Gabapentin: Difference between revisions
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{{MedTemplate | {{MedTemplate | ||
| generic | | generic = Gabapentin | ||
| brand | | brand = Neurontin (IR), Gralise (ER), Horizant (gabapentin enacarbil ER) | ||
| structure | | structure = | ||
| classes | | classes = [[:Category:Gabapentinoids|Gabapentinoid]], [[:Category:Anticonvulsants|Anticonvulsant]], [[:Category:Neuropathic pain medicines|Neuropathic pain medicine]] | ||
| | | 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> | ||
| | | 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) | ||
| | | fda_max = 3600 mg/day; off-label doses higher are common but bioavailability saturates well below this | ||
| | | 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 = '''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 = Limited human data; some signal for cardiac malformations and developmental delay but confounded by maternal disease and polytherapy.{{citation needed}} | |||
| 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" /> | |||
| | | 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" />. | ||
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== References == | |||
<references /> | |||
[[Category: | [[Category:Gabapentinoids]] | ||
[[Category: | [[Category:Anticonvulsants]] | ||
[[Category:Neuropathic pain medicines]] | |||
[[Category: | |||