ABSTRACT
Eye drops and ointments have been used in ophthalmology for a long time. The drugs contained in them are absorbed mainly by the cornea, and the absorption depends on the length of contact. Aqueous solutions are washed from the cornea in 5 to 6 min. Ointments, due to the greater viscosity of the base, remain much longer, but ointment films blur the vision. Increased viscosity may, however, cause pain and block the lacrimal ducts, therefore viscosity should not exceed 30 mPa • sec. The number of drugs that can be administered in a transdermal therapeutic system is limited to those whose dosage does not exceed 1 to 2 mg per day, are not skin irritants, and possess the right physiochemical properties to allow the partition into the stratus corneum and permeation through the epidermis and dermis to the capillary system.
