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.

• GabapentinThe 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.
• PregabalinUK reports of abuse and dependence with pregabalin far outnumber those with gabapentin, and its US label records euphoria in some patients.

• Neuropathic pain, such as diabetic neuropathy
• Postherpetic neuralgia (pain after shingles)
• Focal seizures, usually as add-on treatment
• Fibromyalgia (pregabalin)
• Generalized anxiety disorder (pregabalin)
• Restless legs syndrome (gabapentin enacarbil)

• DizzinessKnown for
• Drowsiness and sedationKnown for
• Swollen ankles and legs (peripheral edema)Known for
• Unsteadiness and poor coordination (ataxia)
• Weight gain
• Blurred or double vision
• Breathing depression, mainly with opioidsSerious
• Misuse and dependenceSerious
• Withdrawal symptoms if stopped suddenly
• Suicidal thoughtsSerious

What the class has in common. Each drug's card has its own, and Known for marks what an exam expects you to know.

• With opioids, benzodiazepines or other CNS depressants, or in COPD or old age, they can cause serious, even fatal, breathing depression.
• They are misused, often alongside opioids; check for past drug misuse and watch for dose escalation. Both are Class C drugs in the UK.
• Both are cleared unchanged by the kidneys, so doses are reduced in kidney impairment.
• Stop gradually over at least a week: sudden withdrawal brings insomnia, nausea, anxiety and sweating, and can raise seizure frequency.

Written for biofideX in plain words, after checking these references:

• Gabapentin capsules: label (DailyMed)
• Pregabalin capsules: label (DailyMed)
• Pregabalin (NCI Thesaurus)
• Gabapentin and pregabalin: Drug Safety Communication, serious breathing problems (FDA)
• Pregabalin, gabapentin and risk of abuse and dependence: new scheduling requirements (MHRA)
• Pregabalin: product information (EMA)

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.