Adults

Dosage must be titrated. For postherpetic neuralgia, initial dose is 300 mg once daily on day 1, 300 mg twice daily on day 2, and 300 mg three times daily on day 3. For partial seizures, initial dose is often 300 mg three times daily, which may be initiated with lower doses like 50 mg, then titrated up. Individualize dose based on patient response and tolerability.

Elderly

Generally, lower initial doses and slower titration are recommended due to potential age-related decrease in renal function.

Renal_impairment

Dosage adjustment is necessary based on creatinine clearance. For CrCl >60 mL/min, standard dose; for CrCl 30-59 mL/min, reduce dose; for CrCl <30 mL/min, further reduce dose.

Onset

Varies by indication, generally within days to weeks for therapeutic effect.

Excretion

Excreted unchanged in the urine; primarily renally eliminated.

Half life

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

Absorption

Absorbed from the gastrointestinal tract, bioavailability is dose-dependent and decreases with increasing dose. Peak plasma concentrations reached within 2-3 hours.

Metabolism

Not appreciably metabolized in humans.

Opioids

Increased risk of respiratory depression, sedation, and coma. Use with caution, monitor closely, and consider dose reduction of either drug.

Antacids

May reduce gabapentin bioavailability. Take gabapentin at least 2 hours after antacids.

Hydrocodone

Reduces hydrocodone Cmax and AUC, increases gabapentin AUC.

Ethanol (Alcohol)

May enhance CNS depressant effects of gabapentin.