Behavior of printable formulations of loperamide and caffeine on different substrates--effect of print density in inkjet printing.

The primary goal of the current work was to study the applicability of precision inkjet printing in fabrication of personalized doses of active pharmaceutical ingredients (APIs). Loperamide hydrochloride (LOP) and caffeine (CAF) were used as model compounds. Different doses of the drugs in a single dosage unit were produced, using a drop-on-demand inkjet printer by varying printing parameters such as the distance between jetted droplets (drop spacing) and the physical dimensions of the printed dosage forms. The behavior of the formulated printable inks for both APIs was investigated on the model substrates, using different analytical tools. The obtained results showed that printed LOP did not recrystallize on any substrates studied, whereas at least partial recrystallization of printed CAF was observed on all carrier surfaces. Flexible doses of both APIs were easily obtained by adjusting the drop spacing of the depositing inks, and the results were relevant with regards to the theoretical content. Adapting the dose by varying physical dimensions of single dosage units was less successful than the approach in which drop spacing was altered. In conclusion, controlled printing technology, by means of adjusting the distance between jetted droplets, offers a means to fabricate dosage forms with individualized doses.