According to Kastens review published in the Mayo Clinic Proceedings, a serum concentration of more than 50 μg/mL is a warning sign, while Hammett-Stabler and John states that the common therapeutics peak level is 10-20 μg/mL and is expected to achieve after 0.5-1.5 hours of intravenous administration in their review of antimicrobial drugs. The common onset of signs and symptoms are 2 to 9 days after the initiation of the medication, which allows the serum concentration to build up to reach the toxic concentration above. Common signs and symptoms include loss of appetite, fussiness, vomiting, ashen gray color of the skin, hypotension (low blood pressure), cyanosis (blue discoloration of lips and skin), hypothermia, cardiovascular collapse, hypotonia (muscle stiffness), abdominal distension, irregular respiration, and increased blood lactate. Pathophysiology
Two pathophysiologic mechanisms are thought to play a role in the development of gray baby syndrome after exposure to chloramphenicol. This condition is due to a lack of glucuronidation reactions occurring in the baby (phase II hepatic metabolism), thus leading to an accumulation of toxic chloramphenicol metabolites:
Metabolism: The UDP-glucuronyl transferase enzyme system in infants, especially premature infants, is not fully developed and incapable of metabolizing the excessive drug load needed to excrete chloramphenicol. Elimination: Insufficient renal excretion of the unconjugated drug.Insufficient metabolism and excretion of chloramphenicol leads to increased blood concentrations of the drug, causing blockade of the electron transport of the liver, myocardium, and skeletal muscles. Since the electron transport is an essential part of cellular respiration, its blockade can result in cell damage.
According to the Oxford Review, chloramphenicol given to mothers during their pregnancy did not result in gray baby syndrome, but was caused by infants receiving supra-therapeutic doses of chloramphenicol after birth. The presentation of symptoms can depend on the level of exposure of the drug to the baby, given its dose-related nature. A broad diagnosis is usually needed for babies who present with cyanosis. To support the diagnosis, blood work should be done to determine the level of serum chloramphenicol, and to further evaluate chloramphenicol toxicity, a complete blood panel including levels of serum ketones, glucose (due to the risk of hypoglycemia), metabolic panel should be completed to help determine if an infant has the syndrome. Other tools used to help with diagnosis include CT scans, ultrasound, and electrocardiogram. Prevention
Since the syndrome is a side effect of chloramphenicol, the prevention is primarily related to the proper use of the medication. The WHO Model Formulary for Children 2010 recommends to reserve chloramphenicol for life-threatening infections. As well as using chloramphenicol only when necessary, it should also be used in short periods of time to also prevent the potential for toxicity. In particular, this medication should not be prescribed especially in neonates less than one week old due to the significant risk of toxicity. Preterm infants especially should not be administered chloramphenicol.