Development and validation capillary electrophoresis method for the determination of spironolactone in a new 5 mg/mL oral formulation

Spironolactone (SPI) is administered to children for primary hyperaldosteronism, edema and heart failure. The goal is to provide an orally administered suspension to address the lack of a pediatric formulation. A prior literature review led to the selection of Inopha^® as the suspension vehicle. However, due to the challenge of resuspending SPI, a formulation with the addition of 0.25 % xanthan gum (GX) was employed.The aim was to develop and validate a capillary electrophoresis (CE) method for quantifying spironolactone.

Materials/Method
Considering SPI’s neutral pKa value, the micellar electrokinetic chromatography (MEKC) mode of CE has been implemented. The objective was to separate SPI from its degradation product canrenone (CAN). Optimization of the method (e.g., resolution Rs, analysis time) was achieved by varying the concentrations of sodium dodecyl sulfate (SDS), borate, organic solvents (methanol, acetonitrile), and pH in the electrolyte solution. The effective capillary length was 56 cm. Detection was performed via UV. An internal standard, hydrocortisone (100µl/ml), was employed.
Method validation followed the SFTP guidelines establishing accuracy profiles at three concentrations (70, 100 and 130 µg/mL) with acceptability limits set at +/- 10 % and proportion β of 95%. The limit of detection (LOD) for SPI and CAN was determined.

Results
Optimal conditions for the electrophoretic buffer were acheived with 25 mM SDS in 50 mM borate/methanol (85/15) mixture at pH 9.0. Other analytical conditions included an applied voltage of 30 kV, regulated temperature of 25°C and an injection pressure of 50 mBar for 6 seconds. The selected wavelenght for SPI quantification was 242 nm. Under these conditions, SPI and CAN were separated in 18 min with an Rs of 4.78.
The obtained results gave an accuracy profile in line with the limits set, with recovery ranging from 101.5 (and) to 104.3%. Repeatability coefficients of variation ranged from 1.1 to1.8% and for reproducibility from 1.9 to 2.4%. The limit of detection for SPI was 1 µg/mL and for CAN 0.5 µg/mL.

Discussion / Conclusion
The use of a MEKC method allows the determination of SPI. This method, provides an alternative to HPLC for the release of hospital preparations.
The method’s performance appears suitable for conducting a stability of SPI in Inorpha^® enriched with 0.25% GX.