Chloramphenicol is a bacteriostatic antimicrobial originally derived from the bacterium Streptomyces venezuelae. It was the first antibiotic to be manufactured synthetically on a large scale, and alongside the tetracyclines, is considered the prototypical broad-spectrum antibiotic. Chloramphenicol is effective against a wide variety of Gram-positive and Gram-negative bacteria, including most anaerobic organisms. The most serious adverse effect associated with chloramphenicol use is bone marrow toxicity, which may occur in two distinct forms: bone marrow suppression, which is a direct toxic effect of the drug and is usually reversible, and aplastic anemia, which is idiosyncratic (rare, unpredictable, and unrelated to dose) and generally fatal. For research purposes only Structure of chloramphenicol chloramphenicol