Changes in the solid state of anhydrous and hydrated forms of sodium naproxen under different grinding and environmental conditions: Evidence of the formation of new hydrated forms

Application of TGA/c-DTA for Distinguishing between Two Forms of Naproxen in Pharmaceutical Preparations

Naproxen is one of the most used non-steroidal anti-inflammatory drugs (NSAIDs). It is used to treat pain of various origins, inflammation and fever. Pharmaceutical preparations containing naproxen are available with prescription and over-the-counter (OTC). Naproxen in pharmaceutical preparations is used in the form of acid and sodium salt. From the point of view of pharmaceutical analysis, it is crucial to distinguish between these two forms of drugs. There are many costly and laborious methods to do this. Therefore, new, faster, cheaper and, at the same time, simple-to-perform identification methods are sought. In the conducted studies, thermal methods such as thermogravimetry (TGA) supported by calculated differential thermal analysis (c-DTA) were proposed to identify the type of naproxen in commercially available pharmaceutical preparations. In addition, the thermal methods used were compared with pharmacopoeial methods for the identification of compounds, such as high-performance liquid chromatography (HPLC), Fourier-transform infrared spectroscopy (FTIR), UV-Vis spectrophotometry, and a simple colorimetric analyses. In addition, using nabumetone, a close structural analog of naproxen, the specificity of the TGA and c-DTA methods was assessed. Studies have shown that the thermal analyses used are effective and selective in distinguishing the form of naproxen in pharmaceutical preparations. This indicates the potential possibility of using TGA supported by c-DTA as an alternative method.

Spectroscopic evaluation on pseudopolymorphs of sodium naproxen

This paper demonstrates the assessment of vibrational spectroscopy methods such as middle infrared, near infrared and Raman spectroscopy (FTIR, FT-NIR, Raman) for the identification of pseudopolymorphic forms of a model active pharmaceutical ingredient (API) - sodium naproxen (NpxNa). NpxNa, in the form of three different pseudopolymorphs, was investigated by methods dedicated for solid state characterization: DSC (differential scanning calorimetry), XPRD (powder X-ray diffraction), SEM (scanning electron microscopy) and Karl Fischer titration. Novelty in the results sourced in the usage of the method not applied so far to identify pseudopolymorphic forms of NpxNa, that is, FTIR and FT-NIR. Based on the obtained reproduceable results, various pseudopolymorphic forms were successfully evaluated. Spectroscopic data were correlated with DSC and XPRD results. It was concluded that the combination of band's variations visible on the spectra of pseudopolymorphic forms will allow to interpretate the results unequivocally in case of crucial stability tests of medicinal substance or during on-line pharmaceutical process development by FTIR, FT-NIR and Raman spectroscopy.

Spray drying of naproxen and naproxen sodium for improved tableting and dissolution - physicochemical characterization and compression performance

In this work, the tabletability and dissolution of spray-dried forms of naproxen and its sodium salt were compared with those of unprocessed drugs. Solutions of naproxen or naproxen sodium alone or with HPMC (5% w/w of drug content) were spray dried. Scanning electron micrographs showed that naproxen sodium spray-dried particles were spherical, whereas those of naproxen were non-spherical but isodiametric. Powder x-ray diffraction and thermal analysis indicated that co-spray drying with HPMC resulted in reduced crystallinity of naproxen and higher naproxen sodium dihydrate content. FTIR and Raman analysis showed shifting, merging or elimination of bands in the spectra of the co-spray dried products signifying solid-state alterations. When mixed with suitable processing aids (7% w/w), all co-spray dried powders produced satisfactory tablets in the pressure range 73-295 MPa. Conversely, physical mixtures of naproxen compressed with the same aids failed tableting, whereas naproxen sodium produced weak tablets. Dissolution tests showed significant improvement for co-spray dried drugs tablets. Therefore, since the large therapeutic doses of naproxen and sodium naproxen limit the use of tableting aids, the improved compaction and dissolution performance of the spray-dried forms may be a formulation alternative.

Polymorph Impact on the Bioavailability and Stability of Poorly Soluble Drugs

Drugs with low water solubility are predisposed to poor and variable oral bioavailability and, therefore, to variability in clinical response, that might be overcome through an appropriate formulation of the drug. Polymorphs (anhydrous and solvate/hydrate forms) may resolve these bioavailability problems, but they can be a challenge to ensure physicochemical stability for the entire shelf life of the drug product. Since clinical failures of polymorph drugs have not been uncommon, and some of them have been entirely unexpected, the Food and Drug Administration (FDA) and the International Conference on Harmonization (ICH) has required preliminary and exhaustive screening studies to identify and characterize all the polymorph crystal forms for each drug. In the past, the polymorphism of many drugs was detected fortuitously or through manual time consuming methods; today, drug crystal engineering, in particular, combinatorial chemistry and high-throughput screening, makes it possible to easily and exhaustively identify stable polymorphic and/or hydrate/dehydrate forms of poorly soluble drugs, in order to overcome bioavailability related problems or clinical failures. This review describes the concepts involved, provides examples of drugs characterized by poor solubility for which polymorphism has proven important, outlines the state-of-the-art technologies and discusses the pertinent regulations.