Gabapentin
A gabapentinoid for nerve pain, such as postherpetic neuralgia, and for focal seizures, usually alongside other antiepileptics.
Drug card
- Class
- Gabapentinoid
- How it works
- Binding the alpha-2-delta calcium channel subunit to cut transmitter release
- Used for
- Postherpetic neuralgia (nerve pain after shingles)
- Peripheral nerve pain, such as diabetic neuropathy
- Focal seizures, as add-on or (in the UK) alone
- Known for
- Drowsiness and sedation
- Dizziness
- Swollen ankles and legs (peripheral edema)
- Its name
- -gab- means a GABA analogue (gabapentin type)
Study it as a flashcard, and it comes back before you forget it.
Mechanism of action
How does gabapentin work?
Gabapentin is a GABA analogue that binds the alpha-2-delta subunit of voltage-activated calcium channels, though how this produces its effects is unknown; it does not alter GABA binding, uptake or breakdown. The share of each dose absorbed falls as the dose rises, and it leaves unchanged in the urine, so its clearance tracks kidney function.
Like other gabapentinoids: Gabapentinoids bind the alpha-2-delta subunit of the voltage-gated calcium channels found in the brain and spinal cord. This cuts calcium entry into overactive nerve endings and so the release of glutamate, norepinephrine and substance P, damping pain signals and seizure spread, though the full mechanism is not settled. Although built like GABA, they do not act on GABA receptors or change GABA levels.
Uses
What is gabapentin used for?
- Postherpetic neuralgia (nerve pain after shingles)
- Peripheral nerve pain, such as diabetic neuropathy
- Focal seizures, as add-on or (in the UK) alone
Side effects
Side effects of gabapentin
- Drowsiness and sedationKnown for
- DizzinessKnown for
- Swollen ankles and legs (peripheral edema)Known for
- Tiredness
- Blurred or double vision, nystagmus
- Breathing depression, mainly with opioidsSerious
- Misuse and dependenceSerious
- DRESS (multiorgan hypersensitivity)Serious
- Stevens-Johnson syndrome (rare)Serious
- Hostility and mood swings in children aged 3 to 12
- Low sodium (hyponatremia), rareSerious
- Muscle breakdown (rhabdomyolysis), rareSerious
Known for marks what an exam expects you to know it for.
Watch for
Cautions and what sets it apart
- Breathing depression, sometimes fatal, is likeliest with opioids or other sedatives, in COPD and in older people.
- Misuse and dependence occur, mostly in people with past drug misuse; it is a Class C controlled drug in the UK.
- It is cleared unchanged by the kidneys, so doses are reduced in kidney impairment and often in older people.
- Aluminum or magnesium antacids cut its absorption; stopping abruptly can trigger seizures in epilepsy.
Good to know: The share absorbed falls from about 60% at low doses to under 30% at the highest, unlike pregabalin, which is absorbed almost completely at every dose.
Remember it
A way to remember it
Gabapentinoids look like GABA but act on calcium.
They are built like the neurotransmitter GABA yet do not bind GABA receptors; instead they bind the alpha-2-delta subunit of voltage-gated calcium channels and cut transmitter release.
Written for biofideX
Its name
-gab- means GABA analogue (gabapentin type)
Gabapentin and pregabalin are modeled on GABA, but both bind the alpha-2-delta subunit of calcium channels, and gabapentin leaves GABA binding and breakdown untouched.
- Every drug name stem
Its class
Gabapentinoids
Other gabapentinoids with a card:
Easily mixed up with benzodiazepines, tricyclic antidepressants and serotonin-norepinephrine reuptake inhibitors.
Sources
Checked against
Written for biofideX in plain words, after checking these references:
- Gabapentin capsules: label (DailyMed)
- Gabapentin (NCI Thesaurus)
- About gabapentin (NHS)
- Gabapentin and pregabalin: Drug Safety Communication, serious breathing problems (FDA)
- Pregabalin, gabapentin and risk of abuse and dependence: new scheduling requirements (MHRA)
For learning pharmacology, not for treatment decisions: no doses are given, and a prescriber, pharmacist or the product's own label is the word on any one patient. Spotted a mistake? Tell us and we'll correct it.
Epilepsy and nerve pain
Gabapentin is one of 8 drugs practiced together here: their classes, how they work, what they treat and what they're known for.
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