Le epiretinal membranes (ERM), also commonly known as "macular 'puckersare avascular, semi-translucent fibrocellular membranes that form on the inner surface of the retina due to the removal of the vitreous from the retina.
It is a relatively common condition, occurring in about 7% of the population, most commonly in people over the age of 50. I symptoms associated with epiretinal membranes are often quite mild and in some cases patients may be asymptomatic. In some cases, however, it may come to the loss of vision, double vision and metamorphoses, especially when it is the macula. In these cases, the only treatment option is vitrectomy.
The vitrectomy is one of the most frequent ophthalmic surgeries. In the United States, for example, about 225,000 are performed each year. Of these, a portion are vitreoretinal micro-incision surgeries (MIVS). This type of vitreoretinal surgery has a very high success rate and a low risk of complications, with approximately 1 in 100 patients developing retinal detachment and 1 in 2000 developing ainfection after surgery.
In such cases, to control thepost-operative inflammation and prevent bacterial infections, antibiotics and topical anti-inflammatory drugs are usually prescribed. The two pharmacologically active agents can be administered separately, but concomitant administration in a single ophthalmic product has the advantage of overcome the potential effect of washout, which can be observed when multiple drugs are administered, thus enabling better patient compliance.
Benefits of combining corticosteroids and antibiotics
The formulation dexamethasone 0.1%/netilmicin 0.3% (dexa/net) is a fixed combination of steroids and antibiotics commercially available for ophthalmic use. Both ingredients are widely known and used in ophthalmology and have well-documented efficacy and safety.
The dexamethasone is a corticosteroid, while netilmycin is a state-of-the-art aminoglycoside. Numerous clinical trials of dexa/net-based eye drops in patients with external ocular inflammation or undergoing cataract removal surgery have been conducted, as a result of which this formulation has been approved in several countries for the treatment of ocular inflammatory conditions with risk of bacterial infections.
The dexa/net combination has several advantages, mainly related to the antibiotic component and the formulation. Regarding the antibiotic, the netilmicin has broad-spectrum antimicrobial activity and a low level of antibiotic resistance, allowing coverage even of methicillin-resistant (MR) strains (such as MR S. Aureus and coagulase-negative staphylococci).
Overall, the susceptibility of the most common ocular microorganisms to netilmicin is superior to that to tobramycin and comparable to the latest generation of quinolones. Furthermore, netilmicin has negligible toxicity to the conjunctival epithelial cells and human corneals.
The formulation advantage of dexa/net is related to the water solubility of both active ingredients (dexamethasone phosphate and netilmicin sulphate). For this reason, the formulation allows no preservatives to be used and is easily produced in gel or eye drops.
A new gel formulation for the treatment of ocular inflammation after micro-incisional vitreoretinal surgery
A new formulation of the dexa/net combination has recently been developed. It is an eye gel preservative-free, in format single dose, which contains xanthan gum as an enhancer of viscosity, an excipient that does not interfere with the antimicrobial and anti-inflammatory activities of the drug. A recent study has shown that the gel formulation is retained on the ocular surface for longer than ophthalmic solutions, thus confirming that the use of gel allows a longer time between instillations and allows a decrease in the frequency of administration.
In this study, the efficacy, safety and local tolerability of dexa/net-based gel in the management of inflammation after MIVS without suture were evaluated. The dexa/net eye gel was compared with dexamethasone and tobramycin ophthalmic ointment. Both formulations were used as autonomous treatment during the early post-operative phase following vitreoretinal surgery (3 days); thereafter, a combination of eye drops during the day and the viscous formulation before the patient went to bed.
The rationale for the use of the more viscous formulation in the immediate post-operative period is related to an attempt to increase the ocular contact time of the topically administered drug. The results obtained from the study suggest that dexa/net is effective in the post-operative control of surgical inflammation after MIVS without suture and are consistent with data obtained in the treatment of external ocular inflammation and the management of ocular inflammation following cataract surgery.
The signs and symptoms of ocular inflammation (with the exception of cells and flare in the anterior chamber) were effectively reduced during follow-up, irrespective of the treatment assigned. However, a significant difference was observed for inflammation bulbar conjunctivalwhich was the primary efficacy parameter of the study. Indeed, at the end of the study, the percentage of patients with resolution of inflammation of the bulbar conjunctiva in the dexa/net-treated group was significantly higher than in the dexa/tobra-treated group. Furthermore, patients treated with dexa/net experienced significantly milder symptoms.
It has been hypothesised that the instillation of a eyewash ready for use, rather than in suspension form, and the presence of xanthan gum in the formulation of the dexa/net-based gel may confer a peculiar behaviour, which allows greater local tolerability. Finally, no significant safety issues occurred during the entire study.
In conclusion, dexa/net-based gel can effectively reduce post-surgical ocular inflammation following micro-incisional vitreoretinal surgery without suture. In particular, the eye gel formulation may provide additional benefits to patients in terms of local tolerability.
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