Stability Assessment of a Novel 3D-Printed Oral Dosage Form of Mexiletine Hydrochloride: A Six-Month Shelf-Life Study

This study presents the first evaluation of the shelf life of a novel three-dimensional (3D) printed formulation of Mexiletine Hydrochloride (HCl) over a six-month storage period. Mexiletine HCl was incorporated into a patient-personalized solid oral dosage form using a Semi-Solid Extrusion (SSE) 3D printing technique, and was then subjected to a preliminary stability assessment. We evaluated physical and chemical stability under ICH-recommended storage conditions, taking an important first step toward future full ICH-compliant studies. 3D-printed tablets were stored in a climatic cabinet, at 25 ± 2 °C and relative humidity 60 ± 5% (RH). The tablets were then evaluated for drug content analysis and impurities at 0 and 6 months of storage. Throughout the evaluation period, the printed tablets retained their physical characteristics, including shape and color, and exhibited no significant deviation in drug content and weight. Moreover, no detectable levels of degradation products or impurities were observed, as confirmed by validated analytical methods. These findings collectively indicate that the 3D-printed Mexiletine HCl formulation demonstrates excellent stability under room temperature storage conditions—information that is essential for advancing the formulation along regulatory and commercial pathways. Our data address the common trade-off between printability and stability, demonstrating that a formulation optimized for SSE printing can maintain stability under standard storage conditions.