3D printed sex-specific medicines: Excipient-mediated modulation boosts systemic drug exposure by more than three-fold in male rats.

Excipients, historically regarded as inert, are now being recognised for their ability to actively modulate biological targets, including intestinal efflux transporters such as P-glycoprotein (P-gp). We have previously shown that polyethylene glycol (PEG) excipients can selectively enhance the oral bioavailability of P-gp substrate drugs, particularly in males. This study examined how 3D printed formulations containing PEG 2000 influence the pharmacokinetics of silodosin, a P-gp substrate drug used for the treatment of benign prostatic hyperplasia in ageing men, using male and female Wistar rats. Initial concentration screening studies with aqueous solutions revealed that a 1 % w/v PEG 2000 concentration (corresponding to 5 mg) maximally increased silodosin systemic exposure by 36 % compared to the control in males, with no significant effect in females, confirming sex-specific pharmacokinetic modulation. To exploit this unique phenomenon, 5 mg of PEG 2000 was incorporated as a functional excipient into silodosin-loaded printlets (3D printed tablets) fabricated via direct powder extrusion. The printlets achieved complete drug release within 70 min, exhibiting highly similar dissolution profiles between test and control formulations (f2 = 88.6). In vivo pharmacokinetic studies revealed that printlets containing PEG 2000 resulted in a 213 % increase in plasma exposure in males relative to the control, while no significant enhancement was observed in females. By integrating biological variables such as sex into formulation design and leveraging the promising potential of 3D printing, this study demonstrates for the first time how excipient functionality can be harnessed to develop sex-specific oral therapies and advance personalised oral drug delivery. These findings pave the way for the future clinical translation of sex- and excipient-driven therapeutic approaches.