An Insight into the Impact of Thermal Process on Dissolution Profile and Physical Characteristics of Theophylline Tablets Made through 3D Printing Compared to Conventional Methods

Revealing Three-Dimensional Printing Technology Advances for Oral Drug Delivery: Application to Central-Nervous-System-Related Diseases

Background/Objectives. Central nervous system (CNS)-related diseases such as Alzheimer's and Parkinson's, Attention Deficit Hyperactive Disorder (ADHD), stroke, epilepsy, and migraines are leading causes of morbidity and disability worldwide. New solutions for drug delivery are increasingly needed. In this context, three-dimensional (3D) printing technology has introduced innovative alternatives to produce more efficient medicines with diverse features, patterns, and consistencies, particularly oral medications. Even though research in this area is growing rapidly, no study has thoroughly analyzed 3D printing oral drug delivery progress for the CNS. To fill this gap this study pursues to determine a technological landscape in this field. Methods. For this aim, a Competitive Technology Intelligence (CTI) methodology was applied, examining 747 publications from 1 January 2019 to 20 May 2024 published in the Scopus database. Results. The main advances identified comprise six categories: 3D printing techniques, characteristics and applications, materials, design factors, user acceptance, and quality processes. FDM was identified as the main technique for pharmaceutical use. The main applications include pills, polypills, caplets, gel caps, multitablets, orodispersible films, and tablets, featuring external patterns and internal structures with one or more active substances. Insights show that the most utilized materials are thermoplastic polymers like PLA, PVA, PCL, ABS, and HIPS. A novel design factor involves release patterns using compartments of varying thicknesses and volumes in the core. Additionally, advances in specialized software have enabled the creation of highly complex designs. In the user acceptance category, oral drugs dosages are tailored to the specific needs and preferences of neurological patients. Finally, for the quality aspect, the precision in Active Pharmaceutical Ingredient (API) dosage and controlled-release mechanisms are critical, given the narrow margin between therapeutic doses and toxicity for CNS diseases. Conclusions. Revealing these advancements in 3D printing for oral drug delivery allows researchers, academics, and decision-makers to identify opportunities and allocate resources efficiently, promising enhanced oral medicaments for the health and well-being of individuals suffering from CNS disorders.

An investigation of the drug release kinetics of 3D-Printed two compartment Theophylline and Prednisolone tablets

Pharmaceutical 3D printing (3DP) not only offers the possibility of dose personalization but also the co-administration of multiple active pharmaceutical ingredients (APIs) in one combination tablet. In this study, Theophylline (TPH) and Prednisolone (PSL) were printed as bi-tablets, which are single tablets with two distinct separate compartments. New findings show that the combination therapy of TPH with systemic corticosteroids shows a highly synergistic effect in the treatment of pulmonary diseases. For TPH, a drug with a narrow therapeutic window (NTW), precise sustained release requirements are mandatory, while PSL requires immediate drug release and is individually administered in doses specifically tied to the treatment progression. The study aims to understand the extent to which the combination of two tablet compartments influences the individual drug dissolution kinetics of the respective single compartments. Utilizing a full factorial statistical experimental design, various practically relevant doses were produced, investigated for their drug release, analyzed using different mathematical model fits, and compared with respective mono-tablets. The results show that the sustained drug release of TPH is not significantly influenced by the addition of a second compartment in relationship to respective doses. Individualization of bi-tablet doses while maintaining similar release profiles is possible with the given design setup, as release curves still show high similarity. In all tablet designs, PSL release occurred sufficiently fast, with the release rate correlating to the surface area-to-volume ratio (SA/V) as the main determining parameter.

Impact of Simulated Gastrointestinal Fluid: Viscosity, Surface Tension, and pH on the Dissolution and Rheology Assessment of Viscosity of Two Commercial Candesartan Cilexetil Products

Objectives

The aim of this study was to ivnestigate the effect of simulated gastrointestinal viscosity, surface tension, and pH on the dissolution rate of two commercial candesartan cilexetil (CC) products.

Materials and Methods

In vitro dissolution of two commercial CC products and immediate release of 16 mg of CC were applied under two conditions: (1) the requirements of the United States Pharmacopeia (USP) and (2) conditions physiologically related to the gastrointestinal tract mimicking viscous food intake. The solubility of CC in different simulation fluids was also measured. The dissolution media's viscosity, surface tension, and pH were also measured. The viscosity of the gel layer was measured during CC dissolution.

Results

The CC dissolution rate was highest in the USP medium. It was found that the media type affected CC dissolution. The non-USP media exhibited a slower dissolution rate than the USP specification. The highest viscosity media lowered the dissolution rate in one of the CC products. Acidic pH showed a significant decrease in dissolution for both CC products. The solubility of CC was affected by solvent type (p value < 0.001).

Conclusion

Higher viscosity media slow the dissolution rate of a product, where a gel layer forms on the tablet surface.The results show variation in the dissolution media. This may reveal differences in the dissolution rates of the same drug in different products and media. Considering, viscosity's effect on dissolution might improve patient outcomes when treated with different products.

Application of 3D printing on the design and development of pharmaceutical oral dosage forms

3D printing technologies confer an unparalleled degree of control over the material distribution on the structures they produce, which has led them to become an extremely attractive research topic in pharmaceutical dosage form development, especially for the design of personalized treatments. With fine tuning in material selection and careful design, these technologies allow to tailor not only the amount of drug administered but the biopharmaceutical behaviour of the dosage forms as well. While fused deposition modelling (FDM) is still the most studied 3D printing technology in this area, others are gaining more relevance, which has led to many new and exciting dosage forms developed during 2022 and 2023. Considering that these technologies, in time, will join the current manufacturing methods and with the ever-increasing knowledge on this topic, our review aims to explore the advantages and limitations of 3D printing technologies employed in the design and development of pharmaceutical oral dosage forms, giving special focus to the most important aspects governing the resulting drug release profiles.

Effect of pH, Ionic Strength and Agitation Rate on Dissolution Behaviour of 3D-Printed Tablets, Tablets Prepared from Ground Hot-Melt Extruded Filaments and Physical Mixtures

With the current focus on 3D-printing technologies, it is essential to understand the processes involved in such printing methods and approaches to minimize the variability in dissolution behaviour to achieve better quality control outcomes. For this purpose, two formulations of theophylline tablets were prepared using hydroxypropyl cellulose (HPC) and ethyl cellulose (EC). Among the two types of tablets, three different methods (physical mixture (PM), hot-melt extrusion (HME) and 3D-printing fused deposition modelling (FDM)) were applied and their dissolution behaviours were studied under various conditions using a biodissolution tester. This was carried out at pH values of 1.2, 2.2, 5.8, 6.8, 7.2 and 7.5, mimicking the medium in the gastrointestinal tract. Dissolution tests under two dipping rates (10 dpm and 20 dpm) and two ionic strengths (0.2 M and 0.4 M) were conducted to mimic fed and fasting conditions. The dissolution efficiency (DE%), release rate, similarity factor (f₂) and difference factor (f₁) were calculated. When comparing the DE%, the formulation containing EC showed less sensitivity to changes in the dipping rate and ionic strength compared to the HPC formulation. As for the manufacturing method, 3D-printing FDM could improve the robustness of the dissolution behaviour of both formulations to dipping rate changes. However, for ionic strength changes, the effect of the manufacturing method was dependent on the formulation composition. For example, the 3D-printed tablets of the HPC formulation were more sensitive to changes in ionic strength compared to the EC-containing formulation. The release mechanism also changed after the thermal process, where n values in the Korsmeyer-Peppas model were much higher in the printing and HME methods compared to the PM. Based on the formulation composition, the 3D-printing method could be a good candidate method for tablets with a robust dissolution behaviour in the GI tract. Compared to HPC polymers, using hydrophobic EC polymers in printable formulations can result in a more robust dissolution behaviour in fed and fasting states.

A Refined Hot Melt Printing Technique with Real-Time CT Imaging Capability

Personalised drug delivery systems with the ability to offer real-time imaging and control release are an advancement in diagnostic and therapeutic applications. This allows for a tailored drug dosage specific to the patient with a release profile that offers the optimum therapeutic effect. Coupling this application with medical imaging capabilities, real-time contrast can be viewed to display the interaction with the host. Current approaches towards such novelty produce a drug burst release profile and contrasting agents associated with side effects as a result of poor encapsulation of these components. In this study, a 3D-printed drug delivery matrix with real-time imaging is engineered. Polycaprolactone (PCL) forms the bulk structure and encapsulates tetracycline hydrochloride (TH), an antibiotic drug and Iron Oxide Nanoparticles (IONP, Fe₃O₄), a superparamagnetic contrasting agent. Hot melt extrusion (HME) coupled with fused deposition modelling (FDM) is utilised to promote the encapsulation of TH and IONP. The effect of additives on the formation of micropores (10-20 µm) on the 3D-printed surface was investigated. The high-resolution process demonstrated successful encapsulation of both bioactive and nano components to present promising applications in drug delivery systems, medical imaging and targeted therapy.

Evaluation of Hydroxyethyl Cellulose Grades as the Main Matrix Former to Produce 3D-Printed Controlled-Release Dosage Forms

Diclofenac sodium tablets were successfully prepared via hot-melt extrusion (HME) and fused deposition modeling (FDM), using different molecular-weight (Mw) grades of hydroxyethyl cellulose (HEC) as the main excipient. Hydroxypropyl cellulose (HPC) was added to facilitate HME and to produce drug-loaded, uniform filaments. The effect of the HEC grades (90–1000 kDa) on the processability of HME and FDM was assessed. Mechanical properties of the filaments were evaluated using the three-point bend (3PB) test. Breaking stress and distance were set in relation to the filament feedability to identify printer-specific thresholds that enable proper feeding. The study demonstrated that despite the HEC grade used, all formulations were at least printable. However, only the HEC L formulation was feedable, showing the highest breaking stress (29.40 ± 1.52 MPa) and distance (1.54 ± 0.08 mm). Tablet drug release showed that the release was Mw dependent up to a certain HEC Mw limit (720 kDa). Overall, the release was driven by anomalous transport due to drug diffusion and polymer erosion. The results indicate that despite being underused in FDM, HEC is a suitable main excipient for 3D-printed dosage forms. More research on underutilized polymers in FDM should be encouraged to increase the limited availability.