Gabapentin (Neurontin): Uses, Risks, and Off-Label Psychiatric Prescribing

Gabapentin (brand name: Neurontin) is a gabapentinoid (anticonvulsant analog of gaba). Despite its name, gabapentin does not act on GABA receptors. It binds to the alpha-2-delta subunit of voltage-gated calcium channels, reducing calcium influx and neurotransmitter release (particularly glutamate, norepinephrine, and substance P). This reduces neuronal excitability, which produces anticonvulsant, analgesic, and anxiolytic effects. Its calming effect differs mechanistically from benzodiazepines, though subjective effects can overlap.

• Epilepsy (adjunctive for partial seizures)
• Postherpetic neuralgia (nerve pain after shingles)

Common off-label uses:

• Generalized Anxiety Disorder
• Social Anxiety Disorder
• Insomnia
• Alcohol withdrawal
• Neuropathic pain (various types)
• Restless Legs Syndrome
• Hot flashes
• Fibromyalgia

Anxiety: 300-600 mg three times daily (start 300 mg at bedtime, increase every 3-5 days). Insomnia: 300-600 mg at bedtime. Neuropathic pain: 300-1200 mg three times daily. Maximum ~3600 mg/day. Renal dosing required. Absorption is nonlinear — bioavailability decreases at higher single doses (split doses recommended).

Takes 1-2 weeks for full anxiolytic effect. Single-dose sedative effect within 1-2 hours.

• Drowsiness and sedation
• Dizziness
• Peripheral edema
• Weight gain
• Cognitive impairment ('gabapentin fog')
• Ataxia and unsteadiness
• Visual disturbances

• Respiratory depression when combined with opioids or CNS depressants (FDA warning added 2019)
• Suicidal ideation (anticonvulsant class warning)
• Misuse and dependence potential (increasingly recognized — some states now schedule it)
• Severe withdrawal (seizures, psychosis) with abrupt discontinuation after chronic use
• Anaphylaxis and angioedema (rare)

Increases risk of respiratory depression with opioids, benzodiazepines, and alcohol. Antacids reduce absorption by ~20%. Morphine increases gabapentin levels. No significant CYP450 interactions (renally cleared).

Category C. Limited human data. Animal studies show some risk. Use only if clearly needed.

Taper gradually over 1-2 weeks minimum. Abrupt discontinuation after chronic use can cause seizures, insomnia, anxiety, pain, and nausea. Longer tapers needed at higher doses.