Inkjet printing of paracetamol and indomethacin using electromagnetic technology: Rheological compatibility and polymorphic selectivity

Drop-on-demand inkjet printing is a potential enabling technology both for continuous manufacturing of pharmaceuticals and for personalized medicine, but its use is often restricted to low-viscosity solutions and nano-suspensions. In the present study, a robust electromagnetic (valvejet) inkjet technology has been successfully applied to deposit prototype dosage forms from solutions with a wide range of viscosities, and from suspensions with particle sizes exceeding 2 μm. A detailed solid-state study of paracetamol, printed from a solution ink on hydroxypropyl methylcellulose (HPMC), revealed that the morphology of the substrate and its chemical interactions can have a considerable influence on polymorphic selectivity. Paracetamol ink crystallized exclusively into form II when printed on a smooth polyethylene terephthalate substrate, and exclusively into form I when in sufficient proximity to the rough surface of the HPMC substrate to be influenced by confinement in pores and chemical interactions. The relative standard deviation in the strength of the dosage forms was