Adults

For epilepsy: Initial dose 300 mg three times daily (TID) on Day 1, then titrated up to 900-3600 mg/day in 3 divided doses. For neuropathic pain: Initial 300 mg on Day 1, then titrated up to 1800-3600 mg/day in 3 divided doses.

Elderly

Start with a lower dose (e.g., 100 mg TID) and titrate slowly, monitoring for adverse effects and adjusting for renal function.

Renal_impairment

Dose adjustment required based on creatinine clearance (CrCl). For CrCl < 30 mL/min, significant dose reduction is needed. Hemodialysis patients require supplemental doses.

Onset

Onset of effect varies, typically within days to weeks for full therapeutic benefit.

Excretion

Primarily excreted unchanged by the kidneys. Renal impairment significantly prolongs half-life.

Half life

Approximately 5 to 7 hours in adults with normal renal function.

Absorption

Oral bioavailability is not dose-proportional; it decreases with increasing dose due to saturable absorption.

Metabolism

Not significantly metabolized in humans; it does not induce or inhibit hepatic enzymes.

Ethanol/Alcohol

May potentiate the sedative effects of gabapentin.

Opioids (e.g., Morphine)

Concurrent use may increase gabapentin concentrations and increase the risk of CNS depression. Monitor for sedation and respiratory depression.

Antacids (e.g., aluminum and magnesium containing)

May reduce the bioavailability of gabapentin. Administer gabapentin at least 2 hours after antacid administration.