Gabapentin
Gabapentin is a prescription gabapentinoid marketed for partial seizures and postherpetic neuralgia, widely used off-label for neuropathic pain, anxiety and sleep. Despite the name it does not act on GABA receptors; it binds the alpha-2-delta subunit of voltage-gated calcium channels. It is calming and sedating at higher doses, has meaningful misuse potential (especially with opioids), and produces a genuine physical withdrawal syndrome on abrupt cessation.
01 Overview
Gabapentin has extensive human data across epilepsy, neuropathic pain and restless legs syndrome. Oral bioavailability falls as dose rises because absorption relies on a saturable transporter, so blood levels do not scale linearly with the dose.
Recreational and self-medicated use for its calming, mildly euphoric or opioid-potentiating effects has grown, and it is increasingly detected in overdose deaths alongside opioids. Physical dependence develops with sustained use and abrupt withdrawal can trigger anxiety, insomnia, sweating and rarely seizures, so tapering is standard.
02 Mechanism
Binds the alpha-2-delta-1 auxiliary subunit of voltage-gated calcium channels, reducing presynaptic calcium influx and the release of excitatory neurotransmitters. It does not bind GABA-A or GABA-B receptors despite the structural resemblance to GABA.
03 Dosing
| Tier | Dose | Route | Notes |
|---|---|---|---|
| Anxiolytic (off-label) | 300–900 mg/day | Oral | Off-label; start low to limit sedation and dizziness. |
| Neuropathic pain | 900–3600 mg/day | Oral | Titrated over days, split into three doses; higher end limited by saturable absorption. |
04 Effects
| Effect | Magnitude | Evidence | |
|---|---|---|---|
| Anxiolysis and calmingReduces situational and generalised anxiety in several trials; also used peri-operatively to reduce anticipatory anxiety. | Moderate | Clinical | |
| Neuropathic pain reliefReduces burning and shooting pain in postherpetic neuralgia and diabetic neuropathy. | NNT ~6-8 | Clinical | |
| Improved sleep onsetSedation and reduced sleep latency, partly secondary to pain and anxiety relief. | Moderate | Clinical |
05 Side effects
| Effect | Severity | Frequency | Evidence | Countermeasures |
|---|---|---|---|---|
| Sedation and dizzinessDrowsiness, unsteadiness and dizziness, most pronounced during titration. | Mild | Very common | Clinical | |
| Withdrawal syndromeAbrupt cessation causes anxiety, insomnia, sweating, nausea and rarely seizures. | Moderate | Common after chronic use | Clinical | |
| Respiratory depression with opioidsCombining with opioids or other CNS depressants can suppress breathing and has contributed to overdose deaths. | Life-threatening | Uncommon but serious | Clinical |