Ophthalmic formulations solution drainage

To enhance corneal drug absorption, the tear film concentration can be prolonged by manually blocking the nasolacrimal ducts or by tilting the head back to reduce drainage (see Chapter 3). Another effective technique to increase corneal penetration is to administer a series of ophthalmic solutions at intervals of approximately 10 minutes. It has been determined, however, that when different drug formulations are given as drops in rapid succession, the medications first applied are diluted and do not achieve fiill therapeutic potential. 

Drugs are normally applied to the eye as solutions (eye drops) and more rarely as suspensions or as ointments. However, the loss of drug either by tear flow or by drainage into the nasolacrimal duct as well as the impairment of vision by viscous ophthalmic ointments are major drawbacks for optimum delivery. As a submicron emulsion is biologically compatible, stable, and sterilizable, it appeared to be of imere.st as an ocular vehicle. Emulsion formulations have some advantages in providing a reservoir for slow release of drug in a nonviscous medium. 

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