Influence of tube type, storage time, and temperature on the total and free concentration of XXXX .

@entity4958 @entity1092 @entity1372 @entity2052 @entity1098
The influence of storage conditions on the total and free concentration of @entity1092 ( @entity2052 ) was studied in six normal male subjects who ingested 750 mg of @entity2052 (3 X 250 mg @entity1092 capsules; Abbott Laboratories). Blood samples were collected in various types of Vacutainer tubes (red top, no additives; green top, @entity1372 heparin; blue top, @entity4958 ; and purple top, @entity1098 ) 2 h post administration of @entity2052 . Either these samples were centrifuged immediately or stored for various periods of time at room temperature or refrigerated, or the supernate was frozen prior to analysis. Free @entity2052 samples were obtained utilizing the Amicon ultrafiltration system. All @entity2052 samples were analyzed by gas-liquid chromatography. Total @entity2052 concentrations obtained from plasma collected with @entity4958 were lower (p less than 0.05) than either serum or plasma collected with other anticoagulants. There were no differences (p greater than 0.05) in total or free @entity2052 concentrations between samples collected in serum or in plasma collected with heparin or @entity1098 . Storing samples for 96 h at room temperature did not alter the total @entity2052 concentrations but was found to increase the free fraction of @entity2052 (p less than 0.05). The refrigeration or freezing of the supernate from the blood samples for 7 days did not alter (p greater than 0.05) the total or the free fraction of @entity2052 . The results of this study demonstrate that total and/or free @entity2052 may be collected from either serum or plasma, provided @entity4958 is not used to collect plasma.(ABSTRACT TRUNCATED AT 250 WORDS)
