• Metabolism: Hepatic, with 90% conjugated to inactive glucuronide. Half Life: Half-life in adults with normal hepatic and renal function is 1.5 - 3.5 hours. In patients with impaired renal function half-life is 3 - 4 hours. In patients with severely impaired hepatic function half-life is 4.6 - 11.6 hours. Half-life in children 1 month to 16 years old is 3 - 6.5 hours, while half-life in infants 1 to 2 days old is 24 hours or longer and is highly variable, especially in low birth-weight infants.
• Uses/Sources: Used in treatment of cholera, as it destroys the vibrios and decreases the diarrhea. It is effective against tetracycline-resistant vibrios. It is also used in eye drops or ointment to treat bacterial conjunctivitis.
• Health Effects: The most serious adverse effect associated with chloramphenicol treatment is bone marrow toxicity, which may occur in two distinct forms: 1) bone marrow suppression, which is a direct toxic effect of the drug and is usually reversible, and 2) aplastic anemia, which is idiosyncratic (rare, unpredictable) and generally fatal. Other less serious reactions from chloramphenicol use include fever, rashes, headache, and confusion. Use of intravenous chloramphenicol has also been associated with gray baby syndrome, a phenomenon resulting from newborn infants' inability to metabolize chloramphenicol in the liver via UDP-glucuronyl transferase. Gray baby syndrome is characterized by vomiting, ashen gray color of the skin, limp body tone, hypotension and cyanosis.
• Symptoms: Toxic reactions including fatalities have occurred in the premature and newborn; the signs and symptoms associated with these reactions have been referred to as the gray syndrome. Symptoms include (in order of appearance) abdominal distension with or without emesis, progressive pallid cyanosis, vasomotor collapse frequently accompanied by irregular respiration, and death within a few hours of onset of these symptoms.
• Treatment: Drug therapy is discontinued immediately; exchange transfusion may be required to remove the drug. Sometimes, phenobarbital (UGT induction) is used.
• Route of Exposure: Rapidly and completely absorbed from gastrointestinal tract following oral administration (bioavailability 80%). Well absorbed following intramuscular administration (bioavailability 70%). Intraocular and some systemic absorption also occurs after topical application to the eye.

• Carcinogenicity: 2A, probably carcinogenic to humans. (L135)
• Toxicity: Oral, mouse: LD50 = 1500 mg/kg Oral, rat: LD50 = 2500 mg/kg.

Chloramphenicol targets the large 39S subunit of the mitochondrial ribosome thereby deactivation mitochondrial protein synthesis. As a result chloramphenicol is cytotoxic to the most metabolically active cells or tissues including the heart, liver, thymus and bone-marrow. (A7823). The likely target of chloramphenicol is the 16S rRNA molecule in the mitochondrial ribosome, which is analogous to the 23S rRNA in bacterial ribosomes.