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Gabapentin: Difference between revisions

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Comprehensive categorization: +Calcium channel blockers (T-type or N/P/Q-type), Anticonvulsants / Antiepileptics
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{{MedTemplate
{{MedTemplate
| generic           = Gabapentin
| generic           = Gabapentin
| brand             = Neurontin
| brand             = Neurontin (IR), Gralise (ER), Horizant (gabapentin enacarbil ER)
| structure         =  
| structure         =
| classes           = Gabapentinoid, Anticonvulsant
| classes           = [[:Category:Gabapentinoids|Gabapentinoid]], [[:Category:Anticonvulsants|Anticonvulsant]], [[:Category:Neuropathic pain medicines|Neuropathic pain medicine]]
| mechanism          = Alpha-2-delta voltage-gated calcium channel ligand
| uses              = <vote slug="partial-seizures-adjunct-use">Partial-onset seizures (adjunctive, FDA)</vote>, <vote slug="postherpetic-neuralgia-use">Postherpetic neuralgia (FDA)</vote>, <vote slug="restless-legs-syndrome-use">Restless legs syndrome (Horizant, FDA)</vote>, <vote slug="neuropathic-pain-broad-use">Neuropathic pain (off-label, broad)</vote>, <vote slug="fibromyalgia-use">Fibromyalgia (off-label)</vote>, <vote slug="anxiety-gabapentin-use">Anxiety disorders (off-label, evidence mixed)</vote>, <vote slug="aud-gabapentin-use">Alcohol use disorder (off-label)</vote>, <vote slug="menopausal-hot-flashes-use">Menopausal hot flashes (off-label)</vote>
| uses              =  
| starting_dose    = 300 mg PO at bedtime night 1, 300 mg BID day 2, 300 mg TID day 3; titrate to clinical effect, commonly 1800-3600 mg/day divided TID
| starting_dose     =  
| preparations     = Capsules 100, 300, 400 mg; tablets 600, 800 mg; oral solution 250 mg/5 mL; Gralise ER tablets 300, 600 mg (once-daily); Horizant ER tablets 300, 600 mg (gabapentin enacarbil, an inactive parent compound metabolized to gabapentin in vivo)
| preparations      =  
| fda_max          = 3600 mg/day; off-label doses higher are common but bioavailability saturates well below this
| fda_max           =  
| pill_id           =
| routes             =  
| routes           = Oral
| onset             =  
| onset             = 1-2 weeks for neuropathic pain and anxiolytic effect; anticonvulsant effect at therapeutic plasma level
| duration           =  
| duration         = TID dosing for IR; once-daily for ER formulations
| halflife           =
| halflife          = 5-7 hours<ref name="neurontin-label">FDA Prescribing Information, Neurontin (gabapentin), Pfizer, current revision. https://www.accessdata.fda.gov/drugsatfda_docs/label/2017/020235s064_020882s047_021129s046lbl.pdf</ref>
| bioavailability    =
| bioavailability  = '''Saturable''' via the LAT-1 amino-acid transporter, producing nonlinear pharmacokinetics: ~60% at 300 mg single dose, falling to ~35% at 1200 mg single dose<ref name="neurontin-label" />
| pregnancy         =  
| pregnancy        = Limited human data; some signal for cardiac malformations and developmental delay but confounded by maternal disease and polytherapy.{{citation needed}}
| legal              =  
| legal             = [[USLegal:Prescription only|Rx-only]] federally in US. State-level scheduling: '''Schedule V''' in Kentucky, Tennessee, Virginia, North Dakota, Michigan, Alabama, Utah, Wyoming, North Carolina, Mississippi, Louisiana, Connecticut, Ohio (and growing), reflecting documented misuse and overdose-potentiation in combination with opioids<ref name="neurontin-label" />
| intro              =  
| mechanism         = <vote slug="gabapentin-mech-claim">Despite the name, gabapentin does '''not''' bind GABA receptors or affect GABA reuptake. It binds the α2δ-1 auxiliary subunit of voltage-gated calcium channels, reducing presynaptic Ca²⁺ influx and consequent release of excitatory neurotransmitters (glutamate, substance P, norepinephrine, calcitonin gene-related peptide). The pain and anticonvulsant effects share this presynaptic-excitability dampening mechanism.</vote> Saturable LAT-1 absorption is the dominant clinical-pharmacokinetic quirk and explains why dose increases above ~1800 mg/day yield diminishing plasma exposure. Horizant addresses this through the enacarbil parent compound, which is absorbed by non-saturable transporters and then metabolized to gabapentin in vivo<ref name="neurontin-label" />.
| pharmacokinetics   =  
| pharmacodynamics  =  
| indications        =
| dosing             =  
| effects            =  
| interactions      = <pharmaInteractions/>
| pregnancy_details  =
| monitoring         =  
| counseling        =  
| anecdotes          =
| seealso            =
| references        =  
}}
}}


== References ==
<references />


[[Category:Stimulants & Wake-Promoting Agents]]
[[Category:Gabapentinoids]]
[[Category:GABAergics]]
[[Category:Anticonvulsants]]
[[Category:Sedative-Hypnotics]]
[[Category:Neuropathic pain medicines]]
[[Category:Calcium channel blockers (T-type or N/P/Q-type)]]
[[Category:Anticonvulsants / Antiepileptics]]

Latest revision as of 06:22, 23 May 2026

Gabapentinoid, Anticonvulsant, Neuropathic pain medicine
Gabapentin
Neurontin (IR), Gralise (ER), Horizant (gabapentin enacarbil ER)

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Problems

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Titration strategies

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Effects

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Summary
Classes
Gabapentinoid, Anticonvulsant, Neuropathic pain medicine
Pharmacy
Starting dose
300 mg PO at bedtime night 1, 300 mg BID day 2, 300 mg TID day 3; titrate to clinical effect, commonly 1800-3600 mg/day divided TID
Preparations
Capsules 100, 300, 400 mg; tablets 600, 800 mg; oral solution 250 mg/5 mL; Gralise ER tablets 300, 600 mg (once-daily); Horizant ER tablets 300, 600 mg (gabapentin enacarbil, an inactive parent compound metabolized to gabapentin in vivo)
US FDA Max
3600 mg/day; off-label doses higher are common but bioavailability saturates well below this
Pharmacology
Routes
Oral
Onset
1-2 weeks for neuropathic pain and anxiolytic effect; anticonvulsant effect at therapeutic plasma level
Duration
TID dosing for IR; once-daily for ER formulations
Half-life
5-7 hours[1]
Bioavailability
Saturable via the LAT-1 amino-acid transporter, producing nonlinear pharmacokinetics: ~60% at 300 mg single dose, falling to ~35% at 1200 mg single dose[1]
Pregnancy
Limited human data; some signal for cardiac malformations and developmental delay but confounded by maternal disease and polytherapy.[citation needed]
Legal status
Rx-only federally in US. State-level scheduling: Schedule V in Kentucky, Tennessee, Virginia, North Dakota, Michigan, Alabama, Utah, Wyoming, North Carolina, Mississippi, Louisiana, Connecticut, Ohio (and growing), reflecting documented misuse and overdose-potentiation in combination with opioids[1]
Purported mechanism
Despite the name, gabapentin does not bind GABA receptors or affect GABA reuptake. It binds the α2δ-1 auxiliary subunit of voltage-gated calcium channels, reducing presynaptic Ca²⁺ influx and consequent release of excitatory neurotransmitters (glutamate, substance P, norepinephrine, calcitonin gene-related peptide). The pain and anticonvulsant effects share this presynaptic-excitability dampening mechanism.0 Saturable LAT-1 absorption is the dominant clinical-pharmacokinetic quirk and explains why dose increases above ~1800 mg/day yield diminishing plasma exposure. Horizant addresses this through the enacarbil parent compound, which is absorbed by non-saturable transporters and then metabolized to gabapentin in vivo[1].

References

  1. ↑ 1.0 1.1 1.2 1.3 FDA Prescribing Information, Neurontin (gabapentin), Pfizer, current revision. https://www.accessdata.fda.gov/drugsatfda_docs/label/2017/020235s064_020882s047_021129s046lbl.pdf
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