Stability Determination of an Extemporaneously Compounded Ambrisentan Suspension by High Performance Liquid Chromatography Analysis

OBJECTIVE

Ambrisentan, an endothelin receptor antagonist FDA-approved for the treatment of pulmonary arterial hypertension in adult patients, lacks an acceptable pediatric dosage form. The objective of this investigation was to determine the stability of an extemporaneously compounded ambrisentan suspension.

METHODS

Ambrisentan suspension was compounded to a concentration of 1 mg/mL using commercially available suspending agents. The suspension was then evenly split into 2 plastic amber prescription bottles. One bottle was stored at room temperature and under continuous fluorescent light while the other bottle was stored under refrigeration and protection from light. A fast and selective reversed-phase high-performance liquid chromatography (HPLC) method was developed and validated for the analysis of ambrisentan. HPLC analysis was performed on samples withdrawn from the stock bottles at predetermined time intervals, up to 90 days.

RESULTS

The developed HPLC method enabled the elution and detection of ambrisentan peak at 4.4 minutes. HPLC analysis revealed that all samples from both storage conditions retained >90% potency throughout the study timeframe. There were no signs of any ambrisentan breakdown products on HPLC analysis. Color and odor of the final product was also consistent throughout the 90-day storage period.

CONCLUSION

Ambrisentan suspension, compounded to 1 mg/mL, is stable at room temperature or under refrigeration for up to 90 days.

Stability-indicating UPLC-PDA Method for Ambrisentan Tablets and Identification of a Main Degradation Product by UPLC-MS/MS

Background:

Ambrisentan is a drug used to treat the pulmonary arterial hypertension symptoms, commercialized as coated tablets. Drug quality control is an essential part for the development and release of drugs for consumption; however, there are few studies related to the proposition of analytical methods and stability study for ambrisentan.

Objective:

The development of an UPLC assay of ambrisentan in tablets with degradation product`s elucidation was proposed.

Methods:

Tests with different solvents and chromatographic columns were carried out, achieving an optimal condition using mobile phase in gradient mode, Waters® BEH C18 column and detection at 260 nm.

Results:

Satisfactory system suitability was obtained (theoretical plates, sensitivity and resolution among peaks), with a reduced analysis time (6 minutes). The method was validated in accordance with the international guidelines and it demonstrated adequate specificity, either for the drug assay as for the identification and quantification of degradation product. It showed linearity (r= 0.999), accuracy (degradation products recovery: 98.47 - 102.44; assay recovery: 99.98 - 104.32%) and precision (RSD: 0.69), with limits of quantification and detection in suitable magnitude in order to evaluate possible drug degradation.

Conclusion:

UPLC method demonstrated to be fast with satisfactory robustness. The main ambrisentan degradation product formed under thermal stress conditions was elucidated by UPLC-MS/MS and its structure was suggested.

Enantioseparation and impurity determination of ambrisentan using cyclodextrin-modified micellar electrokinetic chromatography: Visualizing the design space within quality by design framework

A capillary electrophoresis method for the simultaneous determination of the enantiomeric purity and of impurities of the chiral drug ambrisentan has been developed following the Quality by Design principles. The selected separation system consisted of a micellar pseudostationary phase made by sodium dodecyl sulphate with the addition of γ-cyclodextrin. The effects of critical process parameters (capillary length, temperature, voltage, borate concentration, pH, sodium dodecyl sulphate concentration, γ-cyclodextrin concentration) on enantioresolution of ambrisentan and analysis time were extensively investigated by multivariate strategies involving a screening phase and Response Surface Methodology. The Design Space was defined with a desired probability level π≥90%, and the working conditions, with the limits of the Design Space, corresponded to the following: capillary length, 64.5cm; temperature, 22°C; voltage, 30kV (26-30kV); background electrolyte, 100mM borate buffer pH 9.20 (8.80-9.60), 100mM sodium dodecyl sulphate, 50mM (43-50mM) γ-cyclodextrin. A Plackett-Burman design was applied for robustness testing, and a method control strategy was established. The method was fully validated according to the International Conference on Harmonisation guidelines and was applied to ambrisentan coated tablets.