Chloramphenicol is an antibiotic that is primarily bacteriostatic. It binds to the 50S subunit of the ribosome, thereby inhibiting bacterial protein synthesis.
Chloramphenicol has a wide spectrum of activity against
Gram-positive and gram-negative cocci and bacilli (including anaerobes)
Because of bone marrow toxicity, the availability of alternative antibiotics, and the emergence of resistance, chloramphenicol is no longer a drug of choice for any infection, except for
Serious infections due to a few multidrug-resistant bacteria that remain susceptible to this antibiotic
Plague meningitis or endophthalmitis because other plague drugs penetrate these spaces poorly
However, when chloramphenicol has been used to treat meningitis caused by relatively penicillin-resistant pneumococci, outcomes have been discouraging, probably because chloramphenicol has poor bactericidal activity against these strains.
Use of chloramphenicol during pregnancy results in fetal drug levels almost as high as maternal levels. Gray baby syndrome is a theoretical concern, particularly near term, but there is no clear evidence of fetal risk.
Chloramphenicol enters breast milk. Safety during breastfeeding has not been determined.
Adverse effects of chloramphenicol include
There are 2 types of bone marrow depression:
Reversible dose-related interference with iron metabolism: This effect is most likely with high doses or prolonged treatment or in patients with a severe liver disorder.
Irreversible idiosyncratic aplastic anemia: This anemia occurs in < 1/25,000 treated patients. It may not develop until after therapy is stopped. Chloramphenicol should not be used topically because small amounts may be absorbed and, rarely, cause aplastic anemia.
Hypersensitivity reactions are uncommon. Optic and peripheral neuritis may occur with prolonged use.
The neonatal gray baby syndrome, which involves hypothermia, cyanosis, flaccidity, and circulatory collapse, is often fatal. The cause is high blood levels, which occur because the immature liver cannot metabolize and excrete chloramphenicol. To avoid the syndrome, clinicians should not give infants ≤ 1 month of age > 25 mg/kg/day initially, and doses should be adjusted based on blood levels of the drug.