# Therapeutic Hydrogel Lenses and the Antibacterial and Antibiotic Drugs Release
## 4 Discussion  
The obtained results indicate that passage through the lens affects the quantity of anti-inflammatory drugs, whether steroidal or nonsteroidal. Conversely, lens passage does not affect the antibacterial efficacy of the antibiotic chloramphenicol. These findings bear clinical relevance because therapeutic contact lenses are an option to treat ocular diseases due to their ability to release drugs for extended periods of time. Therefore, critical lens properties such as water content and ion and oxygen permeability for comfortable day and night wear contact lenses are important topics of research to enable their therapeutic use. We evaluated the interaction between different types of drugs and hydrogel therapeutic lenses. The lenses evaluated in this study are of two different types: ionic and nonionic. The Contaflex 75% nonionic hydrogel lens with 75% water is a type of lens in which the water content is ideally suited to bandaging and other therapeutic lens applications. Hydration of these materials is best performed in buffered saline with a pH of 6.8-7.3. G72 HW ionic hydrogel lenses, including G-4X, G-5X and Ultra O\({}_{2}\), have 72% water content and a refractive index of 1.384, and they meet the criteria for high-performance daily-wear lenses. We analyzed the interaction of four eye drop formulas, including three different anti-inflammatory drugs and one antibiotic, with therapeutic lenses under different conditions and at different times. Silicone hydrogel materials for daily-wear lenses should be supported by sound clinical data]. We measured the volume-normalized areas of the peaks of nonsteroidal anti-inflammatory drugs (NSAIDs), corticosteroids, and antibiotics commonly used in ocular therapy. In our experiment, we verified for all the analysis times considered (after 30 min, 60 min, 2 h and 24 h) that then G72 HW ionic hydrogel lens released a different quantity of eye drops than the Contaflex 75% nonionic hydrogel lens or the balafilcon A silicone hydrogel lens. Hydrogels have proven to be an extremely versatile class of materials with many potential applications in ophthalmology. Indeed, they are widely applied as soft contact lenses and foldable intraocular lenses [20]. Figure 4: Inhibition of _Salmonella typhimurium_ growth by chloramphenicol after interaction with different lens types. Inhibition effectiveness was measured according to the diameter of the zone of inhibition. The results of the present study highlight the relevance of adapting lenses to the ongoing therapy administered to each patient to allow a personalized medical approach. Furthermore, our findings emphasize the importance of using hydrogel material to minimize the modification of drug efficacy by the contact lens. Our results provide evidence that the ionic lens (G72 HW) is more effective than other lenses in releasing steroidal and nonsteroidal anti-inflammatory drugs and the antibiotic tested. This result is amenable to the electric charge of the ionic hydrogel. The presence of similar electrical polarities on both lenses and drugs causes reciprocal repulsion decreasing the amount of drugs entrapped inside the hydrogel and increasing the amount of drug released. This situation is well detectable for chloramphenicol but less evident for anti-inflammatory drugs. Indeed, the hydrogel ionic lens provides a better release than other lenses for bethamethone while differences from other lenses, although present, are less evident for bromophenac and dexamethasone. It is likely that the differences observed in the interactions between different anti-inflammatory drugs and the hydrogel ionic lens are due to differences in the electric charges of the anti-inflammatory drugs tested. HPLC gradient analyses demonstrate differences in the amount of chloramphenicol released from different lenses. However, the dimension of the bacterial inhibition-growth haloes was similar for all three lens types.