# Developing a Chromatographic Method for Quantifying Latanoprost and Related Substances in Glaucoma Treatments

## TL;DR

This paper presents a new chromatographic method to accurately measure latanoprost and related substances in glaucoma treatments, improving drug safety and efficacy.

## Contribution

A novel, validated chromatographic method for simultaneous quantification of latanoprost and six related substances in eye drops.

## Key findings

- The method is linear for latanoprost in the range of 40–60 µg/mL and for related substances in 0.05–2.77 µg/mL.
- Recoveries for latanoprost were within 98.0–102.0% for assays and 90.0–110.0% for impurities.
- The method's stability-indicating power was confirmed through forced degradation studies.

## Abstract

Background/Objectives: Latanoprost is a leading active pharmaceutical ingredient belonging to the synthetic prostaglandin F2α analogs, widely used as a first-line treatment for open-angle glaucoma and increased intraocular pressure. This study addresses the critical need for an accurate and precise chromatographic method that is capable of simultaneously quantifying latanoprost and six latanoprost-related substances in antiglaucoma eye drops. This will be crucial for patient safety and treatment efficacy. This method enables the separation of latanoprost isomers, (15S)-latanoprost, latanoprost enantiomer, and 5,6-trans latanoprost from latanoprost signal. Furthermore, it is specific for the well-known latanoprost degradants—the major latanoprost acid and the minor 15-ketolatanoprost—as well as synthetic derivatives, such as triphenylphosphine oxide (TPPO) and propan-2-yl 5-(diphenylphosphoryl)pentanoate (IDPP). Using forced degradation studies using high temperatures, UV light, alkalis, acids, and oxidizing agents, the degradation profiles of the drugs were characterized and the method’s stability-indicating power was confirmed. Methods: Separation was achieved on a stationary combined system comprising chiral and cyano columns. Reverse-phase gradient elution and UV 210 nm detection were employed. The novel method was validated according to the European Medicines Agency International Council for Harmonisation Q2 Validation of analytical procedures—Scientific guideline. Results: The method was shown to be linear in the range of 40–60 µg/mL for latanoprost and 0.05–2.77 µg/mL for related substances, confirmed by a correlation coefficient of r = 0.999. Recoveries for latanoprost were obtained within the range of 98.0–102.0% for assays and 90.0–110.0% for impurities. The detection and quantification limits for latanoprost were 0.025 µg/mL and 0.35 µg/mL, respectively. Conclusions: The analytical procedure developed is adequately sensitive, precise, and accurate compared to existing methods. The method can be reliably used to control the critical quality attributes of low-dose latanoprost products, ensuring their required high pharmaceutical quality, which translates into improvements in patient care. This advancement holds significant implications for enhancing the therapeutic management of glaucoma, ensuring drug safety and efficacy.