Studies On Enantiomeric Separation And Pharmacokinetics Of Bicalutamide

Bicalutamide is a non-steroidal anti-androgen which has the brand name Casodex of AstraZeneca. It is a chiral compound having one asymmetric carbon, which can exist as (R)- or (S)- enantiomer. The properties of bicalutamide as an anti-androgen agent and its usefulness in treating prostate cancer have been reviewed, and the (R)-enantiomer, the dextrorotatory isomer, has been revealed to be more active than the (S)-enantiomer in in vivo and ex vivo studies. Because of the two enantiomer activities in vivo are different, so the enantiomeric separation of racemic bicalutamide and pharmacokinetica of enantiomer are particularly impartant. In this study, A normal-phase high performance liquid chromatography (NP-HPLC) method was established for the enantiomeric separation of racemic bicalutamide; the NP-HPLC method for the quantification of bicalutamide enatiomers in rat plasma was developed; and the pharmacokinetcics of bicalutamide enatiomers was investigated. The modification of the ultrafiltration technique was used to overcome solubility and non-specific binding challenges associated with the measurement of plasma protein binding of bicalutamid. This dissertation is divided into three sections:1. A normal-phase high performance liquid chromatography (NP-HPLC) method was established for the enantiomeric separation of racemic bicalutamide. Effects of column types, isopropanol modifier concentration, flow rate and temperature on the enantiomeric separation were investigated. A Chiralpak AD-H column was used with the mobile phase of hexane-isopropanol (70︰30) solution at the detection wavelength of 270 nm. The flow rate was 0.6 ml/min and the temperature of column was 20℃. A base-line separation of bicalutamide enantiomers was achieved on the Chiralpak AD-H column. The resolution was 7.0.2. A NP-HPLC method was established for the determination of bicalutamide enantiomers in rat plasma. The plasma samples were deproteinized with acetone in a one-step extraction. The HPLC assay was carried out using a Chiralpak IC enantiomeic column and the mobile phase consisting of hexane-isopropanol (77︰23)was used at a flow rate of 0.8 mL min^-1 for the effective eluting bicalutamide enantiomers. The detection of the analyte peak area was conducted by setting a UV detector at 270 nm with no interfering plasma peak. The temperature of column was 30℃. The method was fully validated and the result showed that the method has the merit of sensitiveness, accuracy and convenience, and satisfies the need of pharmaceutical analysis in vivo. The method was further used to determine the concentration-time profiles of bicalutamid in the rat plasma following intravaneous injection. Elimination of (S)-bicalutamide was much faster than those of (R)-bicalutamide.3. The measurement of plasma protein binding of bicalutamide by using the ultrafiltration technique was also investigated. Bicalutamid has poor solubility, so that non-specific binding (NSB) was higher with the conventional ultrafiltration technique. Taylor developed a modification of ultrafiltration technique to overcome solubility and non-specific binding challenges associated with the measurement of plasma protein binding. Some factors were studied, such as solubility of bicalutamide in PBS buffer, the influence of PBS on the mobile phae of NPLC, etc. At last, by using Taylor's method, rat plasma protein binding of racemic bicalutamide was about 80%, and rat plasma protein binding of (R)-bicalutamide was higher than that of those of (R)-bicalutamide...