Controlled release and ocular absorption of tilisolol utilizing ophthalmic insert-incorporated lipophilic prodrugs

To control ocular drug delivery, the O-butyryl ester prodrug of tilisolol (BUTL) and the O-palmitoyl ester prodrug of tilisolol (PalTL) were incorporated into an ophthalmic insert. The released TL from BUTL inserts and PalTL inserts in pH 7.4 phosphate-buffered saline until 5 h were approximately 25% and 3% of that from TL inserts, respectively. In addition, BUTL was also released from BUTL inserts. However, PalTL was not released from the PalTL insert. The release of drugs from TL inserts and BUTL inserts was little affected by the addition of bovine serum albumin (BSA) in pH 7.4 phosphate-buffered saline. In contrast, the release of drugs from PalTL inserts were enhanced by the addition of BSA. After application of TL, BUTL, and PalTL inserts to the rabbit eye, the aqueous humor concentration of TL was prolonged compared with TL instillation, and the plasma concentration of TL was much lower than that of TL instillation. The ratios of the area under the TL concentration-time curve (AUC) in the aqueous humor to AUC in the plasma (AUC(aqueous)/AUC(plasma)) after application of BUTL until 8 h were 3.1-fold and 3.8-fold higher than those of the TL insert and PalTL insert, respectively.