Further observations on chloramphenicol toxicosis in cats

After a base-line period (14 days), five cats were orally given 50 mg of chloramphenicol every 12 hours for 21 days. Clinical signs of toxicosis were CNS depression, reduced intake of food and water, and weight loss. Changes in peripheral blood included lower platelet counts after treatment for 1 week and fewer neutrophils after treatment for 3 weeks; one cat developed lymphocytopenia after 1 week and neutropenia after 2 weeks. Changes in bone marrow at the end of treatment comprised vacuolation of early myeloid cells and lymphocytes, and reduced myeloid maturation ratio, and some cats also had reduced marrow cellularity, or increased myeloid:erythroid ratio, or both of these.