Methods and compositions are provided for treating an ocular disease in a subject in need thereof by increasing the bioavailability of a drug in the subject's eye. In one aspect, the ocular disease is at least one of diabetic retinopathy, macular degeneration, endopthalmitis, glaucoma, cataracts, ocular herpes. The methods and compositions provided herein include an efflux transporter inhibitor and a drug effective for treating the ocular disease. The efflux transporter inhibitor is effective to reduce the efflux of the drug through at least one of P-glycoprotein (Pgp), breast cancer resistant protein (BCRP), and multidrug resistant associated protein 1-9 (MRP1-9).
