**3. Advantages of novel over conventional topical ophthalmic drug delivery systems**

The delivery of ophthalmic drugs is one of the most difficult tasks confronting pharmaceutical researchers. Their target is to achieve and maintain a therapeutic level at the action site for a long time. To keep medication levels at the target site for an extended period of time, novel drug delivery methods should be created. In terms of distinct delivery methods or tools to be used before, during, or after administration, novel drug delivery systems are fresh on the market and variations on earlier ones. Existing remedies are becoming ineffective as a result of the development of new technology. By decreasing drug exposure to non-target cells and increasing the amount and durability of a drug around target cells, new drug delivery methods improve a drug's therapeutic effects while minimising its harmful consequences [37]. One of the most difficult delivery methods for pharmaceutical researchers is ophthalmic medication delivery [38]. Traditional delivery methods like suspensions, solutions, emulsions, intravitreal injections, and ointments have poor ocular bioavailability, or less than 1%, as a result of various factors including fast yield, low absorption, short residence time in the cul-de-sac, and relatively impermeable drugs [39]. Within 5 minutes of administration, up to 80% of the administered dose may be lost due to tears and nasolachrymal drainage. **Figure 1** illustrates the difference between conventional and novel drug delivery systems.

The use of viscosity enhancers, ophthalmic solutions in which the drug dissolves slowly, or ophthalmic inserts can all be used to extend the duration of therapy [37]. Because it prolongs drug release and allows for greater contact with the front of the eye, ophthalmic drug administration is optimal [38]. Novel ocular drug administration aims to prolong medicine retention duration in the eye or facilitate transcorneal drug penetration to boost drug bioavailability [40]. From eye drops to ophthalmic iontophoresis, in situ gels, dendrimers, ocular inserts mucoadhesive polymers, penetration enhancers, mucoadhesive polymers, hydrogels, and targeted drug delivery systems, topical ocular medication delivery has been enhanced [41]. Most frequently available ophthalmic preparations are eye drops and ointments. Nonetheless, due to tear flow and lachrymal nasal drainage, these preparations are rapidly drained away from the ocular cavity when instilled into the cul-de-sac. Because only a small amount is available for therapeutic effect, frequent dosing is required. Over the past three

*Novel Topical Drug Delivery Systems in Ophthalmic Applications DOI: http://dx.doi.org/10.5772/intechopen.108915*

**Figure 1.**

*Advantages of novel drug delivery systems over conventional systems in ophthalmic applications.*

decades, newer pharmaceutical ophthalmic formulations have been created to address these problems. These formulations include in situ gel, nanoparticle, liposome, nanosuspension, microemulsion, iontophoresis, and ocular inserts [42].
