Printing T3 and T4 oral drug combinations as a novel strategy for hypothyroidism

Hypothyroidism is a chronic and debilitating disease that is estimated to affect 3% of the general population. Clinical experience has highlighted the synergistic value of combining triiodothyronine (T ₃) and thyroxine (T ₄) for persistent or recurrent symptoms. However, thus far a platform that enables the simultaneous and independent dosing of more than one drug for oral administration has not been developed. Thermal inkjet (TIJ) 2D printing is a potential solution to enable the dual deposition of T ₃ and T ₄ onto orodispersible films (ODFs) for therapy personalisation. In this study, a two-cartridge TIJ printer was modified such that it could print separate solutions of T ₃ and T ₄. Dose adjustments were achieved by printing solutions adjacent to each other, enabling therapeutic T ₃ (15–50 μg) and T ₄ dosages (60–180 μg) to be successfully printed. Excellent linearity was observed between the theoretical and measured dose for both T ₃ and T ₄ (R ² = 0.982 and 0.985, respectively) by changing the length of the print objective (Y-value). Rapid disintegration of the ODFs was achieved (<45 s). As such, this study for the first time demonstrates the ability to produce personalised dose combinations by TIJ printing T ₃ and T ₄ onto the same substrate for oral administration.