Hyperthermia and temperature-sensitive liposomes: selective delivery of drugs into the eye

Experiments were performed to quantitate the delivery of two drugs into the eye following hyperthermia. The drugs, cytosine arabinoside and 5-fluorouridine, were encapsulated in temperature-sensitive liposomes. After systemic injection of the liposome-encapsulated drug, microwave hyperthermia was applied to the superior limbus of rabbit eyes in an attempt to locally release the drug. Samples of aqueous humor and vitreous showed significantly higher drug levels in the heated versus the unheated eyes. Histology of the heated eyes showed no significant damage to ocular structures at the power level used to release the entrapped drug. Heating at higher power levels did damage the eye, confirming earlier studies. The potential uses and limitations of this drug delivery modality are discussed.