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Effects of Age and Gender on Single‐Dose Pharmacokinetics of Gabapentin
Author(s) -
Boyd Rebecca A.,
Türck Dietrich,
Abel Robert B.,
Sedman Allen J.,
Bockbrader Howard N.
Publication year - 1999
Publication title -
epilepsia
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.687
H-Index - 191
eISSN - 1528-1167
pISSN - 0013-9580
DOI - 10.1111/j.1528-1157.1999.tb00743.x
Subject(s) - pharmacokinetics , gabapentin , medicine , clinical neurology , pharmacology , psychology , neuroscience , pathology , alternative medicine
Summary:Purpose: This study was conducted to evaluate the effect of age, age‐related changes in renal function, and gender on the single‐dose pharmacokinetics of orally administered gabapentin (GBP). Methods: The pharmacokinetics of a single 400‐mg oral dose of GBP were studied in 36 healthy subjects (18 men and 18 women) aged 20–78 years. Serial blood samples and total urine output were collected for 48 h after the dose. GBP concentrations in plasma and urine were measured by high‐performance liquid chromatography, and pharmacokinetic parameters were calculated by noncompartmental methods. Results: All subjects tolerated the drug well, with only mild symptoms reported. No change in maximal GBP plasma concentration (C max ), time at which C max occurred (t max ), or apparent volume of distribution (V/F) with age was noted. A significant linear decline in apparent oral clearance (CL/F), elimination‐rate constant (λ z ), and renal clearance (CL R ) with increasing age was observed (p < 0.005). Because total urinary recovery of unchanged drug (an estimate of F for GBP) did not change with age, the decline in CL/F and λ z can be explained by the decline in CL R . The only pharmacokinetic parameter that was significantly different between genders was C max , which was −25% higher for women than for men (p = 0.016), consistent with gender differences in body size. Conclusions: The results of this study suggest that changes in renal function are responsible for age‐related changes in GBP pharmacokinetics. Reduction of GBP dosage may be required in elderly patients with reduced renal function. The pharmacokinetics of GBP are similar in men and women.