Research ArticlesStabilization and HPLC Analysis of Betamethasone Sodium Phosphate in Plasma
Section snippets
INTRODUCTION
Administration of corticosteroids via the parenteral route for therapeutic purposes poses problems because of their limited aqueous solubility. To overcome this problem, corticosteroids have often been formulated as water-soluble hemisuccinate or phosphate ester prodrugs. These prodrugs are converted to the active steroid in vivo and the conversion is thought to occur rapidly and completely. Betamethasone (BET) in the form of its phosphate ester sodium salt is used in perinatal medicine.
Liquid Chromatography
The high-performance liquid chromatography (HPLC) system consists of a Waters model 510 pump, a Waters intelligent sample processor (model 717), and a model 486 Waters fixed wavelength UV detector (Waters Associates, Milford, MA). Analyte peaks are integrated using a Hewlett Packard (Avondale, PA) 3392A integrator. Separations are achieved using an Alltech Adsorbosphere HS (Alltech Associates, Inc., Deerfield, IL) C18 7 μm column (150 × 4.6 mm) attached to an Upchurch Scientific (Oak Harbor, WA)
Assay Characteristics and Validation
Published HPLC methods for measuring corticosteroids and their phosphate esters in plasma samples involve complex extraction procedures and utilize large sample volumes.3,7 Furthermore, determination of the prodrug requires either a second estimation step involving indirect estimation by hydrolysis to the steroid8 or a chromatographic method that makes use of highly acidic conditions to allow extraction and retention of the highly ionized phosphate prodrug.9 To circumvent these problems, an
Acknowledgements
The authors appreciate the provision of fresh blank sheep blood samples from the laboratory of Dr. Daniel Swartz of the University at Buffalo. This work was supported by grant GM24211 from the National Institutes of Health.
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