Merck Manual

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Brian J. Werth

, PharmD, University of Washington School of Pharmacy

Reviewed/Revised May 2022 | Modified Sep 2022
Topic Resources


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

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

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. Use has been associated with gray baby syndrome in newborns but no teratogenic effects. It may be used in pregnancy to treat Rocky Mountain spotted fever if a 2nd-line agent is required, but caution is warranted in the 3rd trimester.

Chloramphenicol enters breast milk. It should not be used during breastfeeding; serious adverse reactions are possible, particularly in young or low weight infants.

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:

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.

Drugs Mentioned In This Article

Drug Name Select Trade
AK-Chlor, Chloromycetin, Chloroptic, Chloroptic S.O.P., Ocu-Chlor
NOTE: This is the Professional Version. CONSUMERS: View Consumer Version
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