Quantification of Losartan Potassium Polymorphs Using Powder X-Ray Diffraction.

Area of Science:

• Pharmaceutical Science
• Solid-State Chemistry
• Analytical Chemistry

Background:

• Losartan potassium, a widely used antihypertensive, exists in multiple polymorphic forms.
• Form I is the designated pharmaceutical crystal form, but can convert to Form III.
• Accurate quantification of these polymorphs is essential for drug quality control.

Purpose of the Study:

• To develop and validate a quantitative method for determining losartan potassium polymorphs.
• To establish a reliable analytical technique for distinguishing and measuring Form I and Form III.

Main Methods:

• Recrystallization was used to obtain pure Form I and Form III losartan potassium.
• Powder X-ray diffraction (PXRD) was the primary technique for characterization and quantification.
• Calibration curves were generated using characteristic peak area ratios and weight percentages.

Main Results:

• A linear calibration curve was established for the range of 1-50% (w/w).
• The method utilized the ratio of characteristic PXRD peak areas for Form I (11.13° 2θ) and Form III (5.64° 2θ).
• Excellent precision (0.6-4.9%) and a low limit of quantification (2.02% w/w) were achieved.

Conclusions:

• The developed PXRD method provides a quantitative analysis of losartan potassium polymorph mixtures (Forms I and III).
• This technique is suitable for controlling the quality of bulk losartan potassium.
• It represents a novel, consistent, sensitive, and accurate approach for quantifying Form III in losartan potassium samples.