The importance of impurity analysis in pharmaceutical products: an integrated approach

To purify a material and remove the excess impurities one should first recognize that whether they are actually present and what their nature is. In the past, this was not always done. But presently drug analysis and pharmaceutical impurities are the subjects of constant review in the public interest. The International Conference on Harmonisation (ICH) guidelines achieved a great deal in harmonizing the definitions of the impurities in new drug substances. It is necessary to perform all the investigations on appropriate reference standards of drug and impurities to get meaningful specifications. In order to meet the challenges to ensure high degree of purity of drug substances and drug products, a scheme is proposed for profiling drug impurity. Finally, analytical methods based on analytical instrumentation must be employed to quantitate drug substance and its impurities. Important aspects and suggestions related to drug analysis and pharmaceutical impurities are discussed.     

Synthesis and characterization of critical process related impurities of an asthma drug – Zafirlukast

Zafirlukast is an oral leukotriene receptor antagonist (LTRA) for the treatment of pulmonary disorders such as asthma. During the process development of zafirlukast, eight process related impurities were observed at a level of 0.1–0.15 area percent. Synthesis and characterization of these impurities and investigation of the root cause of their formation is described.     

Modelling oligomer formation in chromatographic separations

Oligomer forms of proteins are formed by self and cross association or complex formation with ligands. Modelling studies using an ion-exchange adsorbent have demonstrated that the formation of an oligomer form of a target protein can improve a chromatographic separation because the oligomer form displaces the impurities. The results of the investigation show that the process is very robust, that the purity, the yield, and the productivity increase with increasing load and increasing salt concentration in the eluant. An impurity level less than 1 ppm is easy to achieve having a yield of 98%. A universal model for the adsorption equilibria of mono and oligomer forms of proteins on ion-exchange, hydrophobic, and bimodal adsorbents has been developed.     

盐酸二甲双胍药物中杂质测定方法研究进展

摘要：对近年来盐酸二甲双胍类药物中杂质的测定方法进行综述。盐酸二甲双胍类药物中的杂质主要有双氰胺、二甲胺以及由二甲胺形成的亚硝胺类基因毒性杂质等。测定方法主要有高效液相色谱（HPLC）法、离子色谱（IC）法、高效液相色谱-串联质谱（HPLC-MS/MS）法和气相色谱-串联质谱（GC-MS/MS）法,其中高效液相色谱法主要用于测定双氰胺,衍生化-高效液相色谱法和离子色谱法主要用于测定二甲胺,HPLC-MS/MS法和GC-MS/MS法主要用于测定亚硝胺类基因毒性杂质。该综述旨在为盐酸二甲双胍类药物中杂质的测定提供参考。     

Development and validation of an HPLC method for the determination of process-related impurities in pridinol mesylate, employing experimental designs

A simple high performance liquid chromatographic method for the determination of process-related impurities in bulk drug of the central anticholinergic compound pridinol mesylate, has been developed and validated. Spectroscopically characterized synthetic impurities were used as standards. The chromatographic separation was optimized employing an experimental design strategy, and was achieved on a C₁₈ column with a mobile phase containing 50 mM potassium phosphate buffer (pH 6.4), MeOH and 2-propanol (20:69:11, v/v/v), delivered at a flow rate of 1.0 mL min⁻¹. UV detection was performed at 245 nm. The optimized method was thoroughly validated, demonstrating to be selective, when the chromatogram was recorded with a diode-array detector and peak purities were evaluated (>0.9995). The method is robust and linear (r² > 0.99) over the range 0.05-2.5% (5-250% with regards to the 1% specification limit for both process-related impurities); it is also precise, regarding repeatability (RSD ≤ 1.5% for all of the analytes) and intermediate precision aspects and LOQ values for the impurities are below 0.01%. Method accuracy, evidenced by low bias of the results and analyte recoveries in the range of 99.1-102.7%, was assessed at five analyte concentration levels. The usefulness of the determination was also demonstrated through the analysis of different lots of pridinol mesylate bulk substance. The results indicate that the method is suitable for the quality control of the bulk manufacturing of pridinol mesylate drug substance.     

Near infrared and Raman spectroscopy as Process Analytical Technology tools for the manufacturing of silicone-based drug reservoirs

Using near infrared (NIR) and Raman spectroscopy as PAT tools, 3 critical quality attributes of a silicone-based drug reservoir were studied. First, the Active Pharmaceutical Ingredient (API) homogeneity in the reservoir was evaluated using Raman spectroscopy (mapping): the API distribution within the industrial drug reservoirs was found to be homogeneous while API aggregates were detected in laboratory scale samples manufactured with a non optimal mixing process. Second, the crosslinking process of the reservoirs was monitored at different temperatures with NIR spectroscopy. Conformity tests and Principal Component Analysis (PCA) were performed on the collected data to find out the relation between the temperature and the time necessary to reach the crosslinking endpoints. An agreement was found between the conformity test results and the PCA results. Compared to the conformity test method, PCA had the advantage to discriminate the heating effect from the crosslinking effect occurring together during the monitored process. Therefore the 2 approaches were found to be complementary. Third, based on the HPLC reference method, a NIR model able to quantify the API in the drug reservoir was developed and thoroughly validated. Partial Least Squares (PLS) regression on the calibration set was performed to build prediction models of which the ability to quantify accurately was tested with the external validation set. The 1.2% Root Mean Squared Error of Prediction (RMSEP) of the NIR model indicated the global accuracy of the model. The accuracy profile based on tolerance intervals was used to generate a complete validation report. The 95% tolerance interval calculated on the validation results indicated that each future result will have a relative error below ±5% with a probability of at least 95%. In conclusion, 3 critical quality attributes of silicone-based drug reservoirs were quickly and efficiently evaluated by NIR and Raman spectroscopy.