Exploring tablet design options for tailoring drug release and dose via fused deposition modeling (FDM) 3D printing

Regulations on excipients used in 3D printing of pediatric oral forms

A promising solution to customize oral drug formulations for the pediatric population has been found in the use of 3D printing, in particular Fused Deposition Modeling (FDM) and Semi-Solid Extrusion (SSE). Although formulation development is currently limited to research studies, the rapid advances in 3D printing warn of the need for regulation. Indeed, even if the developed formulations include pharmaceutical excipients used to produce traditional oral forms such as tablets, the quantities of excipients used must be adapted to the process. Therefore, the aim of this literature review is to provide a synthesis of the available safety data on excipients mainly used in extrusion-based 3D printing for the pediatric population. A total of 39 relevant articles were identified through two scientific databases (PubMed and Science Direct). Then, groups of the main excipients were listed including their general information (name, chemical structure and pharmaceutical use) and a synthesis of the available safety data extracted from several databases. Finally, the role of the excipients in 3D printing, the amount used in formulations and the oral dose administered per form are presented.

Rising role of 3D-printing in delivery of therapeutics for infectious disease

Modern drug delivery to tackle infectious disease has drawn close to personalizing medicine for specific patient populations. Challenges include antibiotic-resistant infections, healthcare associated infections, and customizing treatments for local patient populations. Recently, 3D-printing has become a facilitator for the development of personalized pharmaceutic drug delivery systems. With a variety of manufacturing techniques, 3D-printing offers advantages in drug delivery development for controlled, fine-tuned release and platforms for different routes of administration. This review summarizes 3D-printing techniques in pharmaceutics and drug delivery focusing on treating infectious diseases, and discusses the influence of 3D-printing design considerations on drug delivery platforms targeting these diseases. Additionally, applications of 3D-printing in infectious diseases are summarized, with the goal to provide insight into how future delivery innovations may benefit from 3D-printing to address the global challenges in infectious disease.

3D-printed prednisolone phosphate suppositories with tunable dose and rapid release for the treatment of inflammatory bowel disease

Established medicines are often not tailored to the needs of the pediatric population, causing difficulties with administration or dosing. Three-dimensional (3D) printing technology allows novel approaches for compounding of personalized medicine, as is exemplified in this study for the automated compounding of rectal preparations for children. We investigated the material requirements to print prednisolone phosphate-loaded suppositories with tunable dose and rapid drug release for the treatment of inflammatory bowel diseases. Three formulations containing 4 % w/w prednisolone sodium phosphate (PSP) and different amounts of hydroxypropyl cellulose (HPC) and mannitol as excipients were printed as suppositories with a fused deposition modeling (FDM) 3D-printer. Dissolution studies showed that the PSP release rate was increased when higher weight fractions of mannitol were added as a pore former, with 90 % drug release within 30 min for mannitol 48 % w/w. We further printed suppositories with 48 % mannitol with different infill densities and dimensions to tune the dose. Our findings demonstrated that 3D-printed suppositories with PSP doses ranging from 6 to 30 mg could be compounded without notably affecting the dissolution kinetics, ensuring equivalent therapeutic efficacies for different doses.

Investigations of hybrid infill pattern in additive manufactured tablets: A novel approach towards tunable drug release

The significance of 3D printing has risen exponentially in biomedical and pharmaceutical applications. Its potential in the field of fabricating drug delivery systems, by virtue of processing biocompatible polymers, has been very lucrative. This work aims to tap the interstitial drug delivery kinetics that are often inaccessible through machine-specific infill patterns in additive manufactured tablets fabricated using PVA biopolymer as an excipient. In this regard, a myo-inositol containing tablet has been printed using Fused Deposition Modeling preceded by Hot Melt Extrusion drug loading route. Two machine-specific infill patterns were taken, namely straight and grid. Later, these two distinct patterns were juxtaposed to obtain novel hybrid infill patterns in the tablets. Then, these tablets and their filament were subjected to various thermal, mechanical, imaging and pharmaceutical characterization tests to assess the feasibility of the research attempt. Finally, dissolution tests were conducted to evaluate their dissolution behavior over a time period. The characterization tests proved the scientific viability of this attempt along with amorphous existence of drug in the polymeric filament. The dissolution results showed favorable drug release by achieving interstitial dissolution timings with surface area/volume (SA/V) ratio being found to be the principal factor.

Development of Subdermal Implants Using Direct Powder Extrusion 3D Printing and Hot-Melt Extrusion Technologies

Implants are drug delivery platforms that consist of a drug-polymer matrix with the ability of providing a localized and efficient controlled release of the drug with minimal side effects and achievement of the desired therapeutic outcomes with low drug loadings. Direct powder extrusion (DPE) 3D printing technology involves the extrusion of material through a nozzle of the printer in the form of pellets or powder. The present study aimed at investigating the use of the CELLINK BIO X™ bioprinter using DPE 3D printing technique to fabricate and evaluate the impact of different shapes (cuboid, cylinder, and tube) of raloxifene hydrochloride (RFH)-loaded subdermal implants on the release of RFH from the implants. This study further evaluated the impact of different processing techniques, viz., hot-melt extrusion (HME) technology vs. DPE 3D printing technique, on the release of RFH from the implants fabricated by each processing technique. All the fabricated implants were characterized by XRD, DSC, SEM, and FTIR, and evaluated for their water uptake, mass loss, and in vitro RFH release. The current study successfully demonstrated a great opportunity of controlling and/or tuning the release of RFH from the subdermal implants by altering the implant shape, and hence surface area, and could be a great contribution and/or addition to the personalization of medicines and improvement of patient compliance.

Development of 3D-Printed Bicompartmental Devices by Dual-Nozzle Fused Deposition Modeling (FDM) for Colon-Specific Drug Delivery

Dual-nozzle fused deposition modeling (FDM) is a 3D printing technique that allows for the simultaneous printing of two polymeric filaments and the design of complex geometries. Hence, hybrid formulations and structurally different sections can be combined into the same dosage form to achieve customized drug release kinetics. The objective of this study was to develop a novel bicompartmental device by dual-nozzle FDM for colon-specific drug delivery. Hydroxypropylmethylcellulose acetate succinate (HPMCAS) and polyvinyl alcohol (PVA) were selected as matrix-forming polymers of the outer pH-dependent and the inner water-soluble compartments, respectively. 5-Aminosalicylic acid (5-ASA) was selected as the model drug. Drug-free HPMCAS and drug-loaded PVA filaments suitable for FDM were extruded, and their properties were assessed by thermal, X-ray diffraction, microscopy, and texture analysis techniques. 5-ASA (20% w/w) remained mostly crystalline in the PVA matrix. Filaments were successfully printed into bicompartmental devices combining an outer cylindrical compartment and an inner spiral-shaped compartment that communicates with the external media through an opening. Scanning electron microscopy and X-ray tomography analysis were performed to guarantee the quality of the 3D-printed devices. In vitro drug release tests demonstrated a pH-responsive biphasic release pattern: a slow and sustained release period (pH values of 1.2 and 6.8) controlled by drug diffusion followed by a faster drug release phase (pH 7.4) governed by polymer relaxation/erosion. Overall, this research demonstrates the feasibility of the dual-nozzle FDM technique to obtain an innovative 3D-printed bicompartmental device for targeting 5-ASA to the colon.

The Influence of Shape Parameters on Unidirectional Drug Release from 3D Printed Implants and Prediction of Release from Implants with Individualized Shapes

The local treatment of diseases by drug-eluting implants is a promising tool to enable successful therapy under potentially reduced systemic side effects. Especially, the highly flexible manufacturing technique of 3D printing provides the opportunity for the individualization of implant shapes adapted to the patient-specific anatomy. It can be assumed that variations in shape can strongly affect the released amounts of drug per time. This influence was investigated by performing drug release studies with model implants of different dimensions. For this purpose, bilayered model implants in a simplified geometrical shape in form of bilayered hollow cylinders were developed. The drug-loaded abluminal part consisted of a suitable polymer ratio of Eudragit® RS and RL, while the drug-free luminal part composed of polylactic acid served as a diffusion barrier. Implants with different heights and wall thicknesses were produced using an optimized 3D printing process, and drug release was determined in vitro. The area-to-volume ratio was identified as an important parameter influencing the fractional drug release from the implants. Based on the obtained results drug release from 3D printed implants with individual shapes exemplarily adapted to the frontal neo-ostial anatomy of three different patients was predicted and also tested in an independent set of experiments. The similarity of predicted and tested release profiles indicates the predictability of drug release from individualized implants for this particular drug-eluting system and could possibly facilitate the estimation of the performance of customized implants independent of individual in vitro testing of each implant geometry.

Recent Advances in the Applications of Additive Manufacturing (3D Printing) in Drug Delivery: A Comprehensive Review

There has been a tremendous increase in the investigations of three-dimensional (3D) printing for biomedical and pharmaceutical applications, and drug delivery in particular, ever since the US FDA approved the first 3D printed medicine, SPRITAM® (levetiracetam) in 2015. Three-dimensional printing, also known as additive manufacturing, involves various manufacturing techniques like fused-deposition modeling, 3D inkjet, stereolithography, direct powder extrusion, and selective laser sintering, among other 3D printing techniques, which are based on the digitally controlled layer-by-layer deposition of materials to form various geometries of printlets. In contrast to conventional manufacturing methods, 3D printing technologies provide the unique and important opportunity for the fabrication of personalized dosage forms, which is an important aspect in addressing diverse patient medical needs. There is however the need to speed up the use of 3D printing in the biopharmaceutical industry and clinical settings, and this can be made possible through the integration of modern technologies like artificial intelligence, machine learning, and Internet of Things, into additive manufacturing. This will lead to less human involvement and expertise, independent, streamlined, and intelligent production of personalized medicines. Four-dimensional (4D) printing is another important additive manufacturing technique similar to 3D printing, but adds a 4th dimension defined as time, to the printing. This paper aims to give a detailed review of the applications and principles of operation of various 3D printing technologies in drug delivery, and the materials used in 3D printing, and highlight the challenges and opportunities of additive manufacturing, while introducing the concept of 4D printing and its pharmaceutical applications.

Production of Bi-Compartmental Tablets by FDM 3D Printing for the Withdrawal of Diazepam

Diazepam (DZP) is a long-acting benzodiazepine to treat anxiety or acute alcohol withdrawal. Although this class of drugs should be taken for a short period of time, many patients take them for longer than recommended, which has been linked to an increased risk of dementia and dependence. The present work aimed at using the dual-nozzle system of fused deposition modeling (FDM) 3D printers to prepare tablets with gradual doses of DZP with constant mass and size. Placebo and DZP-loaded filaments were prepared by hot-melt extrusion and used to print the bi-compartmental tablets. Thermal processing allowed the conversion of crystalline DZP to its amorphous counterpart. Tablets with different DZP contents were effectively printed with a mass, thickness and diameter average of 111.6 mg, 3.1 mm, and 6.4 mm, respectively. Microscopic data showed good adhesion between the different layers in the printed tablets. The desired drug contents were successfully achieved and were within the acceptance criteria (European Pharmacopeia). The combination of a placebo and drug-loaded extrudates proved to be beneficial in the production of tablets by FDM for patients in need of drug withdrawal.

Controlled Release of Felodipine from 3D-Printed Tablets with Constant Surface Area: Influence of Surface Geometry

In this study, 3D-printed tablets with a constant surface area were designed and fabricated using polylactic acid (PLA) in the outer compartment and polyvinyl alcohol and felodipine (FDP) in the inner compartment. The influences of different surface geometries of the inner compartment, namely, round, hexagon, square, and triangle, on drug release from 3D-printed tablets were also studied. The morphology and porosity of the inner compartment were determined using scanning electron microscopy and synchrotron radiation X-ray tomographic microscopy, respectively. Additionally, drug content and drug release were also evaluated. The results revealed that the round-shaped geometry seemed to have the greatest total surface area of the inner compartment, followed by square-shaped, hexagon-shaped, and triangle-shaped geometries. FDP-loaded 3D-printed tablets with triangle and hexagon surface geometries had the slowest drug release (about 80% within 24 h). In the round-shaped and square-shaped 3D-printed tablets, complete drug release was observed within 12 h. Furthermore, the drug release from triangle-shaped 3D-printed tablets with double the volume of the inner compartment was faster than that of a smaller volume. This was due to the fact that a larger tablet volume increased the surface area contacting the medium, resulting in a faster drug release. The findings indicated that the surface geometry of 3D-printed tablets with a constant surface area affected drug release. This study suggests that 3D printing technology may be used to develop oral solid dosage forms suitable for customized therapeutic treatments.

3D-Printed Fast-Dissolving Oral Dosage Forms via Fused Deposition Modeling Based on Sugar Alcohol and Poly(Vinyl Alcohol)-Preparation, Drug Release Studies and In Vivo Oral Absorption

Three-dimensional printing technology holds marked promise for the pharmaceutical industry and is now under intense investigation. Most research is aimed at a greater efficiency in printing oral dosage forms using powder bed printing or fused deposition modeling (FDM). Oral dosage forms printed by FDM tend to be hard objects, which reduce the risk of cracking and chipping. However, one challenge in printing oral dosage forms via FDM is achieving rapid drug release, because the materials for FDM are basically thermoplastic polymers with slow drug release properties. In this study, we investigated printing a fast-dissolving oral dosage form by adding sugar alcohol to a poly(vinyl alcohol)-based formulation for FDM. Filaments which contain sugar alcohol were successfully prepared, and objects were printed with them as oral dosage forms by FDM. On drug release testing, a printed oral dosage form in a ring shape which contained 55% maltitol showed a more than 85% drug release in 15 min. In vivo oral absorption of this printed oral dosage form in dogs was comparable to that of a conventional fast-dissolving tablet. Of particular interest, the drug release profile and drug amount of the oral dosage forms can be easily controlled by a change in shape using 3D Computer Aided Design. These characteristics will encourage the prevalence of FDM by the pharmaceutical industry, and contribute to the promotion of personalized medicine.

Preparation and advanced characterization of highly drug-loaded, 3D printed orodispersible tablets containing fluconazole

Due to the possibility of designing various spatial structures, three-dimensional printing can be implemented in the production of customized medicines. Nevertheless, the use of these methods for the production of dosage forms requires further optimization, understanding, and development of printouts' quality verification mechanisms. Therefore, the goal of our work was the preparation and advanced characterization of 3D printed orodispersible tablets (ODTs) containing fluconazole, printed by the fused deposition modeling (FDM) method. We prepared and analyzed 7 printable filaments containing from 10% to 70% fluconazole, used as model API. Obtaining a FDM-printable filament with such a high API content makes our work unique. In addition, we confirmed the 12-month stability of the formulation, which, to our knowledge, is the first study of this type. Next, we printed 10 series of porous tablets containing 50 mg of API from both fresh and stored filaments containing 20 %, 40 %, or 70 % fluconazole. We confirmed the high quality and precision of the printouts using scanning electron microscopy. The detailed analysis of the tablets' disintegration process included the Pharmacopeial test, but also the surface dissolution imaging analysis (SDI) and the test simulating oral conditions performed in own-constructed apparatus. For each composition, we obtained tablets disintegrating in less than 3 min, i.e., meeting the criteria for ODTs required by the European Pharmacopeia. The filaments' storage at ambient conditions did not affect the quality of the tablets. All printed tablets released over 95% of the fluconazole within 30 min. Moreover, the printouts were stable for two weeks.

Novel 3D Printed Modular Tablets Containing Multiple Anti-Viral Drugs: a Case of High Precision Drop-on-Demand Drug Deposition

3D printed drug delivery systems have gained tremendous attention in pharmaceutical research due to their inherent benefits over conventional systems, such as provisions for customized design and personalized dosing. The present study demonstrates a novel approach of drop-on-demand (DoD) droplet deposition to dispense drug solutions precisely on binder jetting-based 3D printed multi-compartment tablets containing 3 model anti-viral drugs (hydroxychloroquine sulfate - HCS, ritonavir and favipiravir). The printing pressure affected the printing quality whereas the printing speed and infill density significantly impacted the volume dispersed on the tablets. Additionally, the DoD parameters such as nozzle valve open time and cycle time affected both dispersing volume and the uniformity of the tablets. The solid-state characterization, including DSC, XRD, and PLM, revealed that all drugs remained in their crystalline forms. Advanced surface analysis conducted by microCT imaging as well as Artificial Intelligence (AI)/Deep Learning (DL) model validation showed a homogenous drug distribution in the printed tablets even at ultra-low doses. For a four-hour in vitro drug release study, the drug loaded in the outer layer was released over 90%, and the drug incorporated in the middle layer was released over 70%. In contrast, drug encapsulated in the core was only released about 40%, indicating that outer and middle layers were suitable for immediate release while the core could be applied for delayed release. Overall, this study demonstrates a great potential for tailoring drug release rates from a customized modular dosage form and developing personalized drug delivery systems coupling different 3D printing techniques.

Dose Titration of Solid Dosage Forms via FDM 3D-Printed Mini-Tablets

The robustness of 3D-printed mini-tablets as a platform to administer milligram dosages, intended for age-specific therapy, without the need of tablet splitting while maintaining similar release profiles, was investigated. Griseofulvin, as a model poorly water-soluble drug, and hydroxypropyl cellulose along with Kollicoat Protect as polymers were used to prepare filaments at 1-20% drug concentrations via hot-melt extrusion (HME). Higher drug concentrations served for testing the feasibility of a reduced number of mini-tablets to be administered. A reliable dose titration in the range 0.19-3.91 mg at a high accuracy (R2 of 0.999) was achieved through composite unit (multi-unit) mini-tablets. All mini-tablets produced had excellent content uniformity and their label claim values were within the acceptable range, proving that HME processing followed by 3D printing promotes content uniformity even for mini-tablets containing low drug doses (0.19 mg). Remarkably, the proposed approach allowed achieving similar drug release profiles via composite unit mini-tablets as well as single mini-tablets at high drug concentrations. In contrast, split tablets demonstrated different release behaviors, attributed to their size and shape differences. Overall, the distinct advantages of mini-tablets to provide dose flexibility while maintaining similar release profiles was demonstrated.

Tunable Drug Release from Fused Deposition Modelling (FDM) 3D-Printed Tablets Fabricated Using a Novel Extrudable Polymer

Three-dimensional (3D) printing is proving to be a pivotal technology for developing personalized dosage forms with bench to bedside feasibility. Fused deposition modelling (FDM) 3D printing has emerged as the most used technique wherein molten drug-loaded polymer filaments are deposited layer-by-layer to fabricate a predefined shape and internal geometry. However, for precise FDM 3D printing, it is imperative for the filaments to have peculiar mechanical/physicochemical properties, which the majority of the FDA/GRAS approved polymers lack. In the current study, a novel water-soluble polymer, Poly(2-ethyl-tetra-oxazoline) [PETOx] has been investigated as an extrudable and printable polymer with two different types of drug molecule—dextromethorphan hydrobromide (DXM) and hydrochlorothiazide (HCTZ). Hot-stage microscopy experiments of drug:polymer (1:1 w/w) and filaments were carried out at 25−275 °C. HCTZ-loaded filament showed higher toughness of 17 ± 3.25 × 106 J/m3 compared with DXM and drug-free filament. Moisture sorption and flexural analysis was performed to understand the correlation of mechanical properties and storage humidity to printability. Varying the number of outer perimeters of each layer (shell number) was observed to affect the drug release pattern from the printlets. The DXM one-shell printlet showed >80%, whereas the DXM five-shell printlet showed >60% of the drug release within 60 min. PETOx could prove to be a high-performance and versatile 3D printable polymer.

Transdermal delivery via medical device technologies

INTRODUCTION

Despite their effectiveness and indispensability, many drugs are poorly solvated in aqueous solutions. Over recent decades, the need for targeted drug delivery has led to the development of pharmaceutical formulations with enhanced lipid solubility to improve their delivery properties. Therefore, a dependable approach for administering lipid-soluble drugs needs to be developed.

AREAS COVERED

The advent of 3D printing or additive manufacturing (AM) has revolutionized the development of medical devices, which can effectively enable the delivery of lipophilic drugs to the targeted tissues. This review focuses on the use of microneedles and iontophoresis for transdermal drug delivery. Microneedle arrays, inkjet printing, and fused deposition modeling have emerged as valuable approaches for delivering several classes of drugs. In addition, iontophoresis has been successfully employed for the effective delivery of macromolecular drugs.

EXPERT OPINION

Microneedle arrays, inkjet printing, and fused deposition are potentially useful for many drug delivery applications; however, the clinical and commercial adoption rates of these technologies are relatively low. Additional efforts is needed to enable the pharmaceutical community to fully realize the benefits of these technologies.

Modified Release Kinetics in Dual Filament 3D Printed Individualized Oral Dosage Forms

On demand production of totally customizable combinative preparations is a central goal of a patient-centric pharmaceutical supply chain. Additive manufacturing techniques like fused deposition modeling (FDM) could be key technologies towards such individualized dosage forms. As so far only a limited number of studies on 3D printed combinative preparations applying FDM have been reported, a core-shell dosage form was the focus of the present study. Dosage forms with an initial and a sustained release part with theophylline as model API were successfully produced applying a dual nozzle FDM 3D printer. Investigations identified microstructural defects at the interface between the two formulations by means of µCT analysis. Dissolution testing proved the achievement of the intended release profile. In combination with additionally characterized release profile of single material prints of different shapes, the combinative release profiles could be predicted by developing model equations and taking into account the geometric composition. As these model approaches can accordingly facilitate the prediction of API release from 3D printed combinative preparations with only data from single material release. This is a first step towards a truly individualized and reliable patient-centric pharmaceutical supply via 3D printing.

The Advent of a New Era in Digital Healthcare: A Role for 3D Printing Technologies in Drug Manufacturing?

The technological revolution has physically affected all manufacturing domains, at the gateway of the fourth industrial revolution. Three-dimensional (3D) printing has already shown its potential in this new reality, exhibiting remarkable applications in the production of drug delivery systems. As part of this concept, personalization of the dosage form by means of individualized drug dose or improved formulation functionalities has concentrated global research efforts. Beyond the manufacturing level, significant parameters must be considered to promote the real-time manufacturing of pharmaceutical products in distributed areas. The majority of current research activities is focused on formulating 3D-printed drug delivery systems while showcasing different scenarios of installing 3D printers in patients' houses, hospitals, and community pharmacies, as well as in pharmaceutical industries. Such research presents an array of parameters that must be considered to integrate 3D printing in a future healthcare system, with special focus on regulatory issues, drug shortages, quality assurance of the product, and acceptability of these scenarios by healthcare professionals and public parties. The objective of this review is to critically present the spectrum of possible scenarios of 3D printing implementation in future healthcare and to discuss the inevitable issues that must be addressed.

Rheological Investigation of Hydroxypropyl Cellulose–Based Filaments for Material Extrusion 3D Printing

The rheological properties of drug–polymer mixtures have a significant influence on their processability when using transformative techniques, such as hot-melt-extrusion and material-extrusion 3D printing; however, there has been limited data on printable systems. This study investigated the rheological properties of 17 formulations of successful printed tablets for both immediate and controlled release. Hydroxypropyl cellulose was used in various ratios to obtain printable filaments in combination with various drugs (indomethacin or theophylline), polymers and disintegrants. The complex viscosity, shear thinning behavior and viscoelastic properties were affected by the drug load, polymer composite, disintegrant type, temperature and shear rate applied. Larger windows of processing viscosity were revealed. The viscosity of the printable blends could be as low as the range 10–1000 Pa·s at 100 rad/s angular frequency. All formulations showed shear thinning behavior with a broad slope of complex viscosity from −0.28 to −0.74. The addition of 30–60% drug or disintegrant tended to have greater viscosity values. While microcrystalline cellulose was found to be an alternative additive to lower the storage and loss modulus among disintegrants. This rheological data could be useful for the preformulation and further development of material-extrusion 3D-printing medicines.

Dose-independent drug release from 3D printed oral medicines for patient-specific dosing to improve therapy safety

Fused deposition modelling (FDM) 3D printing provides the ability to address individual patients' therapeutic needs without having to change the formulation every time. This is particularly interesting for dosing and release modelling. In this study, a geometry model was developed that can represent variable dosages while keeping the surface area to volume (SA/V) ratio alike, so the drug release profiles remain similar. The model was tested on three different formulations. Two BCS I active pharmaceutical ingredients (API), pramipexole and levodopa, and one BCS II API, praziquantel, were used. Polyvinyl alcohol (PVA, water soluble) and a combination of vinylpyrrolidone-vinyl acetate copolymer (PVP-VA, water soluble) and ethylene-vinyl acetate (EVA, water insoluble) were used as the polymer matrix. The curves were compared using the similarity factor (f₂ value) and mean dissolution time (MDT). Using a hollow cylinder-based (HCb) geometry model, a dose-independent drug release could be realized. For the PVA formulations, an 8-fold dose change could be obtained and for the EVA-PVP-VA formulation a factor of 5.5 could be achieved, with f₂ > 50. Due to the layer structure of the printed objects, very fine dose variation of 0.13 mg per layer is possible within these models. This allows variable dosing in small steps with only one basis formulation.

Fused Deposition Modeling as a Possible Approach for the Preparation of Orodispersible Tablets

Additive manufacturing technologies are considered as a potential way to support individualized pharmacotherapy due to the possibility of the production of small batches of customized tablets characterized by complex structures. We designed five different shapes and analyzed the effect of the surface/mass ratio, the influence of excipients, and storage conditions on the disintegration time of tablets printed using the fused deposition modeling method. As model pharmaceutical active ingredients (APIs), we used paracetamol and domperidone, characterized by different thermal properties, classified into the various Biopharmaceutical Classification System groups. We found that the high surface/mass ratio of the designed tablet shapes together with the addition of mannitol and controlled humidity storage conditions turned out to be crucial for fast tablet’s disintegration. As a result, mean disintegration time was reduced from 5 min 46 s to 2 min 22 s, and from 11 min 43 s to 2 min 25 s for paracetamol- and domperidone-loaded tablets, respectively, fulfilling the European Pharmacopeia requirement for orodispersible tablets (ODTs). The tablet’s immediate release characteristics were confirmed during the dissolution study: over 80% of APIs were released from printlets within 15 min. Thus, this study proved the possibility of using fused deposition modeling for the preparation of ODTs.

QbD guided development of immediate release FDM-3D printed tablets with customizable API doses

The objective of this work was to develop a fused deposition modeling (FDM) 3D printed immediate release (IR) tablet with flexibility in adjusting the dose of the active pharmaceutical ingredient (API) by scaling the size of the dosage form and appropriate drug release profile steadiness to the variation of dimensions or thickness of the deposited layers throughout the printing process. Polyvinyl alcohol-based filaments with elevated API content (50% w/w) were prepared by hot melt extrusion (HME), through systematic screening of polymeric formulations with different drug loadings, and their printability was evaluated by means of mechanical characterization. For the tablet fabrication step by 3D printing (3DP), the Quality by Design (QbD) approach was implemented by employing risk management strategies and Design of Experiments (DoE). The effects of the tablet design, tablet size and the layer height settings on the drug release and the API content were investigated. Between the two proposed original tablet architectures, the honeycomb configuration was found to be a suitable candidate for the preparation of IR dosage forms with readily customizable API doses. Also, a predictive model was obtained, which assists the optimization of variables involved in the printing phase and thereby facilitates the tailoring process.

Tailoring amlodipine release from 3D printed tablets: Influence of infill patterns and wall thickness

The aim of this study was to investigate the impact of infill patterns on the drug release of 3D-printed tablets and the possibility of tailoring drug release through the use of excipients. Furthermore, the influence of wall thickness was evaluated. Amlodipine was used as a model drug, polyvinyl alcohol (PVA) as a polymer and excipients including sodium starch glycolate (SSG) and hydroxypropyl methyl cellulose (HPMC) HME 4 M were used. Four different formulations were prepared. Firstly, the substances were mixed and then extruded by hot melt extrusion to form filaments. The obtained filaments were used to print amlodipine tablets by fused deposition modeling (FDM) 3D-printing technique. Each formulation was printed in four different infill patterns: zigzag, cubic, tri-hexagon and concentric, while infill density remained constant (20%). The mechanical properties of the obtained filaments were also evaluated using three-point bend test. Amlodipine tablets were printed with varying wall thickness (1 mm, 2 mm and 3 mm) and varying infill patterns. With regard to the infill patterns, higher drug release was achieved with zigzag infill pattern. The simultaneous effect of excipients and infill patterns on amlodipine release has been described and modeled through self - organizing maps (SOMs), which visualize the effect of these variables. Self-organizing maps confirmed the fastest drug release when the zigzag pattern and SSG were used, but also showed that the presence of HPMC HME 4 M was not decisive for drug release rate. As for the wall thickness, higher drug release was achieved with decreasing wall thickness. The results indicated that proper selection of excipients and/or adjusting the infill pattern and wall thickness are ways of tailoring drug release in FDM 3D printing. This study draws the attention to the importance of adjusting the settings of the printer and the usage of excipients to produce release-tailored medications.

Quality of FDM 3D Printed Medicines for Pediatrics: Considerations for Formulation Development, Filament Extrusion, Printing Process and Printer Design

3d printing is capable of providing dose individualization for pediatric medicines and translating the precision medicine approach into practical application. In pediatrics, dose individualization and preparation of small dosage forms is a requirement for successful therapy, which is frequently not possible due to the lack of suitable dosage forms. For precision medicine, individual characteristics of patients are considered for the selection of the best possible API in the most suitable dose with the most effective release profile to improve therapeutic outcome. 3d printing is inherently suitable for manufacturing of individualized medicines with varying dosages, sizes, release profiles and drug combinations in small batch sizes, which cannot be manufactured with traditional technologies. However, understanding of critical quality attributes and process parameters still needs to be significantly improved for this new technology. To ensure health and safety of patients, cleaning and process validation needs to be established. Additionally, adequate analytical methods for the in-process control of intermediates, regarding their printability as well as control of the final 3d printed tablets considering any risk of this new technology will be required. The PolyPrint consortium is actively working on developing novel polymers for fused deposition modeling (FDM) 3d printing, filament formulation and manufacturing development as well as optimization of the printing process, and the design of a GMP-capable FDM 3d printer. In this manuscript, the consortium shares its views on quality aspects and measures for 3d printing from drug-loaded filaments, including formulation development, the printing process, and the printed dosage forms. Additionally, engineering approaches for quality assurance during the printing process and for the final dosage form will be presented together with considerations for a GMP-capable printer design.

Enhanced Supersaturation via Fusion-Assisted Amorphization during FDM 3D Printing of Crystalline Poorly Soluble Drug Loaded Filaments

Filaments loaded with griseofulvin (GF), a model poorly water-soluble drug, were prepared and used for 3D printing via fused deposition modeling (FDM). GF was selected due to its high melting temperature, enabling lower temperature hot-melt extrusion (HME) keeping GF largely crystalline in the filaments, which could help mitigate the disadvantages of high HME processing temperatures such as filament quality, important for printability and the adverse effects of GF recrystallization on tablet properties. Novel aspects include single-step fusion-assisted ASDs generation during FDM 3D printing and examining the impact of tablet surface areas (SA) through printing multi-mini and square-pattern perforated tablets to further enhance drug supersaturation during dissolution. Kollicoat protect and hydroxypropyl cellulose were selected due to their low miscibility with GF, necessary to produce crystalline filaments. The drug solid-state was assessed via XRPD, DSC and FT-IR. At 165 °C HME processing temperature, the filaments containing ~80% crystalline GF were printable. Fusion-assisted 3D printing led to GF supersaturation of ~153% for cylindrical tablets and ~293% with the square-pattern perforated tablets, indicating strong monotonous impact of tablet SA. Dissolution kinetics of drug release profiles indicated Fickian transport for tablets with higher SA, demonstrating greater SA-induced drug supersaturation for well-designed 3D printed tablets.

Polymers in pharmaceutical additive manufacturing: A balancing act between printability and product performance

Materials and manufacturing processes share a common purpose of enabling the pharmaceutical product to perform as intended. This review on the role of polymeric materials in additive manufacturing of oral dosage forms, focuses on the interface between the polymer and key stages of the additive manufacturing process, which determine printability. By systematically clarifying and comparing polymer functional roles and properties for a variety of AM technologies, together with current and emerging techniques to characterize these properties, suggestions are provided to stimulate the use of readily available and sometimes underutilized pharmaceutical polymers in additive manufacturing. We point to emerging characterization techniques and digital tools, which can be harnessed to manage existing trade-offs between the role of polymers in printer compatibility versus product performance. In a rapidly evolving technological space, this serves to trigger the continued development of 3D printers to suit a broader variety of polymers for widespread applications of pharmaceutical additive manufacturing.

Predicting Drug Release from 3D Printed Oral Medicines Based on the Surface Area to Volume Ratio of Tablet Geometry

3D printing offers the advantage of being able to modify dosage form geometry, which can be exploited to modify release characteristics. In this study, we investigated the influence of the surface area to volume ratio (SA/V) to change and predict release profiles of 3D printed dosage forms. Geometries with varying SA/V and dosages were designed and printed, and drug dissolution was investigated. Three drug substances were used: pramipexole, levodopa (both BCS I) and praziquantel (BCS II). Two polymers were chosen as matrix formers: polyvinyl alcohol (water-soluble) and ethylene vinyl acetate (inert). Drug release was characterized using the mean dissolution time (MDT) and established equations that describe complete dissolution curves were applied. Predictions were validated with previously un-printed dosage forms. Based on an identified MDT-SA/V correlation, the MDT can be predicted with a deviation of ≤5 min for a given SA/V. Using correlations of fit parameters and SA/V, RMSEP values of 0.6-2.8% and 1.6-3.4% were obtained for the BCS I formulations and RMSEP values of 1.0-3.8% were obtained for the BCS II formulation, indicating accurate prediction over a wide range of dissolution profiles. With this approach, MDT and release profiles of dosage forms with a given SA/V can be precisely predicted without performing dissolution tests and vice versa, the required SA/V can be predicted for a desired release profile.

Selective Laser Sintering (SLS), a New Chapter in the Production of Solid Oral Forms (SOFs) by 3D Printing

3D printing is a new emerging technology in the pharmaceutical manufacturing landscape. Its potential advantages for personalized medicine have been widely explored and commented on in the literature over recent years. More recently, the selective laser sintering (SLS) technique has been investigated for oral drug-delivery applications. Thus, this article reviews the work that has been conducted on SLS 3D printing for the preparation of solid oral forms (SOFs) from 2017 to 2020 and discusses the opportunities and challenges for this state-of-the-art technology in precision medicine. Overall, the 14 research articles reviewed report the use of SLS printers equipped with a blue diode laser (445-450 nm). The review highlights that the printability of pharmaceutical materials, although an important aspect for understanding the sintering process has only been properly explored in one article. The modulation of the porosity of printed materials appears to be the most interesting outcome of this technology for pharmaceutical applications. Generally, SLS shows great potential to improve compliance within fragile populations. The inclusion of "Quality by Design" tools in studies could facilitate the deployment of SLS in clinical practice, particularly where Good Manufacturing Practices (GMPs) for 3D-printing processes do not currently exist. Nevertheless, drug stability and powder recycling remain particularly challenging in SLS. These hurdles could be overcome by collaboration between pharmaceutical industries and compounding pharmacies.

Disrupting 3D printing of medicines with machine learning

3D printing (3DP) is a progressive technology capable of transforming pharmaceutical development. However, despite its promising advantages, its transition into clinical settings remains slow. To make the vital leap to mainstream clinical practice and improve patient care, 3DP must harness modern technologies. Machine learning (ML), an influential branch of artificial intelligence, may be a key partner for 3DP. Together, 3DP and ML can utilise intelligence based on human learning to accelerate drug product development, ensure stringent quality control (QC), and inspire innovative dosage-form design. With ML's capabilities, streamlined 3DP drug delivery could mark the next era of personalised medicine. This review details how ML can be applied to elevate the 3DP of pharmaceuticals and importantly, how it can expedite 3DP's integration into mainstream healthcare.

Controlling drug release with additive manufacturing-based solutions

3D printing is an innovative manufacturing technology with great potential to revolutionise solid dosage forms. Novel features of 3D printing technology confer advantage over conventional solid dosage form manufacturing technologies, including rapid prototyping and an unparalleled capability to fabricate complex geometries with spatially separated conformations. Such a novel technology could transform the pharmaceutical industry, enabling the production of highly personalised dosage forms with well-defined release profiles. In this work, we review the current state of the art of using additive manufacturing for predicting and understanding drug release from 3D printed novel structures. Furthermore, we describe a wide spectrum of 3D printing technologies, materials, procedure, and processing parameters used to fabricate fundamentally different matrices with different drug releases. The different methods to manipulate drug release patterns including the surface area-to-mass ratio, infill pattern, geometry, and composition, are critically evaluated. Moreover, the drug release mechanisms and models that could aid exploiting the release profile are also covered. Finally, this review also covers the design opportunities alongside the technical and regulatory challenges that these rapidly evolving technologies present.

Direct Powder Extrusion of Paracetamol Loaded Mixtures for 3D Printed Pharmaceutics for Personalized Medicine via Low Temperature Thermal Processing

Three-dimensional printed drug development is nowadays an active area in the pharmaceutical industry, where the search for an appropriate edible carrier that permits the thermal processing of the mixture at temperature levels that are safe for the drug is an important field of study. Here, potato starch and hydroxypropyl cellulose based mixtures loaded with paracetamol up to 50% in weight were processed by hot melt extrusion at 85 °C to test their suitability to be thermally processed. The extruded mixtures were tested by liquid chromatography to analyze their release curves and were thermally characterized. The drug recovery was observed to be highly dependent on the initial moisture level of the mixture, the samples being prepared with an addition of water at a ratio of 3% in weight proportional to the starch amount, highly soluble and easy to extrude. The release curves showed a slow and steady drug liberation compared to a commercially available paracetamol tablet, reaching the 100% of recovery at 60 min. The samples aged for 6 weeks showed slower drug release curves compared to fresh samples, this effect being attributable to the loss of moisture. The paracetamol loaded mixture in powder form was used to print pills with different sizes and geometries in a fused deposition modelling three-dimensional printer modified with a commercially available powder extrusion head, showing the potential of this formulation for use in personalized medicine.