Pharmacotherapeutic group: corticosteroids and anti-infectives in combination, ATC code: S01CA01.
Dexamethasone:
The anti-inflammatory potency of dexamethasone is approximately 25 times that of hydrocortisone. Like all anti-inflammatory corticosteroids, it inhibits phospholipase A2, the first step in prostaglandin synthesis, thereby preventing the formation of inflammatory mediators such as prostaglandins and leukotrienes. Dexamethasone additionally inhibits the chemotactic migration of neutrophils to the site of inflammation and reduces leukocyte numbers and activity.
Chloramphenicol:
Chloramphenicol is a low-molecular-weight bacteriostatic antibiotic with a broad spectrum of activity. It is effective against gram-positive and gram-negative bacteria, rickettsiae, and mycoplasmas. Its mechanism of action consists in the selective inhibition of bacterial protein synthesis.
Chloramphenicol is active against the following ocular pathogens: Staphylococcus aureus, streptococci including Streptococcus pneumoniae, Escherichia coli, Haemophilus influenzae, Klebsiella/Enterobacter species, Moraxella lacunata (Morax-Axenfeld bacillus), and Neisseria species. It is not sufficiently active against Pseudomonas aeruginosa or Serratia marcescens.
Resistance to chloramphenicol has been demonstrated both in vitro and in vivo in strains of Staphylococcus, Salmonella, Shigella, E. coli, and Pseudomonas aeruginosa. Resistance is in part mediated by a plasmid-borne resistance factor. In vitro susceptibility testing of bacteria isolated from the ocular surface in patients with clinical signs of infection, using various topical antibiotics, has shown that chloramphenicol exhibits the highest in vitro activity among the antibiotics tested and that resistance to chloramphenicol was the lowest.
⚠️ Warnings
Prolonged treatment with chloramphenicol, including topical ocular administration, may in very rare cases lead to bone marrow aplasia. The irreversible form may appear after a latent period of weeks or months.
The use of chloramphenicol is associated with a potential risk of aplastic anaemia or other blood dyscrasias. The product should be used only when alternative forms of therapy are ineffective and/or contraindicated.
Prolonged use may give rise to secondary ocular infections or favour the development of resistant bacteria. Corticosteroids may mask, induce, or exacerbate ocular infection.
Long-term use of corticosteroids may cause a pathological increase in intraocular pressure. In predisposed patients and those with glaucoma, intraocular pressure should be monitored regularly, particularly in the case of long-term treatment.
Intensive, prolonged treatment may contribute to the onset or worsening of posterior subcapsular cataract. The product should not be used for longer than 10 days unless otherwise directed by the physician.
In conditions causing thinning of the cornea or sclera, chronic use of corticosteroids is known to be capable of causing perforation. Caution is also required when topical corticosteroids such as dexamethasone are used concomitantly with topical NSAIDs (non-steroidal anti-inflammatory drugs) (see section 4.5).
If no improvement is observed after three days of treatment, alternative treatment options should be considered.
The use of corticosteroids following cataract surgery may delay healing and increase the incidence of cyst formation.
Particular caution is required in patients with diabetes mellitus. These patients may be predisposed to elevated intraocular pressure and/or cataract formation.
In general, caution is required when administering corticosteroids to infants (aged 28 days to 3 months) and children under 2 years of age.
In predisposed patients, including children and patients receiving CYP3A4 inhibitors (including ritonavir and cobicistat), Cushing's syndrome and/or adrenal suppression associated with systemic absorption of ophthalmic dexamethasone may occur after intensive or prolonged continuous treatment. In such cases, treatment should be gradually discontinued.
Visual disturbances
Visual disturbances may be reported with systemic and topical corticosteroid use. If a patient presents with symptoms such as blurred vision or other visual disturbances, referral to an ophthalmologist should be considered for evaluation of possible causes, which may include cataract, glaucoma, or rare conditions such as central serous chorioretinopathy (CSCR), which has been reported following the use of systemic and topical corticosteroids.
The use of contact lenses during ocular infection is not recommended, as it may promote the spread of microorganisms.
The eye drops are not intended for injection. They must never be administered subconjunctivally or directly into the anterior chamber of the eye.
Discontinuation of treatment after long-term use should be carried out gradually, as for systemically administered corticosteroids.
