Development of spironolactone oral suspension for pediatric use and chemicophysical stability study using capillary electrophoresis and HPLC

Introduction
Spironolactone (SPI) is used to treat childrens’ heart failure and fluid retention. The aim of this study was to make an oral formulation suitable for pediatric patients. Inorpha^®, a ready-to-use suspension vehicle was chosen after bibliographic review. Difficulty of resuspending SPI in Inorpha^® is described in related literature. The formulation was adapted by adding xanthan gum (XG).
The aim was to improve the formulation and to study its stability by capillary electrophoresis (CE) and HPLC.

Materials and Methods
Stability indicating methods were developed and validated by Micellar Electrokinetic Chromatography (MEKC) and High-Performance Liquid Chromatography (HPLC). Detection limits of both methods were investigated.
A forced sedimentation test (3000 rpm for 3 min (n = 3)) simulating sedimentation over time was performed with increasing concentrations of XG (0, 0.10, and 0.25%) to determine the quantity of XG to be added to Inorpha^®. Two batches of SPI suspension in Inorpha^® with 0.25% XG were prepared and stored refrigerated in 30 mL amber glass bottles. Stability study was performed over six months. SPI concentration, pH and osmolality were determined.

Results
Forced sedimentation test showed that after homogenization (20 inversions), SPI analysis of the floating sample without XG showed a level of 59% of the initial concentration, compared to 85% with 0.10% XG and 102% with 0.25% XG.
For the stability indicating methods, SPI formulation was exposed to NaOH 0.025 M for 15 min at room temperature, H2O2 10% for 60 min at 80°C, HCl 1 M for 30 min at 80°C.
Comparable results for SPI degradation products were obtained under acidic and basic conditions by HPLC and EC: canrenone and 7-α-thio-SPI were detected. Unlike the EC, HPLC did not detect degradation product resulting from oxidation.
Peak purity was checked for both methods. The detection limits for SPI by EC and HPLC were 1 µg/mL and 0.025 µg/mL.
The mean concentration of SPI between Day0 and Day180 varied between 98.9% and 101.7% of the initial concentration without degradation products. The pH remained stable at 4.9 ± 0.1, as did the osmolality at 209 ± 26 mOsm/kg.

Conclusion
A suitable formulation of SPI in Inorpha® with 0.25% XG was developed for pediatric use. The chemicophysical stability was demonstrated for 6 months. CE allows to detect all degradation products but detection limit is higher than HPLC. Microbiological stability is highly recommended as the expiration date depends on the manufacturing conditions

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