Development and Validation of Liquid Chromatography - Tandem Mass Spectrometry Method for the estimation of Potential Genotoxic Impurity 2-(2-Chloroethoxy)ethanol in Hydroxyzine

2-(2-Chloroethoxy)ethanol (CEE) belongs to the so-called cohort of concerns which were classified as a highly potent mutagenic carcinogen by the World Health Organization. CEE is widely used in the synthesis of essential anti-histamine drug hydroxyzine. Besides, it is used as primary solvent in the dyes, nitrocellulose, paints, inks and resins. Owing to its potential genotoxicity, an efficient liquid chromatography-tandem mass spectrometry method was developed for the quantitative estimation of CEE traces in an active pharmaceutical ingredient and in tablet dosage forms of hydroxyzine-free base. The chromatographic separation was achieved on C₁₈ column using a gradient elution mode with a binary solvent system (ammonium formate and methanol). Mass detection was performed for the CEE using a positive mode with selected ion monitoring technique at m/z value of [M+NH₄ ]⁺ . The developed method was validated as per the ICH guideline, the quantitation limit, linearity and recoveries were found to be 0.56 ppm, 0.56 ~ 7.49 ppm (r² > 0.9985) and 93.6 ~ 99.3%, respectively. The proposed method was highly compatible and was worked effectively to estimate the CEE traces in different stages of drug synthesis and in tablet dosage forms of hydroxyzine for the routine and stability testing.

Overall impact of the regulatory requirements for genotoxic impurities on the drug development process

In the last decade a considerable effort has been made both by the regulators and the pharmaceutical industry to assess genotoxic impurities (GTI) in pharmaceutical products. Though the control of impurities in drug substances and products is a well established and consolidated procedure, its extension to GTI has given rise to a number of problems, both in terms of setting the limits and detecting these impurities in pharmaceutical products. Several papers have dealt with this issue, discussing available regulations, providing strategies to evaluate the genotoxic potential of chemical substances, and trying to address the analytical challenge of detecting GTI at trace levels. In this review we would like to discuss the available regulations, the toxicological background for establishing limits, as well as the analytical approaches used for GTI assessment. The final aim is that of providing a complete overview of the topic with updated available information, to address the overall GTI issue during the development of new drug substances.

Reichardt's dye and its reactions with the alkylating agents 4-chloro-1-butanol, ethyl methanesulfonate, 1-bromobutane and Fast Red B - a potentially useful reagent for the detection of genotoxic impurities in pharmaceuticals

Objectives

Alkylating agents are potentially genotoxic impurities that may be present in drug products. These impurities occur in pharmaceuticals as by-products from the synthetic steps involved in drug production, as impurities in starting materials or from in-situ reactions that take place in the final drug product. Currently, analysis for genotoxic impurities is typically carried out using either HPLC/MS or GC/MS. These techniques require specialist expertise, have long analysis times and often use sample clean-up procedures. Reichardt's dye is well known for its solvatochromic properties. In this paper the dye's ability to undergo alkylation is reported.

Methods

The reaction between Reichardt's dye and alkylating agents such as 4-chloro-1-butanol and ethyl methanesulfonate was monitored spectrophotometrically at 618 nm in acetonitrile and 624 nm in N,N-dimethylformamide.

Key findings

Changes in absorption were observed using low levels of alkylating agent (5–10 parts per million). Alkylation of the dye with 4-chloro-1-butanol and ethyl methanesulfonate was confirmed. Reichardt's dye, and its changing UV absorption, was examined in the presence of paracetamol (10 and 100 mg/ml). Whilst the alkylation-induced changes in UV absorption were not as pronounced as with standard solutions, detection of alkylation was still possible.

Conclusions

Using standard solutions and in the presence of a drug matrix, Reichardt's dye shows promise as a reagent for detection of low levels of industrially important alkylating agents.

Residues of genotoxic alkyl mesylates in mesylate salt drug substances: Real or imaginary problems?

Mesylate esters of short-chain (n = 1-3) alcohols are reactive, direct-acting, genotoxic and possibly carcinogenic alkylating agents. Their chemical and biological properties appear to correlate well with Swain-Scott s constants; for example, high S(N)1 character (low s value) is associated with enhanced carcinogenic potential, but also a rapid hydrolysis rate. Concerns over the possible formation of such esters during the preparation of mesylate salt drug substances, by addition of methane sulfonic acid (MSA) to the free base dissolved in an alcoholic solvent, have led regulatory agencies to require applicants to demonstrate that the synthetic method employed does not lead to the presence of detectable levels of alkyl mesylates. Mechanistic considerations, relating mainly to the extremely low nucleophilicity of the mesylate anion, and experimental data, both indicate that alkyl mesylates should not be formed (except from MSA impurities) during mesylate salt synthesis. Mechanistic arguments also predict that residues of alkyl halides (possibly formed in the preparation of amine hydrochlorides or hydrobromides) could represent a similar or greater potential hazard than alkyl mesylates. The perceived risk of alkyl mesylate formation seems to rely on mistaken assumptions and so the concerns appear unjustified. Further reassurance could be achieved however by applying a variety of strategies during synthesis, including pH control, and use of high-purity MSA or of a non-hydroxylic reaction solvent.