Adults

Initial dose 300 mg orally on Day 1, then 300 mg twice daily on Day 2, and 300 mg three times daily on Day 3. Dosage may be titrated up to 1800-3600 mg/day in divided doses.

Elderly

Dose adjustment may be necessary in elderly patients due to age-related decrease in renal function.

Renal_impairment

Dose adjustment required based on creatinine clearance. For CrCl 30-59 mL/min, maximum 900 mg/day; for CrCl 15-29 mL/min, maximum 600 mg/day; for CrCl <15 mL/min, maximum 300 mg/day.

Onset

Therapeutic effects may be observed within hours to days, depending on the indication and titration.

Excretion

Excreted unchanged primarily by the kidneys.

Half life

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

Absorption

Oral absorption is dose-dependent and saturable, decreasing with increasing dose. Bioavailability ranges from 27% to 60%.

Metabolism

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

Ethanol

May potentiate CNS depressant effects of Gabapentin.

Antacids

Concurrent use of antacids containing aluminum and magnesium can reduce the bioavailability of Gabapentin. Administer Gabapentin at least 2 hours after antacid administration.

Cimetidine

May slightly decrease the renal excretion of Gabapentin, but is generally not clinically significant.

Opioids (e.g., Morphine)

May increase Gabapentin levels and enhance central nervous system (CNS) depression, including sedation and respiratory depression. Monitor patients closely and reduce Gabapentin dose if necessary.