Effect of Span 20 Feeding Zone in the Twin Screw Extruder on the Properties of Amorphous Solid Dispersion of Ritonavir

Role of rheology in formulation and process design of hot melt extruded amorphous solid dispersions

Hot melt extrusion (HME) has been widely used as a continuous and highly flexible pharmaceutical manufacturing process for the production of a variety of dosage forms. In particular, HME enables preparation of amorphous solid dispersions (ASDs) which can improve bioavailability of poorly water-soluble drugs. The rheological properties of drug-polymer mixtures can significantly influence the processability of drug formulations via HME and eventually the end-use product properties such as physical stability and drug release. The objective of this review is to provide an overview of various rheological techniques and properties that can be used to evaluate the flow behavior and processability of the drug-polymer mixtures as well as formulation characteristics such as drug-polymer interactions, miscibility/solubility, and plasticization to improve the HME processability. An overview of the thermodynamics and kinetics of ASD processing by HME is also provided, as well as aspects of scale-up and process modeling, highlighting rheological properties on formulation design and process development. Overall, this review provides valuable insights into critical rheological properties which can be used as a predictive tool to optimize the HME processing conditions.

The Development of an Oral Solution Containing Nirmatrelvir and Ritonavir and Assessment of Its Pharmacokinetics and Stability

Paxlovid®, a co-packaged medication comprised of separate tablets containing two active ingredients, nirmatrelvir (NRV) and ritonavir (RTV), exhibits good effectiveness against coronavirus disease 2019 (COVID-19). However, the size of the NRV/RTV tablets makes them difficult for some patients to swallow, especially the elderly and those with dysphagia. Therefore, an oral liquid formulation that can overcome this shortcoming and improve patient compliance is required. In this study, we developed a liquid formulation containing NRV and RTV by adopting strategies that used co-solvents and surfactants to enhance the solubility and inhibit possible recrystallization. The in vitro release results showed that NRV and RTV could be maintained at high concentrations in solution for a certain period in the investigated media. In vivo studies in rats showed that the oral bioavailability of NRV/RTV solution was significantly enhanced. Compared to Paxlovid® tablets, the AUC(0-t) of NRV and RTV increased by 6.1 and 3.8 times, respectively, while the Cmax increased by 5.5 times for both. Furthermore, the promoting effect of the absorption of RTV on the bioavailability of NRV was confirmed. Experiments with a beagle showed a similar trend. Stability studies were also conducted at 4 °C, 25 °C, and 40 °C for 90 days, indicating that the oral liquid formulation was physically and chemically stable. This study can be used as a valuable resource for developing and applying oral liquid NRV/RTV formulations in a clinical context.