Gabapentin
Neurontin · Gralise · Horizant
Gabapentinoid (α2δ voltage-gated calcium channel modulator)
Binds the α2δ subunit of presynaptic voltage-gated Ca²⁺ channels → ↓ excitatory neurotransmitter release. Anticonvulsant + neuropathic analgesic (despite the name, no GABA activity).
Indications
- •Neuropathic pain
- •Multimodal perioperative analgesia (selectively — see caution)
- •Seizures (adjunct)
- •Restless legs
Dosing
| Context | Adult | Pediatric |
|---|---|---|
| Neuropathic pain | 300 mg PO, titrate to 900–3600 mg/day divided | — |
| Preop multimodal | 600 mg PO (institution-dependent — benefit debated) | — |
Pharmacokinetics
Onset ~1 h. RENALLY cleared (unchanged) → reduce in renal impairment. Saturable absorption (bioavailability falls at higher doses).
Side effects
- !Sedation, dizziness
- !Respiratory depression when COMBINED with opioids/CNS depressants (FDA warning — esp. elderly, renal, pulmonary disease)
- !Peripheral edema
Contraindications
- ×Abrupt withdrawal (seizure risk)
- ×Caution with opioids/elderly (sedation, respiratory depression)
Clinical pearls
- ★Routine preop gabapentinoids are now DISCOURAGED for general surgical populations (minimal opioid-sparing benefit, real sedation/respiratory-depression risk with opioids — 2022 guidelines).
- ★Renally cleared → accumulates in renal failure (excess sedation).
Other drugs in Narcotics & Analgesics
- Fentanyl
μ-opioid receptor agonist. ~100× potency of morphine.
- Remifentanil
μ-opioid agonist. Ester linkage hydrolyzed by nonspecific tissue + plasma esterases — no organ-dependent clearance.
- Morphine
μ-opioid receptor agonist. Active metabolite morphine-6-glucuronide (M6G) is analgesic and renally cleared — accumulates in renal failure → prolonged sedation/respiratory depression. Causes histamine release.
- Hydromorphone
μ-opioid agonist ~5–7× more potent than morphine. No clinically significant active metabolites → safer than morphine in renal failure. Less histamine release.
- Sufentanil
Most potent opioid in common clinical use — ~1000× morphine, ~10× fentanyl. High lipid solubility.
- Alfentanil
μ-opioid agonist ~1/5–1/10 the potency of fentanyl but FASTEST onset of the family — low pKa means a high non-ionized fraction at physiologic pH.
- Meperidine
μ-opioid agonist ~1/10 morphine, plus κ-agonism (anti-shivering). Active metabolite normeperidine is renally cleared, proconvulsant, and neurotoxic.
- Methadone
μ-opioid agonist with NMDA-receptor antagonism (blunts tolerance + opioid-induced hyperalgesia) and monoamine reuptake inhibition. Very long, variable half-life.
Browse all classes: /reference/drugs
Suggested reading
- •Stoelting & Hines, Pharmacology & Physiology in Anesthetic Practice, 6e
- •Miller's Anesthesia, 9e
- •FDA package insert
