Tailoring the use of excipients in bottom-up production of naproxen crystal suspensions via membrane technology.

Long-acting crystal suspensions of active pharmaceutical ingredients (API) mostly comprised of an API, a suspension media (water) and excipients and provide sustained API release over time. Excipients are crucial for controlling particle size and to achieve the stability of the API crystals in suspension. A bottom-up process was designed to produce long-acting crystal suspensions whilst investigating the excipient requirements during the production process and the subsequent storage. PVP K30 emerged as the most effective excipient for generating stable naproxen crystals with the desired size of 1 to 15 µm, using ethanol as solvent and water as anti-solvent. Calculations, performed based on the crystal properties and assuming complete PVP K30 adsorption on the crystal surface, revealed lower PVP K30 requirements during storage compared to initial crystal generation. Consequently, a membrane-based diafiltration process was used to determine and fine-tune PVP K30 concentration in the suspension post-crystallization. A seven-stage diafiltration process removed 98 % of the PVP K30 present in the suspension thereby reducing the PVP-to-naproxen ratio from 1:2 to 1:39 without impacting the stability of naproxen crystals in suspension. This work provides insights into the excipient requirements at various production stages and introduce the membrane-based diafiltration for precise excipient control after crystallization.

Mutual Impact of Phase Separation/Crystallization and Water Sorption in Amorphous Solid Dispersions.

The molecular integration of poorly water soluble active pharmaceutical ingredients (APIs) in a suitable polymeric matrix is a possible approach to enhance the dissolution behavior and solubility of these APIs. Like all newly developed pharmaceutical formulations, these formulations (often denoted as amorphous solid dispersions (ASDs)) need to undergo storage stability tests at defined relative humidity (RH) and temperature conditions. In a previous work ( Int. J. Pharm. 2017 ; 532 , 635 - 646 ), it was shown that thermodynamic modeling can be successfully used to predict the long-term stability of ASDs against API crystallization and moisture-induced amorphous-amorphous phase separation (MIAPS). This work in turn demonstrates the prediction of water sorption in ASDs accounting for the potential occurrence of API crystallization and MIAPS. The water sorption and phase behavior of ASDs containing the APIs felodipine and ibuprofen incorporated in three different hydrophilic polymers poly(vinylpyrrolidone), poly(vinyl acetate), and poly(vinylpyrrolidone-co-vinyl acetate) at the conditions 25 °C/60% RH and 40 °C/75% RH were predicted using the perturbed-chain statistical-associating fluid theory (PC-SAFT). The predictions were successfully validated via two-year-lasting water sorption experiments. It was shown that crystallization of the API and MIAPS on the one hand and water sorption in the ASDs on the other hand dramatically influence each other and that this behavior can even be quantitatively predicted by PC-SAFT, which already provides valuable insights at early stages of formulation development.