NEURONTIN
Clinical safety rating: caution
Comprehensive clinical and safety monograph for NEURONTIN (NEURONTIN).
Gabapentin binds to the α2δ subunit of voltage-gated calcium channels, inhibiting calcium influx and reducing neurotransmitter release, particularly glutamate, norepinephrine, and substance P. It does not interact with GABA receptors.
| Metabolism | Gabapentin does not undergo hepatic metabolism; it is excreted unchanged in urine. No involvement of cytochrome P450 enzymes. |
| Excretion | Renal elimination as unchanged drug: >90%; 0.3% is excreted in feces; biliary elimination is negligible. |
| Half-life | Terminal elimination half-life is 5–7 hours in patients with normal renal function; in elderly or those with renal impairment, half-life may be prolonged up to 132 hours; requires dose adjustment for creatinine clearance <60 mL/min. |
| Protein binding | <3% bound to plasma proteins (negligible). |
| Volume of Distribution | Volume of distribution is 0.8 L/kg (57 L in a 70 kg adult), indicating distribution into total body water. |
| Bioavailability | Oral bioavailability is approximately 60% (30–90% with interindividual variability); decreases with higher doses due to saturable absorption; not affected by food. |
| Onset of Action | Oral: Peak plasma concentrations occur 2–4 hours after dosing; clinical effect onset may be within 1–2 weeks for neuropathic pain and epilepsy. |
| Duration of Action | Duration of action is approximately 8–12 hours based on dosing interval (typically TID); steady-state achieved by 1–2 days. |
300 mg orally once daily on day 1, 300 mg twice daily on day 2, then 300 mg three times daily on day 3; titrate up to effective dose, usual maintenance 300-600 mg three times daily, maximum 3600 mg/day.
| Dosage form | CAPSULE |
| Renal impairment | For CrCl 30-59 mL/min: 200-700 mg twice daily. For CrCl 15-29 mL/min: 200-700 mg once daily. For CrCl <15 mL/min: 100-300 mg once daily. Hemodialysis: loading dose 300-400 mg, then 200-300 mg after each 4-hour dialysis session. |
| Liver impairment | No specific dose adjustment guidelines; pharmacokinetics unchanged in hepatic impairment per manufacturer. |
| Pediatric use | For epilepsy (ages 3-12): initial 10-15 mg/kg/day in 3 divided doses, titrate over 3 days to effective dose, maintenance 25-35 mg/kg/day in 3 divided doses; maximum 50 mg/kg/day. For postherpetic neuralgia: not indicated. |
| Geriatric use | Initiate at lower dose (e.g., 100-300 mg/day) and titrate slowly; monitor for dizziness, sedation, and renal function; adjust dose based on creatinine clearance. |
| 1st trimester | Consult provider |
| 2nd trimester | Consult provider |
| 3rd trimester | Consult provider |
Clinical note
Comprehensive clinical and safety monograph for NEURONTIN (NEURONTIN).
| Breastfeeding | Gabapentin is excreted into human milk; M/P ratio approximately 1.0. Limited data suggest low infant exposure (relative infant dose <2% of maternal weight-adjusted dose). Monitor infant for drowsiness, poor feeding, and gastrointestinal disturbances. Benefit of breastfeeding should be weighed against potential risks. |
| Teratogenic Risk | First trimester: Increased risk of major congenital malformations (e.g., neural tube defects, heart defects) based on epidemiological data; avoid use if possible. Second and third trimester: Risk of fetal growth restriction, preterm birth, and neonatal withdrawal symptoms (e.g., feeding difficulties, irritability) after in utero exposure. |
■ FDA Black Box Warning
None.
| Serious Effects |
["Hypersensitivity to gabapentin or any component of the formulation"]
| Precautions | ["Respiratory depression: risk increased with opioid coadministration or in elderly patients","Central nervous system effects: dizziness, somnolence, ataxia","Increased seizure frequency with abrupt withdrawal","Suicidal behavior and ideation","Anaphylaxis and angioedema","Drug reaction with eosinophilia and systemic symptoms (DRESS)","Pancreatitis","Abrupt discontinuation may precipitate status epilepticus in patients with seizures"] |
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| Fetal Monitoring | Maternal: Therapeutic drug monitoring of gabapentin levels is not routinely recommended but may be considered if toxicity suspected. Monitor for signs of CNS depression, dizziness, and ataxia. Fetal/Neonatal: Ultrasound for fetal growth and anatomy, especially if first-trimester exposure. Newborn assessment for withdrawal symptoms for 48-72 hours post-delivery. |
| Fertility Effects | No significant adverse effects on fertility in animal studies. In humans, no conclusive evidence of impaired fertility; however, limited data exist. Gabapentin may affect reproductive hormones (e.g., decrease in testosterone) in males, but clinical significance unclear. |