Age- and dose-dependent naproxen disposition in Fischer 344 rats. 1991

J H Satterwhite, and F D Boudinot
College of Pharmacy, University of Georgia, Athens.

The effects of age and dose on the pharmacokinetics of naproxen were evaluated in young and senescent male Fischer 344 rats after 2.5 and 25 mg/kg doses. Pharmacokinetic parameters based on free naproxen concentrations demonstrated a significant decrease in free clearance and free steady-state volume of distribution in the aged rats. In vitro enzyme kinetic studies also demonstrated an age-related decline in the metabolic activity and affinity of the metabolic enzymes for naproxen in the aged rats. Plasma protein binding studies revealed a larger free fraction of drug in the plasma of senescent rats. Total clearance and steady-state volume of distribution were indistinguishable between young and old rats owing to the higher free fraction in aged rats. Dose had a significant effect with free clearance and free volume of distribution decreasing as dose increased. The binding of naproxen to plasma proteins was dependent on drug concentration. Unlike the parameters based on free naproxen concentrations, total plasma clearance and volume of distribution increased with increasing dose, due to the nonlinear protein binding.

UI MeSH Term Description Entries
D007275 Injections, Intravenous Injections made into a vein for therapeutic or experimental purposes. Intravenous Injections,Injection, Intravenous,Intravenous Injection
D008099 Liver A large lobed glandular organ in the abdomen of vertebrates that is responsible for detoxification, metabolism, synthesis and storage of various substances. Livers
D008297 Male Males
D008862 Microsomes, Liver Closed vesicles of fragmented endoplasmic reticulum created when liver cells or tissue are disrupted by homogenization. They may be smooth or rough. Liver Microsomes,Liver Microsome,Microsome, Liver
D009288 Naproxen An anti-inflammatory agent with analgesic and antipyretic properties. Both the acid and its sodium salt are used in the treatment of rheumatoid arthritis and other rheumatic or musculoskeletal disorders, dysmenorrhea, and acute gout. Aleve,Anaprox,Methoxypropiocin,Naprosin,Naprosyn,Naproxen Sodium,Proxen,Sodium Naproxenate,Synflex,Naproxenate, Sodium,Sodium, Naproxen
D009929 Organ Size The measurement of an organ in volume, mass, or heaviness. Organ Volume,Organ Weight,Size, Organ,Weight, Organ
D011485 Protein Binding The process in which substances, either endogenous or exogenous, bind to proteins, peptides, enzymes, protein precursors, or allied compounds. Specific protein-binding measures are often used as assays in diagnostic assessments. Plasma Protein Binding Capacity,Binding, Protein
D011506 Proteins Linear POLYPEPTIDES that are synthesized on RIBOSOMES and may be further modified, crosslinked, cleaved, or assembled into complex proteins with several subunits. The specific sequence of AMINO ACIDS determines the shape the polypeptide will take, during PROTEIN FOLDING, and the function of the protein. Gene Products, Protein,Gene Proteins,Protein,Protein Gene Products,Proteins, Gene
D011916 Rats, Inbred F344 An inbred strain of rat that is used for general BIOMEDICAL RESEARCH purposes. Fischer Rats,Rats, Inbred CDF,Rats, Inbred Fischer 344,Rats, F344,Rats, Inbred Fisher 344,CDF Rat, Inbred,CDF Rats, Inbred,F344 Rat,F344 Rat, Inbred,F344 Rats,F344 Rats, Inbred,Inbred CDF Rat,Inbred CDF Rats,Inbred F344 Rat,Inbred F344 Rats,Rat, F344,Rat, Inbred CDF,Rat, Inbred F344,Rats, Fischer
D002851 Chromatography, High Pressure Liquid Liquid chromatographic techniques which feature high inlet pressures, high sensitivity, and high speed. Chromatography, High Performance Liquid,Chromatography, High Speed Liquid,Chromatography, Liquid, High Pressure,HPLC,High Performance Liquid Chromatography,High-Performance Liquid Chromatography,UPLC,Ultra Performance Liquid Chromatography,Chromatography, High-Performance Liquid,High-Performance Liquid Chromatographies,Liquid Chromatography, High-Performance

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