Which statement correctly distinguishes the two forms of chloramphenicol-induced bone marrow injury?

• A Both the reversible suppression and aplastic anemia are dose-dependent
• B Reversible suppression is genetically determined, while aplastic anemia follows total dose
• C Aplastic anemia occurs only in neonates receiving high doses
• D Reversible marrow suppression is dose-related, whereas aplastic anemia is idiosyncratic and unrelated to dose ✓

Explanation

Chloramphenicol causes two distinct hematologic toxicities. Reversible bone marrow suppression reflects direct mitochondrial toxicity of the nitrobenzene moiety, is dose- and duration-related, and recovers on stopping the drug. Aplastic anemia is rare, idiosyncratic, typically appears weeks to months after exposure even to small or topical doses, is unrelated to serum concentration, and carries a high mortality. Gray baby syndrome is a separate neonatal toxicity caused by deficient glucuronidation, not marrow failure.

Reference: Goodman and Gilman's The Pharmacological Basis of Therapeutics, 14th ed.

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