Gray baby syndrome is caused by:

Chloramphenicol is a broad spectrum antibiotic Mechanism of action Chloramphenicol inhibits bacterial protein synthesis by interferring with 'transfer' of the elongating peptide chain to the newly attached aminoacyl-tRNA at the ribosome-mRNA complex. It specifically attaches to the 50S ribosome and thus may hinder the access of aminoacyl-tRNA to the acceptor site for amino acid incorporation (see Fig. 52.1). Probably by acting as a peptide analogue, it prevents formation of peptide bonds. At high doses, it can inhibit mammalian mitochondrial protein synthesis as well. Bone marrow cells are especially susceptible. Gray baby syndrome It occurred when high doses (-100 mg/kg) were given prophylactically to neonates, especially premature. The baby stopped feeding, vomited, became hypotonic and hypothermic, abdomen distended, respiration became irregular; an ashen gray cyanosis developed in many, followed by cardiovascular collapse and death. Blood lactic acid was raised. It occurs because of inability of the newborn to adequately metabolize and excrete chloramphenicol. At higher concentration, chloramphenicol blocks electron transpo in the liver, myocardium and skeletal muscle, resulting in the above symptoms. It should be avoided in neonates, and even if given, dose should be -25 mg/kg/day. Essentials of medical pharmacology K D Tripathi Sixth edition Pg no716 717 :