<s>[INST] context: Chloramphenicol was initially obtained from Streptomyces venezuelae in 1947. It was soon synthesized chemically and the commercial product now is all synthetic. Adverse effects 1 . Bone marrow depression Of all drugs, chloramphenicol is the most impoant cause of aplastic anaemia, agranulocytosis, thrombocytopenia or pancytopenia. Two forms are recognized: (a) Non-dose related idiosyncratic reaction: This is rare (1 in 40,000), unpredictable, but serious, often fatal, probably has a genetic basis and is more common after repeated courses. Aplastic anaemia is the most common manifestation. Apparently, a longer latent period of onset of marrow aplasia is associated with higher moality. Many victims, even if they survive, develop leukaemias later. (b) Dose and duration of therapy related myelosuppression: a direct toxic effect, predictable and probably due to inhibition of mitochondrial enzyme synthesis. This is often reversible without long-term sequelae. Liver and kidney disease predisposes to such toxicity. 2. Hypersensitivity reactions Rashes, fever, atrophic glossitis, angioedema are infrequent 3. Irritative effects Nausea, vomiting, diarrhoea, pain on injection. 4. Superinfections These are similar to tetracyclines, but less common. 5. 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 EDIYION PAGE NO:715,717 [/INST] question: Red cell aplasia can be caused by: | options: A: Aminoglycosides B: Chloramphenicol C: Penicillins D: Ciprofloxacin | answer: B </s>