Gabapentinoids · Neurology
Gabapentin
Neurontin®(brand names vary by market)
Named after GABA, and it does not touch it.
Also: tablet, oral liquid
Mechanism
Binds the alpha-2-delta subunit of voltage-gated calcium channels, reducing excitatory neurotransmitter release. Despite the name it has no direct action at GABA receptors.
Indications
- Neuropathic pain
- Focal seizures, as adjunct
- Restless legs syndrome
Formulations
Dosing concepts
Renal dosing
Entirely renally cleared and unmetabolised, so dose and interval track creatinine clearance closely. This is one of the most frequently missed renal adjustments in practice.
Saturable absorption
Absorbed by a saturable transporter, so bioavailability falls as the dose rises: doubling the dose does not double the exposure, and splitting it works better.
Titration
Started low and increased over weeks; abrupt introduction produces sedation and dizziness that end the trial early.
Concepts, not prescribing instructions. Practice numbers live in current references and local protocols.
Pharmacokinetics
- Bioavailability
- ~60% at low doses, falling to ~30% at high doses
- Half-life
- 5 to 7 h with normal renal function, greatly prolonged in impairment
- Elimination
- renal: Excreted unchanged; no hepatic metabolism and essentially no interactions
- Protein binding
- Negligible
Adverse effects
- Sedation and dizzinesscommonThe commonest reason it is abandoned; slower titration usually fixes it.
- Peripheral oedemacommonOften mistaken for heart failure and answered with a diuretic, which is a prescribing cascade.
- Weight gaincommon
- Respiratory depression with opioidsseriousA recognised and under-appreciated combination risk.
- Accumulation in renal impairmentseriousPresents as confusion, myoclonus and profound sedation.
- MisuseseriousIncreasingly recognised, particularly alongside opioids.
Contraindications & precautions
Contraindications
- Known hypersensitivity
Precautions
- Renal impairment
- Older adults
- Concurrent opioids or sedatives
- History of substance use
Interactions
No curated interaction entries yet for this agent.
Monitoring
Renal function
It sets the dose entirely · Baseline and with any change in kidney function
Sedation, gait and confusion
Accumulation presents this way before any test does
Whether it is working
Neuropathic pain agents that have not helped after an adequate trial should be stopped, not continued indefinitely
Counselling points
- We will build the dose up slowly; drowsiness usually settles.
- Do not drive until you know how it affects you.
- Do not stop it suddenly.
- Antacids reduce absorption; separate them by two hours.
- Tell us if your ankles swell.
Clinical pearls
- A confused older patient on gabapentin whose kidneys have declined is a classic and reversible presentation. The dose never changed; the clearance did.
- Its ankle oedema is routinely treated with furosemide by someone who has not connected the two, which then produces its own problems. Recognising it is worth a great deal.
References & review
- Gabapentin product monograph (consult the current version for your market) (monograph)
- Goodman & Gilman's The Pharmacological Basis of Therapeutics, 14th ed. (reference-work)
Last reviewed 2026-08-16 · jurisdiction: global · drug information changes; verify against current references before practice use.