Chloramphenicol
Is It Right for You?
A complete guide to Chloramphenicol — what it treats, how it works, dosages, side effects, and when a clinician may prescribe it following an online consultation.
What Is Chloramphenicol?
Chloramphenicol is a broad-spectrum antibiotic available topically for ophthalmic (eye) use in the UK as 0.5% eye drops and 1% eye ointment. It is one of the most widely used ophthalmic antibiotics in UK primary care and is available both on prescription and — uniquely among antibiotic eye preparations — over the counter for adults and children aged 2 years and over from pharmacies, for the treatment of acute bacterial conjunctivitis.
Chloramphenicol was first isolated from Streptomyces venezuelae in 1947 and has been in clinical use since the late 1940s. Systemically, chloramphenicol is rarely used today in the UK due to the risk of serious haematological toxicity (aplastic anaemia) with oral and intravenous formulations. However, topical ophthalmic chloramphenicol achieves very high local concentrations in ocular tissues with negligible systemic absorption, making it highly effective for superficial eye infections while avoiding the haematological risks associated with systemic use.
What Conditions Does Chloramphenicol Treat?
Chloramphenicol is prescribed for:
The primary and almost exclusive indication for chloramphenicol eye drops and ointment in UK primary care is acute bacterial conjunctivitis — superficial infection of the conjunctiva (the thin, transparent membrane covering the white of the eye and inner eyelids). Bacterial conjunctivitis presents with redness, discharge (typically mucopurulent — thick, yellow-green), crusting of the eyelid margins particularly on waking, and mild irritation or grittiness. Common causative organisms include Staphylococcus aureus, Streptococcus pneumoniae, Haemophilus influenzae, and Moraxella catarrhalis.
It is important to distinguish bacterial conjunctivitis from viral conjunctivitis (the more common form, typically associated with clear watery discharge, recent upper respiratory tract infection, and lymphadenopathy) and allergic conjunctivitis (itching predominates, bilateral, seasonal). Chloramphenicol is only appropriate for bacterial conjunctivitis and has no efficacy against viral or allergic causes.
NICE guidance notes that acute infective conjunctivitis is usually self-limiting within 7–14 days without treatment. Antibiotic eye drops modestly shorten the duration of symptoms and increase the proportion of patients who are clinically and bacteriologically cured at day 5–7. Clinical judgement is required on whether to treat immediately or provide a safety-net prescription for delayed use.
Chloramphenicol may also be used for blepharitis (eyelid margin infection), corneal ulcer prophylaxis or adjunctive treatment, and post-operative prophylaxis of superficial ocular bacterial infection — though these indications are more commonly managed in specialist ophthalmological settings.
While Chloramphenicol is effective for managing bacterial conjunctivitis, it should be used cautiously in patients with a known hypersensitivity to the drug.
How Does Chloramphenicol Work?
Chloramphenicol inhibits bacterial protein synthesis by binding to the 50S ribosomal subunit at the peptidyl transferase centre, blocking the formation of peptide bonds between amino acids during translation. This prevents elongation of the growing polypeptide chain, halting protein synthesis. The mechanism is shared with clindamycin and linezolid, and chloramphenicol therefore competitively inhibits these drugs if used concurrently.
Chloramphenicol is bacteriostatic against most organisms but bactericidal against specific pathogens including Streptococcus pneumoniae and Haemophilus influenzae. Its broad spectrum encompasses Gram-positive cocci (S. aureus, S. pneumoniae, S. pyogenes), Gram-negative organisms (H. influenzae, M. catarrhalis, Neisseria gonorrhoeae), anaerobes, Chlamydia, Rickettsia, and some other intracellular pathogens.
When applied topically to the eye, chloramphenicol achieves therapeutic concentrations throughout the conjunctiva, cornea, and aqueous humour, while systemic absorption from the conjunctival surface is minimal — typically below the level of detection in plasma with standard dosing.
Dosages & Administration
The correct dose depends on the type and severity of infection, age, weight, and kidney function. Always follow your clinician's instructions. The table below is for general reference only.
Administration Tips
Always follow your clinician's instructions. For 0.5% eye drops, instill 1–2 drops into the affected eye(s) every 2 hours while awake for 48 hours; then reduce to 4 times daily for a total of 5–7 days. For 1% eye ointment, apply approximately a 1 cm ribbon to the inner lower eyelid three to four times daily for 5–7 days. A combined regimen of drops during the day and ointment at night is also effective.
Side Effects of Chloramphenicol
Chloramphenicol is generally well tolerated, but some side effects may occur.
- Transient stinging or burning on instillation
- Temporary blurred vision
- Local hypersensitivity reaction
- Aplastic anaemia — a rare but serious condition associated with systemic use.
Patients should be informed about the risk of allergic reactions and the importance of not using Chloramphenicol for unconfirmed infections.
Drug Interactions
Topical ophthalmic chloramphenicol has negligible systemic absorption. Clinically significant systemic drug interactions are not expected or documented for ophthalmic preparations. Local interactions of note:
Important Warnings
Never share chloramphenicol eye drops or ointment between individuals. Shared bottles are a significant source of cross-infection. Each person requires their own bottle.
Remove soft contact lenses before applying chloramphenicol drops. Do not replace for at least 15–20 minutes. Do not wear contact lenses during active conjunctivitis — this prolongs infection and increases the risk of corneal complications.
Eye drops that have been open for more than 28 days must be discarded, even if unused portions remain. Opened drops are at risk of contamination and infection from environmental organisms.
You develop eye pain (beyond mild grittiness), photophobia (light sensitivity), significant reduction in vision, a corneal whitish opacity, or symptoms that worsen despite treatment. These may indicate corneal involvement or a more serious condition requiring specialist care.
Speak to a Clinician About Treatment
Getting advice no longer means sitting in a waiting room. Through The GP Service, you can consult with a licensed clinician in minutes — from home, on your lunch break, or wherever works for you. If treatment is clinically appropriate, your clinician can issue a prescription during the consultation. A consultation does not guarantee a prescription.
The treatment you need, when you need it.
Chloramphenicol FAQs
Acute bacterial conjunctivitis is usually self-limiting within 7–14 days without treatment. Antibiotic eye drops shorten the duration of symptoms by approximately 2–3 days and modestly increase the likelihood of clinical and bacteriological cure. Treatment is typically recommended for patient comfort, to reduce the period of contagiousness, and to prevent spread to the other eye or to other individuals. In mild cases, a watchful waiting approach with hygiene measures (frequent handwashing, not sharing towels) is a reasonable alternative.
No. Eye drops opened more than 28 days ago must be discarded, regardless of how much remains. Using old, contaminated drops risks introducing a new infection to the eye. If a new episode of conjunctivitis occurs, a fresh bottle should be obtained. Additionally, if leftover drops are from a previous prescription, they may have been stored incorrectly or may have exceeded their shelf life.
With chloramphenicol treatment, most patients with bacterial conjunctivitis see significant improvement within 3–5 days and are fully resolved by day 7. If symptoms are not improving after 5 days of treatment, clinical reassessment is required — the organism may be resistant, the diagnosis may be incorrect (viral or allergic conjunctivitis, or another ocular condition), or there may be a persistent source of infection such as a nasolacrimal duct obstruction.
Over-the-counter chloramphenicol eye drops are licensed for use in children aged 2 years and over. For children under 2 years — including infants and neonates — a clinician should always be consulted before use, as even small amounts of topically absorbed chloramphenicol may be problematic in neonates due to immature drug metabolism.
Eye drops cause temporary blurring of vision lasting a few minutes. Ointment causes more prolonged blurring. Do not drive or operate machinery immediately after application. Wait until vision is fully clear before driving.