain control (Koncicki 2017; Kurella 2003; Davison 2019).
CRRT:
Note: Drug clearance is dependent on the effluent flow rate, filter type, and method of renal replacement. Recommendations are based on high-flux dialyzers and effluent flow rates of 20 to 25 mL/kg/hour (or approximately 1,500 to 3,000 mL/hour) unless otherwise noted.
CVVH/CVVHD/CVVHDF:
Note: Dosing based on expert opinion; no evidence available. Pharmacokinetic characteristics and one case report suggest gabapentin is cleared by CRRT (Guddati 2012).
Initial: 100 mg twice daily and titrate to effect. Suggested maximum dose: 300 mg twice daily.
Oral: Extended release:
Note: Follow initial dose titration schedule if treatment naive. Estimation of renal function for dosing adjustments should be done using the Cockcroft-Gault formula. Renally adjusted dose recommendations are based on doses up to 1.8 g/day.
CrCl ≥60 mL/minute: Oral: No dosage adjustment necessary.
CrCl >30 to 59 mL/minute: Oral: 600 mg to 1.8 g once daily; dependent on tolerability and clinical response.
CrCl <30 mL/minute: Use is not recommended.
End-stage renal disease requiring hemodialysis: Use is not recommended.
Peritoneal dialysis: Use is not recommended.
There are no dosage adjustments provided in the manufacturer's labeling; however, gabapentin is not hepatically metabolized.
Excipient information presented when available (limited, particularly for generics); consult specific product labeling.
Capsule, Oral:
Neurontin: 100 mg, 300 mg, 400 mg
Generic: 100 mg, 300 mg, 400 mg
Solution, Oral:
Neurontin: 250 mg/5 mL (470 mL) [strawberry anise flavor]
Generic: 250 mg/5 mL (473 mL); 250 mg/5 mL (5 mL, 6 mL, 470 mL)
Tablet, Oral:
Neurontin: 600 mg, 800 mg [scored]
Generic: 600 mg, 800 mg
Tablet, Oral, Extended Release:
Gralise: 300 mg [contains soybean lecithin]
Gralise: 600 mg
Yes
Excipient information presented when available (limited, particularly for generics); consult specific product labeling.
Capsule, Oral:
Neurontin: 100 mg, 300 mg, 400 mg [contains corn starch, fd&c blue #2 (indigotine)]
Generic: 100 mg, 300 mg, 400 mg
Tablet, Oral:
Neurontin: 600 mg, 800 mg [contains corn starch]
Generic: 600 mg, 800 mg
An FDA-approved patient medication guide, which is available with the product information and as follows, must be dispensed with this medication:
Immediate release: Capsule, tablet, oral solution: May consider administration of first dose on first day at bedtime to avoid somnolence and dizziness. May be administered without regard to meals; administration with meals may decrease adverse GI effects. Dose may be administered as combination of dosage forms; do not administer within 2 hours of magnesium- or aluminum-containing antacids. When given 3 times daily, the maximum time between doses should not exceed 12 hours. Capsule should be administered with plenty of water to ensure complete swallowing. Although the manufacturer recommends swallowing capsules whole, some centers have opened the capsules and mixed the contents in drinks (eg, orange juice) or food (eg, applesauce) when necessary (Gidal 1998; Khurana 1996). The 600 mg and 800 mg tablets are scored and may be split if a half-tablet is needed; manufacturer recommends that half tablets not used within 28 days of breaking the scored tablets should be discarded.
Oral:
Immediate release: May administer without regards to meals. Administer first dose on first day at bedtime to avoid somnolence and dizziness. Dosage must be adjusted for renal function; when given 3 times daily, the maximum time between doses should not exceed 12 hours. Capsules may be opened and sprinkled on food (eg, applesauce, orange juice, pudding) for patients unable to swallow capsules (Gidal 1998).
Extended release: Administer with evening meal. Swallow whole; do not chew, crush, or split.
Capsules and tablets: Store at 25°C (77°F); excursions permitted to 15°C to 30°C (59°F to 86°F). Use scored 600 or 800 mg tablets that are broken in half within 28 days of breaking the tablet.
Oral solution: Store refrigerated at 2°C to 8°C (36°F to 46°F).
Adjunct for treatment of partial seizures with or without secondary generalized seizures (Neurontin: FDA approved in ages ≥3 years and adults); management of post-herpetic neuralgia (Gralise, Neurontin: FDA approved in adults); has also been used as adjunct in the treatment of neuropathic pain
Gabapentin may be confused with gabapentin enacarbil, gemfibrozil
Neurontin may be confused with Motrin, Neoral, nitrofurantoin, Noroxin [DSC], Zarontin
The Institute for Safe Medication Practices (ISMP) includes this medication (when used for neuropathic pain) among its list of drugs that have a heightened risk of causing significant patient harm when used in error.
Gabapentin may cause dose-dependent CNS depression and present as dizziness and/or drowsiness. In addition, serious, life-threatening, and fatal respiratory depression may occur; most cases occur with concomitant use of CNS depressants (especially opioids) in the setting of underlying respiratory impairment or in older patients (Ref). CNS depression may impair physical or mental abilities and result in accidental injury, including falls.
Mechanism: Dose-related; related to pharmacologic action (ie, structurally related to GABA)
Onset: Varied; timing impacted by concomitant use of medications known to cause CNS depression (eg, opioids) (Ref)
Risk factors:
• Concomitant use of alcohol or other CNS depressants (eg, opioids, benzodiazepines, antidepressants, antihistamines) (Ref)
• Patients with underlying respiratory impairment (Ref)
• Older patients (Ref)
Anaphylaxis or angioedema may occur. Signs and symptoms may include dyspnea, swelling of the lips, throat, and tongue, and hypotension (manufacturer’s labeling).
Mechanism: Non-dose-related; immunologic. In general, anaphylaxis is an IgE-mediated reaction (Ref).
Onset: Rapid; most anaphylactic reactions occur within minutes to hours of administration (Ref).
Risk factors:
• Prior history of immediate hypersensitivity reaction to gabapentin. Note: It is unknown whether cross-reactivity exists between gabapentin and pregabalin, given their similar structures. If an agent with similar structure is prescribed in a patient with a documented allergy to this drug, the possibility of cross-reactivity should be considered.
Isolated cases of dermatologic reactions, including maculopapular skin rash, drug reaction with eosinophilia and systemic symptoms (DRESS), Stevens-Johnson syndrome, toxic epidermal necrolysis, bullous pemphigoid, erythema multiforme, and hypersensitivity angiitis have been reported (Ref).
Mechanism: Non-dose-related; immunologic; Delayed hypersensitivity reactions are mediated by T-cells or antibodies other than IgE (eg, IgG-mediated, such as some cytopenias) (Ref). Severe cutaneous adverse reactions (SCARs) are delayed type IV hypersensitivity reactions involving a T-cell mediated drug-specific immune response (Ref).
Onset: Varied; type IV reactions are delayed hypersensitivity reactions that typically occur days to weeks after drug exposure, but may occur more rapidly (usually within 1 to 4 days) upon reexposure (Ref).
Risk factors:
• Prior history of delayed hypersensitivity reaction to gabapentin. Note: It is unknown whether cross-reactivity exists between gabapentin and pregabalin, given their similar structures. If an agent with similar structure is prescribed in a patient with a documented allergy to this drug, the possibility of cross-reactivity should be considered. Of note, Gabapentin is usually considered a safe agent for patients with a previous history of drug allergies to other antiseizure medications (Ref).
Neuropsychiatric adverse reactions have occurred in pediatric patients (ages 3 to 12 years) with epilepsy, including emotional lability; hostility (eg, aggressive behaviors); changes in behavior and thinking (eg, concentration problems, changes in school performance); and hyperkinetic muscle activity (eg, restlessness, hyperactivity). In addition, agitation has been reported following use for neuropathic pain in adult patients with cognitive impairment secondary to brain injury (Ref).
Mechanism: Non-dose-related; exact mechanism not established; one theory is gabapentin results in disinhibition similar to what is seen following benzodiazepine use (Ref).
Risk factors:
• Children with intellectual disabilities and attention-deficit/hyperactivity disorders (Ref).
Pooled analysis of trials involving various antiseizure medications (regardless of indication) showed an increased risk of suicidal ideation and suicidal tendencies.
Mechanism: Non-dose-related. Exact mechanism not established; one theory is antiseizure medications lower the threshold for manifesting psychiatric symptoms in patients susceptible to psychiatric disorders or antiseizure-induced disinhibition and impulsiveness, thereby influencing and promoting suicidal acts (Ref).
Onset: As early as 1 week after initiation of antiseizure drugs, including gabapentin
Risk factors:
• Preexisting risk factors for suicidal thoughts and behaviors (including epilepsy)
• Prior history of psychiatric disorders or aggressive behaviors (Ref)
The following adverse drug reactions and incidences are derived from product labeling unless otherwise specified. [IR = Immediate Release, ER = Extended Release]
>10%:
Infection: Viral infection (IR, children: 11%)
Nervous system: Ataxia (IR, adolescents and adults: 1% to 13%), dizziness (IR, adolescents and adults: 17% to 28%; ER, adults: 11%; IR, children: 3%) (table 1) , drowsiness (IR, adolescents and adults: 19% to 21%; IR, children: 8%; ER, adults: 5%) (table 2) , fatigue (IR, adolescents and adults: 11%; IR, children: 3%)
Drug (Gabapentin) |
Placebo |
Population |
Dosage Form |
Indication |
Number of Patients (Gabapentin) |
Number of Patients (Placebo) |
---|---|---|---|---|---|---|
3% |
2% |
Children |
IR |
Epilepsy |
119 |
128 |
17% |
7% |
Adolescents & adults |
IR |
Epilepsy |
543 |
378 |
28% |
8% |
Adults |
IR |
Postherpetic neuralgia |
336 |
227 |
11% |
2% |
Adults |
ER |
Postherpetic neuralgia |
359 |
364 |
Drug (Gabapentin) |
Placebo |
Population |
Dosage Form |
Indication |
Number of Patients (Gabapentin) |
Number of Patients (Placebo) |
---|---|---|---|---|---|---|
8% |
5% |
Children |
IR |
Epilepsy |
119 |
128 |
19% |
9% |
Adolescents & adults |
IR |
Epilepsy |
543 |
378 |
21% |
5% |
Adults |
IR |
Postherpetic neuralgia |
336 |
227 |
5% |
3% |
Adults |
ER |
Postherpetic neuralgia |
359 |
364 |
1% to 10%:
Cardiovascular: Hypertension (ER, adults: >1%), peripheral edema (adolescents and adults: 2% to 8%), vasodilation (IR, adolescents and adults: 1%)
Dermatologic: Excoriation of skin (IR, adolescents and adults: 1%), skin rash (ER, adults: >1%)
Endocrine & metabolic: Hyperglycemia (IR, adults: 1%), weight gain (2% to 3%)
Gastrointestinal: Constipation (adolescents and adults: 1% to 4%), dental disease (IR, adolescents and adults: 2%), diarrhea (IR, adults: 6%), dyspepsia (adolescents and adults: 1% to 2%), nausea (IR: ≤8%; ER, adults: >1%), viral gastroenteritis (ER, adults: >1%), vomiting (IR: ≤8%), xerostomia (adolescents and adults: ≤5%)
Genitourinary: Impotence (IR, adolescents and adults: 2%), urinary tract infection (ER, adults: 2%)
Infection: Herpes zoster infection (ER, adults: >1%), infection (IR, adults: 5%)
Nervous system: Abnormal gait (IR, adults: 2%), abnormality in thinking (IR, adolescents and adults: 2% to 3%) (table 3) , amnesia (IR, adolescents and adults: 2%), confusion (ER, adults: >1%), depression (IR, adolescents and adults: 2%), dysarthria (IR, adolescents and adults: 2%), emotional lability (IR, children: 4% to 6%) (table 4) , hostility (IR, children: 5% to 8%) (table 5) , lethargy (ER, adults: 1%), memory impairment (ER, adults: >1%), pain (ER, adults: 1%), status epilepticus (IR, adolescents and adults: 2%), vertigo (ER, adults: 1%)
Drug (Gabapentin) |
Placebo |
Population |
Dosage Form |
Indication |
Number of Patients (Gabapentin) |
Number of Patients (Placebo) |
---|---|---|---|---|---|---|
2% |
1% |
Adolescents & adults |
IR |
Epilepsy |
543 |
378 |
3% |
0% |
Adults |
IR |
Postherpetic neuralgia |
336 |
227 |
Drug (Gabapentin) |
Placebo |
Population |
Dosage Form |
Indication |
Number of Patients (Gabapentin) |
Number of Patients (Placebo) |
---|---|---|---|---|---|---|
6% |
1% |
Children |
IR |
Epilepsy |
N/A |
N/A |
4% |
2% |
Children |
IR |
Epilepsy |
119 |
128 |
Drug (Gabapentin) |
Placebo |
Population |
Dosage Form |
Indication |
Number of Patients (Gabapentin) |
Number of Patients (Placebo) |
---|---|---|---|---|---|---|
8% |
2% |
Children |
IR |
Epilepsy |
119 |
128 |
5% |
1% |
Children |
IR |
Epilepsy |
N/A |
N/A |
Neuromuscular & skeletal: Asthenia (IR, adults: 6%), back pain (adolescents and adults: 2%), hyperkinetic muscle activity (IR, children: 3% to 5%) (table 6) , joint swelling (ER, adults: >1%), limb pain (ER, adults: 2%), tremor (IR, adolescents and adults: 7%)
Drug (Gabapentin) |
Placebo |
Population |
Dosage Form |
Indication |
Number of Patients (Gabapentin) |
Number of Patients (Placebo) |
---|---|---|---|---|---|---|
5% |
3% |
Children |
IR |
Epilepsy |
N/A |
N/A |
3% |
1% |
Children |
IR |
Epilepsy |
119 |
128 |
Ophthalmic: Amblyopia (IR: 3% to 4%), conjunctivitis (IR, adults: 1%), diplopia (IR, adolescents and adults: 1% to 6%), nystagmus disorder (IR, adolescents and adults: 8%)
Otic: Otitis media (IR, adults: 1%)
Respiratory: Bronchitis (IR, children: 3%), cough (IR, adolescents and adults: 2%), dry throat (IR, adolescents and adults: ≤2%), nasopharyngitis (ER, adults: 3%), pharyngitis (IR, adolescents and adults: 1% to 3%), pneumonia (ER, adults: >1%), respiratory tract infection (IR, children: 3%), upper respiratory tract infection (ER, adults: >1%)
Miscellaneous: Accidental injury (IR, adults: 3%), fever (IR, children: 10%; ER, adults: >1%) (table 7)
Drug (Gabapentin) |
Placebo |
Population |
Dosage Form |
Indication |
Number of Patients (Gabapentin) |
Number of Patients (Placebo) |
---|---|---|---|---|---|---|
3% |
1% |
Adults |
IR |
Postherpetic neuralgia |
336 |
227 |
<1%:
Hypersensitivity: Anaphylaxis, angioedema
Immunologic: Drug reaction with eosinophilia and systemic symptoms (Ragucci 2001; Scaparotta 2011)
Nervous system: Suicidal ideation (Molero 2019), suicidal tendencies (Molero 2019)
Postmarketing:
Cardiovascular: Cardiomyopathy (Tellor 2019), hypersensitivity angiitis (rare: <1%) (Sahin 2008)
Dermatologic: Bullous pemphigoid (rare: <1%) (Flamm 2017), dermatitis (interstitial granulomatous) (Georgesen 2014), erythema multiforme, Stevens-Johnson syndrome (rare: <1%) (De Toledo 1999; Frey 2017), toxic epidermal necrolysis (rare: <1%) (Oskay 2006; Ragucci 2001)
Endocrine & metabolic: Altered serum glucose, amenorrhea (Berger 2004), change in libido, hypoglycemia (Penumalee 2003; Scholl 2015), hyponatremia (Falhammar 2018; Lu 2017; Wilton 2002), thyroiditis (Fyre 1999)
Genitourinary: Breast hypertrophy (Zylicz 2000), ejaculation failure (Labbate 1999), ejaculatory disorder, urinary incontinence (Rissardo 2019)
Hematologic & oncologic: Thrombocytopenia (Ataki 2015)
Hepatic: Hepatotoxicity (Jackson 2018), increased liver enzymes (Jackson 2018; Lasso-de-la-Vega 2001)
Infection: Parasitic infection (Lopez 2010)
Nervous system: Agitation (Childers 1997), anorgasmia (Labbate 1999), coma (Abdennour 2017; Butler 2003; Dogukan 2006), encephalopathy (Beauvais 2015), movement disorder (Allford 2007; Attupurath 2009; Palomeras 2000; Pina 2005; Raju 2007; Rohman 2014; Souzdalnitski 2014; Twardowschy 2008; Zesiewicz 2008), myoclonus (facial) (Hampton 2019; Hui 2019; Yeddi 2019), polyneuropathy (Gould 1998), stuttering (Nissani 1997), visual hallucination (Parsons 2016)
Neuromuscular & skeletal: Increased creatine phosphokinase in blood specimen, rhabdomyolysis (Bilgir 2009; Choi 2017; Coupal 2017; Lipson 2005; Tuccori 2007)
Respiratory: Respiratory depression (FDA 2019)
Hypersensitivity to gabapentin or any component of the formulation
Disease-related concerns:
• Myasthenia gravis: Use with caution in patients with myasthenia gravis; may exacerbate condition (Mehrizi 2012).
• Renal impairment: Use with caution in patients with renal impairment; dose adjustment required.
• Seizure disorder: The safety and efficacy of the ER formulation has not been studied in patients with epilepsy.
• Substance abuse: Use with caution in patients with a history of substance abuse, including alcohol, benzodiazepines, cannabis, cocaine, and opioids; potential for drug dependency exists. Tolerance, psychological and physical dependence may occur (Evoy 2017; Mersfelder 2016).
Dosage form specific issues:
• Product interchangeability: IR and ER products are not interchangeable with each other or with gabapentin enacarbil due to differences in formulations, indications, and pharmacokinetics.
Other warnings/precautions:
• Tumorigenic potential: Male rat studies demonstrated an association with pancreatic adenocarcinoma (clinical implication in humans is unknown).
• Withdrawal: Antiseizure medications should not be discontinued abruptly because of the possibility of increasing seizure frequency in patients with epilepsy or other withdrawal symptoms (eg, confusion, irritability, tachycardia, diaphoresis). Therapy should be withdrawn gradually over ≥1 week to minimize the potential of increased seizure frequency, unless safety concerns require a more rapid withdrawal (Norton 2001; Tran 2005).
None known.
Alcohol (Ethyl): CNS Depressants may enhance the CNS depressant effect of Alcohol (Ethyl). Risk C: Monitor therapy
Alizapride: May enhance the CNS depressant effect of CNS Depressants. Risk C: Monitor therapy
Aluminum Hydroxide: May decrease the serum concentration of Gabapentin. Management: Administer gabapentin at least 2 hours after administration of antacids containing aluminum hydroxide or magnesium hydroxide. Risk D: Consider therapy modification
Azelastine (Nasal): May enhance the CNS depressant effect of CNS Depressants. Risk X: Avoid combination
Blonanserin: CNS Depressants may enhance the CNS depressant effect of Blonanserin. Management: Use caution if coadministering blonanserin and CNS depressants; dose reduction of the other CNS depressant may be required. Strong CNS depressants should not be coadministered with blonanserin. Risk D: Consider therapy modification
Brexanolone: CNS Depressants may enhance the CNS depressant effect of Brexanolone. Risk C: Monitor therapy
Brimonidine (Topical): May enhance the CNS depressant effect of CNS Depressants. Risk C: Monitor therapy
Bromopride: May enhance the CNS depressant effect of CNS Depressants. Risk C: Monitor therapy
Bromperidol: May enhance the CNS depressant effect of CNS Depressants. Risk X: Avoid combination
Buprenorphine: CNS Depressants may enhance the CNS depressant effect of Buprenorphine. Management: Consider reduced doses of other CNS depressants, and avoiding such drugs in patients at high risk of buprenorphine overuse/self-injection. Initiate buprenorphine at lower doses in patients already receiving CNS depressants. Risk D: Consider therapy modification
Cannabinoid-Containing Products: CNS Depressants may enhance the CNS depressant effect of Cannabinoid-Containing Products. Risk C: Monitor therapy
Cetirizine (Systemic): May enhance the CNS depressant effect of Gabapentin. Cetirizine (Systemic) may decrease the serum concentration of Gabapentin. Risk C: Monitor therapy
Chlormethiazole: May enhance the CNS depressant effect of CNS Depressants. Management: Monitor closely for evidence of excessive CNS depression. The chlormethiazole labeling states that an appropriately reduced dose should be used if such a combination must be used. Risk D: Consider therapy modification
Chlorphenesin Carbamate: May enhance the adverse/toxic effect of CNS Depressants. Risk C: Monitor therapy
CNS Depressants: May enhance the adverse/toxic effect of other CNS Depressants. Risk C: Monitor therapy
Daridorexant: May enhance the CNS depressant effect of CNS Depressants. Management: Dose reduction of daridorexant and/or any other CNS depressant may be necessary. Use of daridorexant with alcohol is not recommended, and the use of daridorexant with any other drug to treat insomnia is not recommended. Risk D: Consider therapy modification
Desmopressin: Hyponatremia-Associated Agents may enhance the hyponatremic effect of Desmopressin. Risk C: Monitor therapy
Difelikefalin: May enhance the CNS depressant effect of CNS Depressants. Risk C: Monitor therapy
Dimethindene (Topical): May enhance the CNS depressant effect of CNS Depressants. Risk C: Monitor therapy
Doxylamine: May enhance the CNS depressant effect of CNS Depressants. Management: The manufacturer of Diclegis (doxylamine/pyridoxine), intended for use in pregnancy, specifically states that use with other CNS depressants is not recommended. Risk C: Monitor therapy
Droperidol: May enhance the CNS depressant effect of CNS Depressants. Management: Consider dose reductions of droperidol or of other CNS agents (eg, opioids, barbiturates) with concomitant use. Risk D: Consider therapy modification
Esketamine: May enhance the CNS depressant effect of CNS Depressants. Risk C: Monitor therapy
Flunitrazepam: CNS Depressants may enhance the CNS depressant effect of Flunitrazepam. Management: Reduce the dose of CNS depressants when combined with flunitrazepam and monitor patients for evidence of CNS depression (eg, sedation, respiratory depression). Use non-CNS depressant alternatives when available. Risk D: Consider therapy modification
HydrOXYzine: May enhance the CNS depressant effect of CNS Depressants. Risk C: Monitor therapy
Kava Kava: May enhance the CNS depressant effect of CNS Depressants. Risk C: Monitor therapy
Kratom: May enhance the CNS depressant effect of CNS Depressants. Risk X: Avoid combination
Lemborexant: May enhance the CNS depressant effect of CNS Depressants. Management: Dosage adjustments of lemborexant and of concomitant CNS depressants may be necessary when administered together because of potentially additive CNS depressant effects. Close monitoring for CNS depressant effects is necessary. Risk D: Consider therapy modification
LevETIRAcetam: May enhance the CNS depressant effect of Gabapentin. Risk C: Monitor therapy
Lisuride: May enhance the CNS depressant effect of CNS Depressants. Risk C: Monitor therapy
Lofexidine: May enhance the CNS depressant effect of CNS Depressants. Risk C: Monitor therapy
Magnesium Salts: May enhance the CNS depressant effect of Gabapentin. Specifically, high dose intravenous/epidural magnesium sulfate may enhance the CNS depressant effects of gabapentin. Magnesium Salts may decrease the serum concentration of Gabapentin. Management: Administer gabapentin at least 2 hours after use of a magnesium-containing antacid. Monitor patients closely for evidence of reduced response to gabapentin therapy. Monitor for CNS depression if high dose IV/epidural magnesium sulfate is used. Risk D: Consider therapy modification
Mefloquine: May diminish the therapeutic effect of Antiseizure Agents. Mefloquine may decrease the serum concentration of Antiseizure Agents. Management: Mefloquine is contraindicated for malaria prophylaxis in persons with a history of seizures. If antiseizure drugs are being used for another indication, monitor antiseizure drug concentrations and treatment response closely with concurrent use. Risk D: Consider therapy modification
Methotrimeprazine: CNS Depressants may enhance the CNS depressant effect of Methotrimeprazine. Methotrimeprazine may enhance the CNS depressant effect of CNS Depressants. Management: Reduce the usual dose of CNS depressants by 50% if starting methotrimeprazine until the dose of methotrimeprazine is stable. Monitor patient closely for evidence of CNS depression. Risk D: Consider therapy modification
Metoclopramide: May enhance the CNS depressant effect of CNS Depressants. Risk C: Monitor therapy
MetyroSINE: CNS Depressants may enhance the sedative effect of MetyroSINE. Risk C: Monitor therapy
Mianserin: May diminish the therapeutic effect of Antiseizure Agents. Risk C: Monitor therapy
Minocycline (Systemic): May enhance the CNS depressant effect of CNS Depressants. Risk C: Monitor therapy
Olopatadine (Nasal): May enhance the CNS depressant effect of CNS Depressants. Risk X: Avoid combination
Opioid Agonists: CNS Depressants may enhance the CNS depressant effect of Opioid Agonists. Management: Avoid concomitant use of opioid agonists and benzodiazepines or other CNS depressants when possible. These agents should only be combined if alternative treatment options are inadequate. If combined, limit the dosages and duration of each drug. Risk D: Consider therapy modification
Orlistat: May decrease the serum concentration of Antiseizure Agents. Risk C: Monitor therapy
Orphenadrine: CNS Depressants may enhance the CNS depressant effect of Orphenadrine. Risk X: Avoid combination
Oxomemazine: May enhance the CNS depressant effect of CNS Depressants. Risk X: Avoid combination
Oxybate Salt Products: CNS Depressants may enhance the CNS depressant effect of Oxybate Salt Products. Management: Consider alternatives to this combination when possible. If combined, dose reduction or discontinuation of one or more CNS depressants (including the oxybate salt product) should be considered. Interrupt oxybate salt treatment during short-term opioid use Risk D: Consider therapy modification
OxyCODONE: CNS Depressants may enhance the CNS depressant effect of OxyCODONE. Management: Avoid concomitant use of oxycodone and benzodiazepines or other CNS depressants when possible. These agents should only be combined if alternative treatment options are inadequate. If combined, limit the dosages and duration of each drug. Risk D: Consider therapy modification
Paraldehyde: CNS Depressants may enhance the CNS depressant effect of Paraldehyde. Risk X: Avoid combination
Perampanel: May enhance the CNS depressant effect of CNS Depressants. Risk C: Monitor therapy
Piribedil: CNS Depressants may enhance the CNS depressant effect of Piribedil. Risk C: Monitor therapy
Pramipexole: CNS Depressants may enhance the sedative effect of Pramipexole. Risk C: Monitor therapy
Ropeginterferon Alfa-2b: CNS Depressants may enhance the adverse/toxic effect of Ropeginterferon Alfa-2b. Specifically, the risk of neuropsychiatric adverse effects may be increased. Management: Avoid coadministration of ropeginterferon alfa-2b and other CNS depressants. If this combination cannot be avoided, monitor patients for neuropsychiatric adverse effects (eg, depression, suicidal ideation, aggression, mania). Risk D: Consider therapy modification
ROPINIRole: CNS Depressants may enhance the sedative effect of ROPINIRole. Risk C: Monitor therapy
Rotigotine: CNS Depressants may enhance the sedative effect of Rotigotine. Risk C: Monitor therapy
Rufinamide: May enhance the adverse/toxic effect of CNS Depressants. Specifically, sleepiness and dizziness may be enhanced. Risk C: Monitor therapy
Suvorexant: CNS Depressants may enhance the CNS depressant effect of Suvorexant. Management: Dose reduction of suvorexant and/or any other CNS depressant may be necessary. Use of suvorexant with alcohol is not recommended, and the use of suvorexant with any other drug to treat insomnia is not recommended. Risk D: Consider therapy modification
Thalidomide: CNS Depressants may enhance the CNS depressant effect of Thalidomide. Risk X: Avoid combination
Trimeprazine: May enhance the CNS depressant effect of CNS Depressants. Risk C: Monitor therapy
Valerian: May enhance the CNS depressant effect of CNS Depressants. Risk C: Monitor therapy
Zolpidem: CNS Depressants may enhance the CNS depressant effect of Zolpidem. Management: Reduce the Intermezzo brand sublingual zolpidem adult dose to 1.75 mg for men who are also receiving other CNS depressants. No such dose change is recommended for women. Avoid use with other CNS depressants at bedtime; avoid use with alcohol. Risk D: Consider therapy modification
Tablet, solution (immediate release): No significant effect on rate or extent of absorption; extended release tablet: Increases rate and extent of absorption. Management: Administer immediate release products without regard to food. Administer extended release with food.
Extended release tablet should be taken with food.
Folic acid supplementation is recommended prior to pregnancy in women using gabapentin (Borgelt 2016; Picchietti 2015).
Gabapentin crosses the placenta. In a small study (n=6), the umbilical/maternal plasma concentration ratio was ~1.74. Neonatal concentrations declined quickly after delivery and at 24 hours of life were ~27% of the cord blood concentrations at birth (gabapentin neonatal half-life ~14 hours) (Ohman 2005). Pregnancy registry outcome data following maternal use of gabapentin during pregnancy is limited (Holmes 2012). Folic acid supplementation is recommended during pregnancy in women using gabapentin (Borgelt 2016; Picchietti 2015).
Gabapentin is used off-label for the treatment of restless leg syndrome; however, current guidelines note there is insufficient evidence to recommend its use in pregnant women for this indication (Picchietti 2015). Pharmacological agents should not be used for the treatment of alcohol use disorder in pregnant women unless needed for the treatment of acute alcohol withdrawal or a coexisting disorder.
Patients exposed to gabapentin during pregnancy are encouraged to enroll in the North American Antiepileptic Drug (NAAED) Pregnancy Registry by calling 1-888-233-2334. Additional information is available at www.aedpregnancyregistry.org.
Seizure frequency and duration; renal function; weight; behavior in children; signs and symptoms of suicidality (eg, anxiety, depression, behavior changes)
Routine monitoring of drug levels is not required; a specific target serum concentration range for antiseizure response has not been established (Lindberger 2003); a minimum effective serum concentration may be 2 mcg/mL (Krasowski 2010)
Gabapentin is structurally related to GABA. However, it does not bind to GABAA or GABAB receptors, and it does not appear to influence degradation or uptake of GABA. High affinity gabapentin binding sites have been located throughout the brain; these sites correspond to the presence of voltage-gated calcium channels specifically possessing the alpha-2-delta-1 subunit. This channel appears to be located presynaptically, and may modulate the release of excitatory neurotransmitters which participate in epileptogenesis and nociception. These effects on restless leg syndrome are unknown.
Absorption: Variable, from proximal small bowel by L-amino transport system; saturable process; dose-dependent
Distribution: Vd: 58 ± 6 L; CSF concentrations are ~20% of plasma concentrations
Protein binding: <3%
Metabolism: Not metabolized
Bioavailability: Inversely proportional to dose due to saturable absorption:
Immediate release:
900 mg/day: 60%
1,200 mg/day: 47%
2,400 mg/day: 34%
3,600 mg/day: 33%
4,800 mg/day: 27%
Extended release: Variable; increased with higher fat content meal
Half-life elimination:
Infants 1 month to Children 12 years: 4.7 hours
Adults, normal: 5 to 7 hours; increased half-life with decreased renal function; anuric adult patients: 132 hours; adults during hemodialysis: 3.8 hours
Time to peak: Immediate release: Infants 1 month to Children 12 years: 2 to 3 hours; Adults: 2 to 4 hours; Extended release: 8 hours
Excretion: Proportional to renal function; urine (as unchanged drug)
Clearance: Apparent oral clearance is directly proportional to CrCl: Clearance in infants is highly variable; oral clearance (per kg) in children <5 years of age is higher than in children ≥5 years of age
Renal function impairment: In CrCl <30 mL/minute, half-life is approximately 52 hours (immediate release). In moderate and severe renal impairment, Cl was decreased to 3 and 1 L/hour, respectively, compared with 5 to 7 L/hour in nonrenal impairment patients (ER).
Note: Commercial oral solution is available (50 mg/mL)
A 100 mg/mL suspension may be made with tablets (immediate release) and either a 1:1 mixture of Ora-Sweet® (100 mL) and Ora-Plus® (100 mL) or 1:1 mixture of methylcellulose 1% (100 mL) and Simple Syrup N.F. (100 mL). Crush sixty-seven 300 mg tablets in a mortar and reduce to a fine powder. Add small portions of the chosen vehicle and mix to a uniform paste; mix while adding the vehicle in incremental proportions to almost 200 mL; transfer to a calibrated bottle, rinse mortar with vehicle, and add sufficient quantity of vehicle to make 200 mL. Label "shake well" and "refrigerate". Stable for 91 days refrigerated (preferred) or 56 days at room temperature.
Capsules (Gabapentin Oral)
100 mg (per each): $0.11 - $0.61
300 mg (per each): $0.15 - $2.67
400 mg (per each): $0.18 - $1.60
Capsules (Neurontin Oral)
100 mg (per each): $2.95
300 mg (per each): $7.37
400 mg (per each): $8.84
Misc (Gralise Oral)
300 (9) &600(24) MG (per each): $0.00
Solution (Gabapentin Oral)
250 mg/5 mL (per mL): $0.32 - $0.83
Solution (Neurontin Oral)
250 mg/5 mL (per mL): $1.11
Tablets (Gabapentin Oral)
600 mg (per each): $0.33 - $2.79
800 mg (per each): $0.39 - $3.36
Tablets (Gralise Oral)
300 mg (per each): $11.53
600 mg (per each): $11.53
Tablets (Neurontin Oral)
600 mg (per each): $14.00
800 mg (per each): $16.79
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