Robust Crystallization Process Development for the Metastable δ-form of Pyrazinamide

The pressure–temperature phase diagram of tetramorphic pyrazinamide

All four pyrazinamide polymorphs possess a stable domain under ordinary pressure; α is the stable form at room temperature.

Tackling quantitative polymorphic analysis through fixed-dose combination tablets production. Pyrazinamide polymorphic assessment

Pyrazinamide (PZA), Rifampicin (RIF), Isoniazid (ISH) and Ethambutol (ETB) form the core for the treatment of Tuberculosis, today a devastating disease in low-income populations around the world. These drugs are usually administrated by fixed-dose combination (FDC) products, to favour the patient compliance and prevent bacterial resistance. PZA exists in four enantiotropically-related polymorphs (Forms α, δ, β and γ), but only Form α is considered suitable for pharmaceutical products due to its stability and bioavailability properties. The classical approaches to address solid-state (microscopy, X-ray diffraction and calorimetry) shows limitations for quantification of polymorphs in the presence of excipients and other active components, as in the case of FDC tablets. In this work, an overall strategy was developed using near infrared spectroscopy (NIR) coupled to partial least squares regression (PLS) to quantify Form α of PZA in drug substance (raw material) and PZA/RIF/ISH-FDC tablets. For this purpose, two PLS models were constructed, one for drug substance preparing training (n = 30) and validation (n = 18) samples with a ternary composition (Form α/Form δ/Form γ), and other for FDC drug products, also including the appropriate amount of RIF, ISH and the matrix of excipients in order to simulate the environment of PZA/RIF/ISH association. The NIR-PLS models were optimized using a novel smart approach based on radial optimization (full range, 3 L V and MSC-D' and SNV-D' as pre-treatment, for raw material and FDC tablets, respectively). During the validation step, both methods showed no bias or systematic errors and yielded satisfactory recoveries (102.5 ± 3.1 % for drug substance and 98.7 ± 1.5 % for FDC tablets). When commercial drug substance was tested, NIR-PLS was able to predict the content of Form α (0.98 ± 0.01 w/w). The model for FDC tablets allowed estimating polymorphic purity in intact (0.984 ± 0.003 w/w), sectioned (0.986 ± 0.002 w/w), and powered (0.985 ± 0.004 w/w) tablets, showing the methodology could be applied to a different stage of the process (i.e premixed-powders or granulates). The suitability of the method was also verified when Form α was satisfactorily analysed in FDC fortified with Form δ and Form γ to reach 0.78, 0.88 and 0.98 w/w, Form α. This strategy results in an excellent alternative to ensure the polymorphic purity of PZA throughout the overall pharmaceutical manufacturing process.

Polymorphs and Amorphous State of Glipizide: Preparation and Solid-State Transformations

The solid-state diversity of active pharmaceutical ingredients can provide theoretical guidance for the production and storage of drugs. In this study, three solid forms of glipizide were obtained through various methods, and the solid-state transformations were extensively investigated. Form I could be prepared using evaporative crystallization, cooling crystallization, anti-solvent crystallization, and solvent-mediated slurry conversion experiments (SSCE). Form II was produced by milling. Form III was obtained by milling and SSCE. The results of solid-state transformations indicated that Form I transformed to II during neat milling at 25 °C. In contrast, solvent inhibited the solid-state transformations of Form I under liquid-assisted milling. Forms II and III remained invariable under neat milling at 25 °C, and solid-state transformation of Form III also did not occur in the liquid-assisted milling. In SSCE, the solvent's nature and its temperature significantly influenced the solid-state conversion of amorphous glipizide. Form II converted to either Form I or III in water above 50 °C, and only transformed into Form I at 25 °C. However, the solid-state transformation did not occur when pure Form I or III was stirred in water. Form II also converted to Form I in the organic solvents SSCE at different temperatures.