title: The determination of naproxen by spectrofluorometry and its binding to serum proteins.
abstract: A fluorometric method for the determination of naproxen in serum, albumin solutions and protein free buffer solutions is described. The detection limit is about 10 ng/ml. Furosemide, thiopental and salicylic acid did not show any disturbing fluorescence while phenprocoumon did. The in vitro binding of naproxen in albumin solutions and serum was studied by equilibrium dialysis. A small but significant increase was found in the percentual binding in albumin solutions as compared to serum. The percentual binding was not affected by changes in the pH from 5--8. By fitting the binding data to a model assuming two classes of binding sites, association constants and binding capacities were determined. A very high affinity and a high capacity were found. The association constant for the first class of binding sites was higher for human serum albumin than for serum (8.5 versus 5.3 . 10(6) M-1). The difference in the protein binding to the first class of binding sites in human serum albumin and serum can be explained by the existence of a competitive inhibitor in serum.
mesh_terms: D000418:Albumins; D001798:Blood Proteins / Q000378:metabolism*; D005665:Furosemide / Q000494:pharmacology; D006801:Humans; D009288:Naproxen / Q000032:analysis* / Q000097:blood; D010644:Phenprocoumon / Q000494:pharmacology; D011485:Protein Binding / Q000187:drug effects; D012980:Sodium Salicylate / Q000494:pharmacology; D013050:Spectrometry, Fluorescence / Q000379:methods*; D013874:Thiopental / Q000494:pharmacology
chemical_list: D000418:Albumins; D001798:Blood Proteins; D009288:Naproxen; D005665:Furosemide; D013874:Thiopental; D010644:Phenprocoumon; D012980:Sodium Salicylate