Dexamethasone/Netilmicin Fixed Combination effectively reduces Inflammation After Cataract Surgery
Cataract surgery the most common surgical medical procedure performed annually. After cataract extraction, a varying degree of post-surgical inflammation may occur. Although such inflammation is, in most cases, self-limited, the use of antiinflammatory agents can rapidly resolve it and prevents serious complications resulting from uncontrolled inflammations.
Accordingly, the use of topical corticosteroids and/or non-steroidal anti-inflammatory drugs remains the mainstay of post-surgical management of these patients. A recent study funded by the European Society of Cataract and Refractive Surgeons (ESCRS) showed that a combination of a non-steroidal antiinflammatory drugs and dexamethasone reduces the risk for developing cystoid macular oedema after cataract surgery.
Topical antibiotics can be administered either alone or in combination with corticosteroids. Steroid/antibiotic fixed combinations have several advantages over the use of single components, as better compliance, lower costs, and reduction of the potential wash-out effect.
The choice among different products depends on the bacterial susceptibility to the antibiotic and the type and strength of the steroid included in the formulation. A steroid/antibiotic fixed combination containing 1 mg/mL dexamethasone and 3 mg/mL netilmicin exhibits a fast and effective control of ocular inflammation, either post-operative or not.
In a study, Caporossi et al tested a short treatment with such steroid-antibiotic combination in patients who underwent to uncomplicated cataract surgery.
It was an Open-label, randomized, active-controlled, clinical study conducted in 6 sites in Italy; 238 patients were randomized 2:1 to dexamethasone/netilmicin (dexa/net, n=158) or betamethasone/chloramphenicol (beta/chl, n=80). Treatment was started the day of surgery and continued 4 times daily for 7 days.
The primary efficacy parameter was the anterior chamber (AC) flare. The percentage of patients displaying none or mild (ie, only barely detectable) AC flare was defined as "efficacy rate", whereas the percentage of patients showing a decrease of AC flare score from baseline was defined as "percentage of responders". Additional parameters evaluated were AC cells, conjunctival hyperaemia, corneal and lid oedema, symptoms of ocular discomfort, visual acuity, and intraocular pressure. Dexa/net was considered effective if the efficacy rate was not inferior (by means of 97.5% confidence interval) to that of beta/chl.
- After 7 days of treatment, no AC flare was observed in 92.8% (dexa/net) and 92.3% (beta/chl) of patients, whereas no AC cells were observed in 91.5% (dexa/net) and 93.6% (beta/chl) of patients, respectively.
- The "efficacy rate" was 100% in both groups, whereas the "percentage of responders" was 94.1% in the dexa/net and 93.6% in the beta/chl group. The p-value to reject the null hypothesis of inferiority was <0.001.
- Other efficacy parameters confirmed both treatments as highly effective, despite their difference in steroid content (2 mg/mL for beta/chl vs 1 mg/mL for dexa/net).
- IOP and visual acuity at the end of the study were comparable. Two cases of allergic conjunctivitis were considered adverse events and were both related to dexa/net.
Both treatments had a comparable anti-inflammatory efficacy rate despite the double dose of steroid present in beta/ chl. This finding suggests that a short-term treatment with 1 mg/mL dexamethasone is appropriate to manage post-surgical inflammation and that a stronger and extended exposure to steroids is not necessary. This ensured an effective control of post-operative inflammation and, at the same time, reduced the risk of developing corticosteroid-related side effects and can avoid an overuse of antibiotics.
In authors' opinion the main benefit of dexa/net over other available steroid-antibiotic fixed combinations is related to the antibiotic component. Indeed, netilmicin has a wide spectrum activity (which also includes methicillin-resistant strains) and a negligible toxicity for the ocular surface.
Netilmicin is able to sterilize lid margins and conjunctiva when given before cataract surgery. Moreover, the bacterial flora on the ocular surface isolated from patients undergoing cataract surgery is highly susceptible to netilmicin and much less to other antibiotics. Netilmicin is effective on methicillin-resistant S. Aureus (MRSA), methicillin-resistant Coagulase negative Staphylococci (MRCoNS) and MDR Coagulase negative Staphylococci, whereas these microorganisms display a high resistance to fluoroquinolones.
As a potential limitation of the study, AC inflammation was measured, for practical reasons, by slit-lamp examination rather than by a laser flare and cell meter. Even if the scoring system used to measure flare and cells by slit-lamp examination is subjective and semi-quantitative, yet it corresponds to the actual daily routine of practice.
"In summary, a short-term use of dexa/net fixed combination is effective as beta/chl in the control of post-operative inflammation following uncomplicated cataract surgery."
Source: Caporossi et al; Clinical Ophthalmology 2021:15