Chloramphenicol is an antibiotic Overview of Antibacterial Drugs Antibacterial drugs are derived from bacteria or molds or are synthesized de novo. Technically, “antibiotic” refers only to antimicrobials derived from bacteria or molds but is often (including... read more that is primarily bacteriostatic. It binds to the 50S subunit of the ribosome, thereby inhibiting bacterial protein synthesis.
Pharmacokinetics
Chloramphenicol is well absorbed orally. Parenteral therapy should be IV.
Chloramphenicol is distributed widely in body fluids, including cerebrospinal fluid, and is excreted in urine. Because of hepatic metabolism, active chloramphenicol does not accumulate when renal insufficiency is present.
Indications for Chloramphenicol
Chloramphenicol has a wide spectrum of activity against
Gram-positive and gram-negative cocci and bacilli (including anaerobes Overview of Anaerobic Bacteria Bacteria can be classified by their need and tolerance for oxygen: Facultative: Grow aerobically or anaerobically in the presence or absence of oxygen Microaerophilic: Require a low oxygen concentration... read more )
Rickettsia Overview of Rickettsial and Related Infections Rickettsial diseases (rickettsioses) and related diseases (anaplasmosis, ehrlichiosis, Q fever, scrub typhus) are caused by a group of gram-negative, obligately intracellular coccobacilli. All... read more
, Mycoplasma Mycoplasmas Mycoplasmas are ubiquitous bacteria that differ from other prokaryotes in that they lack a cell wall. Mycoplasma pneumoniae is a common cause of pneumonia, particularly community-acquired... read more , Chlamydia Mycoplasmas Mycoplasmas are ubiquitous bacteria that differ from other prokaryotes in that they lack a cell wall. Mycoplasma pneumoniae is a common cause of pneumonia, particularly community-acquired... read more , and Chlamydophila species
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 Treatment
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.
Contraindications to Chloramphenicol
Chloramphenicol is contraindicated if another drug can be used instead.
Use During Pregnancy and Breastfeeding
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
Adverse effects of chloramphenicol include
Bone marrow depression (most serious)
Nausea, vomiting, and diarrhea
Gray baby syndrome (in neonates)
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 Aplastic Anemia Aplastic anemia is a disorder of the hematopoietic stem cell that results in a loss of blood cell precursors, hypoplasia or aplasia of bone marrow, and cytopenias in two or more cell lines ... read more
: 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.
