chloramphenicol
broad-spectrum antibiotic· Brands: Chloromycetin, Kemicetine, ChloropticIVPOTOP
Mechanism of action
Chloramphenicol binds reversibly to the 50S subunit of the bacterial ribosome, inhibiting peptidyl transferase activity and preventing the transfer of amino acids to growing peptide chains. This blocks protein synthesis and is primarily bacteriostatic, though it can be bactericidal against certain organisms at high concentrations.
Pharmacokinetics
Chloramphenicol is well absorbed orally and reaches therapeutic concentrations in most tissues, including cerebrospinal fluid and the eye. It is extensively metabolised in the liver by glucuronidation, with both the parent drug and inactive metabolites excreted in urine. The half-life is approximately 1.5 to 3.5 hours in adults, but is considerably prolonged in hepatic impairment and in neonates, requiring dose adjustment.
Indications & dosing
Bacterial meningitis (severe, when other antibiotics are contraindicated)
Max 100 mg/kg/day in divided doses; serum level monitoring recommended.
- adult · IV: 12.5–25 mg/kg Q6H · Max 100 mg/kg/day in divided doses; serum level monitoring recommended.
Typhoid fever
Use only if other antibiotics are unsuitable; 500 mg every 6 hours for adults is also used.
- adult · PO: 12.5 mg/kg Q6H · Use only if other antibiotics are unsuitable; 500 mg every 6 hours for adults is also used.
Bacterial conjunctivitis
0.5% ophthalmic solution; discard after 7 days.
- adult · TOP: 1–2 drops Q2-4H · 0.5% ophthalmic solution; discard after 7 days.
Neonatal sepsis (life-threatening)
Risk of gray baby syndrome; monitor serum levels and avoid in preterm infants if possible.
- neonatal · IV: 25 mg/kg Q12H · Risk of gray baby syndrome; monitor serum levels and avoid in preterm infants if possible.
Contraindications & precautions
- Hypersensitivity to chloramphenicol or any ingredient of the preparation
- Neonates (particularly preterm) · Risk of grey baby syndrome; use only if no alternative and monitor plasma concentrations.
- Pregnancy · Crosses placenta; reserve for severe infections with no alternative.
- History of blood dyscrasias · Increased risk of bone marrow toxicity.
- Hepatic impairment · Reduce dose or avoid if severe; monitor liver function.
- Monitor full blood count regularly during treatment, especially with prolonged therapy.
- Do not use for trivial infections or for prophylaxis where safer alternatives exist.
- Reduce dose in hepatic impairment and monitor liver function tests.
- Avoid concurrent use with other drugs that may cause bone marrow suppression, such as cytotoxics or radiotherapy.
- Use with caution in neonates and preterm infants; if essential, monitor plasma chloramphenicol concentrations closely.
- Use with caution in pregnancy and breastfeeding, weighing risks against benefit.
Adverse effects
- Aplastic anaemiaserious
- Reversible bone marrow suppressionserious
- Grey baby syndrome (in neonates)serious
- Nausea and vomiting
- Diarrhoea
- Rash
- Peripheral neuropathyserious
- Optic neuritisserious
Renal & hepatic adjustment
- Hepatic impairment (mild): No dose reduction usually required; monitor plasma levels if available.
- Hepatic impairment (moderate): Consider reducing the dose and monitoring plasma concentrations.
- Hepatic impairment (severe): Avoid use; select an alternative antibiotic. (avoid)
Monitoring, pregnancy & toxicity
- Full blood count (incl. platelets and reticulocytes) · Baseline, then every 2-3 days during therapy
- Serum chloramphenicol concentration · Where available, especially in hepatic impairment and neonates
- Liver function tests · In hepatic impairment, baseline and periodic
- Pregnancy: Avoid use during pregnancy unless clearly indicated; risk of bone marrow suppression and grey baby syndrome in the newborn.
- Toxicity: Bone marrow suppression (anaemia, leucopenia, thrombocytopenia) · Monitor blood count; stop drug if significant; supportive care.
- Toxicity: Aplastic anaemia (rare, potentially fatal) · Stop drug immediately; urgent haematology review; avoid re-exposure.
- Toxicity: Grey baby syndrome (neonates, premature infants; causes ashen grey colour, abdominal distension, hypotension, acidosis) · Stop drug; supportive measures, including exchange transfusion in severe cases.
- Toxicity: Peripheral neuropathy or optic neuritis (rare) · Stop drug; neurological assessment; symptomatic treatment.
Clinical notes
Chloramphenicol is reserved for serious infections when safer alternatives are ineffective or contraindicated, such as meningitis, rickettsial infections, typhoid fever, and brain abscess. The most important adverse effects are dose-related bone marrow suppression and rare, idiosyncratic aplastic anaemia. Gray baby syndrome can occur in neonates, especially the premature, due to impaired glucuronidation. Serial blood counts are advised during treatment. It is generally avoided in pregnancy and neonates. Availability and indications vary by region and formulary.
Log in to read the full chloramphenicol monograph
A free account unlocks the complete drug reference, the interaction checker, prescription practice and every other learning tool.
BNF; local formulary