Modernization of USP Monographs for Naphazoline Hydrochloride and Pheniramine Maleate Ophthalmic and Nasal Solutions

Importance of the Topic

An accurate and robust analytical method for combined assay of naphazoline hydrochloride and pheniramine maleate in ophthalmic and nasal formulations is critical for quality control and regulatory compliance. Modernizing these USP monographs ensures specificity in impurity testing, improved peak symmetry, and supports patient safety by guaranteeing consistent drug potency and purity.

Study Objectives and Overview

This work aimed to update three USP monographs for:

• Naphazoline HCl nasal solution
• Naphazoline HCl ophthalmic solution
• Combined pheniramine maleate/naphazoline HCl ophthalmic solution

A single liquid chromatography method was developed to quantify active pharmaceutical ingredients (APIs) and resolve their related substances in one run, reducing analysis time and simplifying workflows.

Methodology and Instrumentation

Sample Preparation:

• Stock solutions prepared in a 90:10 water/acetonitrile diluent (mobile phase A/mobile phase B).
• Resolution mixture: 100 µg/mL of each API and related compound.
• Working standard: 500 µg/mL pheniramine maleate and 40 µg/mL naphazoline HCl.

Chromatographic Conditions:

• Column: XSelect CSH C18 (4.6×150 mm, 5 μm).
• Mobile phases: A – 0.05% triethylamine and 0.05% phosphoric acid in water; B – 0.05% phosphoric acid in acetonitrile.
• Gradient elution at 2.0 mL/min, column temperature 40 °C, injection volume 8 μL.
• Detection: PDA at 280 nm; mass detection with ACQUITY QDa, ESI+ and ESI–, 100–250 Da.

System Suitability and Linearity:

• Five replicates of working standard showed repeatable retention times and peak areas.
• Linearity assessed between 80–120% of nominal concentrations with R² >0.999 for both APIs.

Instrument Used

ACQUITY Arc UPLC with photodiode array (PDA) detector and ACQUITY QDa mass detector. This setup enabled simultaneous UV and MS detection for compound identification and spectral purity assessment.

Main Results and Discussion

The optimized method achieved resolution >2.2 between APIs and their related substances. Addition of 0.05% triethylamine reduced pheniramine peak tailing from 2.2 to 1.5 by minimizing secondary interactions. Signal-to-noise ratios at 0.1% impurity level exceeded 30 for all related compounds, confirming method sensitivity. Analysis of commercial ophthalmic and nasal products delivered recovery values between 95% and 105%, within USP assay limits.

Benefits and Practical Applications

This single-run LC method offers:

• Efficient simultaneous analysis of two APIs and multiple impurities.
• Improved peak shape and separation, enhancing specificity.
• Reduced solvent consumption and shorter analysis time compared to separate assays.
• Mass detection for rapid compound confirmation.

The method streamlines quality control for manufacturers of eye-drop and nasal formulations, supporting compliance with compendial standards.

Future Trends and Potential Applications

Advancements may include coupling to high-resolution mass spectrometry for trace-level impurity profiling and hyphenation with automated sample prep for higher throughput. Expansion to other dual-API ophthalmic/nasal combinations will further leverage this platform approach for monograph modernization across drug classes.

Conclusion

A unified LC-UV-MS method was successfully developed and validated to modernize three USP monographs for naphazoline HCl and pheniramine maleate formulations. The approach enhances specificity, sensitivity, and productivity in routine quality control.

Reference

1. USP Monograph, Naphazoline Hydrochloride Nasal Solution, USP40-NF35, The United States Pharmacopeia Convention, December 2017.
2. USP Monograph, Naphazoline Hydrochloride Ophthalmic Solution, USP40-NF35, The United States Pharmacopeia Convention, December 2017.
3. USP Monograph, Naphazoline Hydrochloride and Pheniramine Maleate Ophthalmic Solution, USP40-NF35, The United States Pharmacopeia Convention, December 2017.