Most eye drops are antibiotics. Using them incorrectly or improperly can easily lead to complications.
Antibiotic-Only Group
 |
Eye drops containing chloramphenicol |
This group includes brands that contain common antibiotics such as chloramphenicol and tetracycline, as well as those with stronger antibiotics like ciprofloxacin and moxifloxacin.
Eye conditions can sometimes exhibit very similar external symptoms but can be caused by different pathogens. It is essential to use specific antibiotics; otherwise, the condition may not improve and could lead to antibiotic-resistant strains. For example, conjunctivitis may cause redness and a gritty sensation in the eyes, but if it is bacterial, chloramphenicol eye drops should be used; if viral, tetracycline ointment is necessary; and if caused by gonorrhea, tetracycline ointment along with penicillin injections is required.
Some antibiotic eye drops can cause local side effects that make the eyes uncomfortable. For example, moxifloxacin eye drops (brand: Vigamox) can reduce vision, cause dry eyes, corneal inflammation, congestion, pain, itching, and subconjunctival hemorrhage. Usually, these side effects are rare (when used at low doses) but occur more frequently (when higher doses are required) and will resolve once the medication is stopped. To alleviate discomfort, it may be necessary to alternate with eye washes that have soothing properties to reduce irritation and provide a pleasant sensation.
When using eye drops, a portion of the antibiotics enters the bloodstream through the eye’s blood vessels, creating a concentration in the plasma that, although not as high as when taken orally at standard treatment doses, can still cause side effects if overdosed or used long-term (beyond 2 weeks). This risk is heightened with medications that have a slow elimination rate. For this reason, it is crucial to use the correct medication, dosage (number of drops), and avoid prolonged use (beyond 2 weeks).
Some medications are more likely to cause systemic effects and typically have clear contraindications. For instance, chloramphenicol eye drops should not be given to newborns or individuals with bone marrow suppression. Ciprofloxacin eye drops should not be used by pregnant or breastfeeding women and children under 12 years old.
Some medications that can cause systemic effects when taken orally but lack complete information for eye drop use are generally recommended with caution. For example, studies on pregnant rats given moxifloxacin at a dose equivalent to 500mg for humans daily (equivalent to 21,000 times the total daily dose of eye drops) showed that it slowed fetal development and bone growth. Thus, it is advised to use it in pregnant individuals only when absolutely necessary or when no alternatives exist, weighing the benefits against the risks.
 |
| Eye examination for appropriate treatment (Photo: TTO) |
While using antibiotic eye drops, if there’s another condition requiring oral or injectable antibiotics, great caution must be exercised to avoid adverse interactions. For instance, when using chloramphenicol eye drops, one should not take or inject gentamicin, tetracycline, cephalosporins, or polymyxins; and when using tetracycline eye drops, one should avoid taking or injecting penicillin.
Some antibiotic eye drops have a broad antibacterial spectrum in laboratory settings, but in clinical practice, they may not be effective against all bacterial strains (due to low antibacterial potency and insufficient local concentration to inhibit bacteria).
If used long-term, these antibiotics may lead to an overgrowth of resistant strains, resulting in secondary infections. For example, moxifloxacin eye drops are indicated for conjunctivitis caused by many types of bacteria, but prolonged use can lead to superinfection, including fungal superinfection. One common side effect of this medication is actually causing conjunctivitis. New-generation antibiotics with broad antibacterial spectra, if treated as universal medications and used for extended periods, are likely to lead to this side effect.
Combination of Antibiotics and Corticosteroids
This group includes medications that combine corticosteroids with antibiotics (such as chlorocid-H containing hydrocortisone and chloramphenicol) or with two or three antibiotics (such as Maxitrol containing dexamethasone, neomycin, and polymyxin).
These medications are convenient as they provide both antibacterial action (from the antibiotics) and anti-inflammatory effects (from the corticosteroids). However, the corticosteroid component reduces the body’s resistance, thereby diminishing the effectiveness of existing antibiotics, worsening the condition, and facilitating secondary infections (including viral and fungal infections), slowing down the wound healing process, increasing intraocular pressure which may progress to glaucoma, causing vision impairment, occasional visual defects, forming posterior subcapsular cataracts, and thinning the sclera leading to globe perforation. Depending on the components and ratio of the combination, each brand has different efficacy and side effects.
Therefore, this type of medication should only be used when the combination with compatible dosages in the product provides sufficient antibacterial effects, and the action of the corticosteroid is limited (for example, used in anterior segment infections) and not widely for all infections or other conditions (such as in cases of severe infections, viral conjunctivitis, fungal infections, or intraocular damage due to tuberculosis or corneal ulcers).
In rural areas, eye drops are often monotonous with limited selection. In urban areas, the abundance of eye drops makes it difficult to choose the right one. Antibiotic eye drops should be used according to a doctor’s prescription. Many individuals, unaware of the significant importance of eye drops and not fully understanding the potential side effects, use antibiotic eye drops indiscriminately, which can easily lead to complications. It is essential to be vigilant about the side effects of antibiotic eye drops.
