Gabapentin !
A nerve-pain and add-on seizure medicine that binds a calcium channel subunit. It causes drowsiness and dizziness and leaves the body by the kidneys.
Updated 2026-11-01
The figure shows gabapentin bound to the α2δ-1 subunit (from rabbit) in a complex with the human Cav1.2 calcium channel.
Mechanism of action
Gabapentin looks like GABA but does not act on GABA receptors or GABA metabolism. It binds the α2δ-1 subunit of voltage-gated calcium channels, which is thought to reduce calcium entry at overactive nerve terminals and the release of excitatory transmitters.
- Binds the α2δ-1 subunit of voltage-gated calcium channels
- Fewer active channels at presynaptic terminals
- Less release of excitatory transmitters
- Nerve pain and seizure spread are dampened
Pharmacokinetics
- Absorption
- Absorbed by mouth; aluminium or magnesium antacids reduce absorption
- Metabolism
- Not metabolized
- Elimination
- Unchanged in the urine; the dose is adjusted in kidney disease
- Half-life
- About 5 to 7 hours
Indications
- Postherpetic neuralgia (pain after shingles) Herpes zoster (shingles) →
- Add-on treatment of focal seizures Epilepsy and seizures →
Adverse effects
Common
- Drowsiness
- Dizziness
- Unsteadiness (ataxia)
Contraindications
- Hypersensitivity to gabapentin
Key interactions
- Opioids and other central nervous system depressants
- Serious, sometimes fatal respiratory depression
- Aluminium or magnesium antacids
- Less gabapentin absorbed; it is usually separated from them
- Alcohol
- More drowsiness and dizziness
What is monitored
- Sedation and breathing, especially with opioids
- Kidney function
- Mood and suicidal thoughts
- Signs of misuse
Administration and safety
- Given by mouth
- Separated from aluminium or magnesium antacids
- Withdrawn gradually
Nursing care
- Check sedation and breathing, especially when an opioid is also given
- Teach about dizziness and the risk of falls
- Teach to report rash, fever or facial swelling
- Ask about kidney disease before the first dose
Pregnancy and breastfeeding
Human data are limited; a neonatal withdrawal syndrome has been reported after exposure in pregnancy.
Test yourself
Think of the answer, then tap the question to see it.
Does gabapentin act on GABA receptors?
No. Despite its GABA-like structure it binds the α2δ-1 subunit of voltage-gated calcium channels.
Which pain condition is a labelled indication of gabapentin?
Postherpetic neuralgia, the pain that can persist after shingles.
Why must gabapentin be used carefully with opioids?
The combination can cause serious, even fatal, respiratory depression.
Related drugs
Related conditions
← Back to the class: Gabapentinoids
Educational content on how drugs work; not a prescribing guide and no substitute for a health professional's advice. No doses are given.
Sources: Gabapentin: MedlinePlus Drug Information (MedlinePlus (U.S. National Library of Medicine), 2020); DailyMed - GABAPENTIN capsule (DailyMed (U.S. National Library of Medicine), 2026); ATCDDD - ATC/DDD Index (WHO Collaborating Centre for Drug Statistics Methodology, 2026).
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Representative model, for educational purposes only.