3-dimensional printing (3DP) of medicines is becoming an increasingly popular trend, especially since the first 3D printed medicine (Spritam®) was approved by the FDA in August 2015.
Researchers from University College London – School of Pharmacy and FabRx Ltd. have recently published a paper in International Journal of Pharmaceutics in which they show, for the first time, the fabrication of oral tablets by stereolithography.
Graphical abstract of the article.
Stereolithography (SLA) is a type of 3DP technology, based on the solidification of a liquid resin by photopolymerization. A laser is focused on to a specific depth in a vat of resin, causing localized polymerization (and so solidification). Solidification is repeated in a layer by layer manner until a solid, 3D object is produced. SLA is superior to other 3DP techniques in terms of resolution.
In a previous study, approximately 50% of the model drug 4-aminosalicylic acid (4-ASA) was degraded during 3D printing.
In this study, paracetamol (called acetaminophen in US) and 4-aminosalicylic acid (4-ASA, used in the treatment of inflammatory bowel diseases) were selected as model drugs. The drugs were added to the solution of monomers and the resulting photopolymer solution was loaded into the 3D printer, a commercial Form 1+ SLA 3D printer (Formlabs Inc, USA).
Form 1+ SLA 3D printer
A torus design (donut shape) was selected as the template to print the tablets due to its complexity compared with conventional tablets shapes, and because of its difficulty in manufacture by current production techniques, such as powder compaction.
Template used as a model for printing tablets
Tablets containing the drugs were successfully produced with the SLA printer and various formulations with different properties were fabricated. No drug was degraded during the 3D printing process what is especially relevant for 4-ASA since its degradation using FDM 3D printing has been previously reported. A major advantage of SLA printing is its versatility, as drugs can be mixed with the photopolymer solution prior to printing, and become trapped in the solidified matrices. Other advantages over FDM 3DP is that the printing is a one-step method, without need of previous processes, just dissolution of the drug in the printing solution.
3DP tablets loaded with 4-ASA (brown colour) and paracetamol (white colour).
The in vitro dissolution test performed in a realistic dynamic dissolution simulation of the gastrointestinal tract shows that drug release from the tablets commences in the gastric phase and continues during the intestinal phase for all formulations and it was dependent on the composition of the formulations.
According to the authors, this technology offers a simple, fast method to fabricate drug-loaded tablets with high resolution. Compared with FDM 3D printing, SLA printing reduces drug degradation and so offers an alternative route to produce tablets incorporating thermo-sensitive drugs.
SLA 3DP technology may allow the manufacture of drug loaded tablets with specific extended-release profiles. In the future this technology could become a manufacturing technology for the elaboration of oral dosage forms, for industrial production or even for personalised dose.