In short
Chloramphenicol is an antibiotic used to treat serious bacterial infections, including chronic suppurative otitis media (CSOM), a long-lasting infection of the middle ear that causes ear discharge. One Phase 3 clinical trial is currently authorised to compare topical chloramphenicol ear drops with topical ciprofloxacin ear drops in 88 adults with CSOM. The trial measures whether chloramphenicol is non-inferior to ciprofloxacin in resolving ear discharge (otorrhoea) by Day 14.
Key points
- Chloramphenicol is an antibiotic reserved for serious infections when safer antibiotics are not suitable.
- A Phase 3 trial is testing chloramphenicol ear drops against ciprofloxacin ear drops in adults with chronic suppurative otitis media (CSOM).
- The trial plans to enrol 88 participants and is currently authorised.
- The main outcome is complete resolution of ear discharge at Day 14, checked by otoscopy or endoscopy.
- Chloramphenicol can cause serious blood disorders, including aplastic anaemia, and is given by injection only in hospital settings.
What is chloramphenicol?
Chloramphenicol is an antibiotic that is clinically useful for, and should be reserved for, serious infections caused by organisms susceptible to its antimicrobial effects when less potentially hazardous therapeutic agents are ineffective or contraindicated. It is available as chloramphenicol sodium succinate for injection, a powder that is dissolved before being given intravenously. In the United Kingdom, chloramphenicol is also known under the brand name Optrex when used for eye infections. The NHS describes chloramphenicol as an antibiotic used to treat bacterial infections, particularly eye and ear infections.
How does chloramphenicol work?
Chloramphenicol works by interfering with the ability of bacteria to make proteins, which they need to grow and multiply. Recent structural research has examined how chloramphenicol inhibits bacterial protein production in a context-dependent manner, providing insight into its mechanism of action at the molecular level. By blocking this process, chloramphenicol stops bacteria from spreading, allowing the body's immune system to clear the infection.
Which conditions is chloramphenicol used or studied for?
- Chronic suppurative otitis media (CSOM) – a long-lasting middle ear infection with persistent ear discharge. A Phase 3 trial is testing chloramphenicol ear drops for this condition.
- Eye infections – chloramphenicol is used to treat bacterial eye infections, including conjunctivitis.
- Ear infections – chloramphenicol is also used for certain bacterial ear infections.
- Serious systemic infections – the injectable form is reserved for serious infections when less hazardous antibiotics are ineffective or contraindicated.
How is chloramphenicol given?
Chloramphenicol is available in different forms. The injectable form, chloramphenicol sodium succinate, is given intravenously and is intended for intravenous use only; it has been demonstrated to be ineffective when given intramuscularly. Topical forms include eye drops and ear drops. In the clinical trial for CSOM, chloramphenicol is given as a 2 mg auricular (ear) solution. The NHS also describes chloramphenicol eye drops for treating eye infections.
What do the clinical trials show?
One Phase 3 clinical trial is currently authorised to investigate chloramphenicol in adults with chronic suppurative otitis media (CSOM). The trial plans to enrol 88 participants and compare topical chloramphenicol (2 mg ear drops) with topical ciprofloxacin (1.2 mg ear drops). The primary outcome is the proportion of patients with complete resolution of otorrhoea at Day 14, assessed by otoscopy or endoscopy performed by at least two otolaryngologists with digital photographic records. The study aims to evaluate whether chloramphenicol is non-inferior to ciprofloxacin in resolving ear discharge in adult patients with CSOM.
What side effects are known?
Chloramphenicol carries a serious safety warning. Serious and fatal blood disorders, including aplastic anaemia, hypoplastic anaemia, thrombocytopenia and granulocytopenia, are known to occur after the administration of chloramphenicol. There have also been reports of aplastic anaemia attributed to chloramphenicol which later terminated in leukaemia. Blood disorders have occurred after both short-term and prolonged therapy with this drug. Because of these risks, chloramphenicol must not be used when less potentially dangerous agents will be effective, and it must not be used for trivial infections such as colds, influenza or throat infections, or as a preventive agent. During treatment, it is essential that adequate blood studies be made, and patients are preferably hospitalised to allow appropriate monitoring.