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Chapter 25: Hematopoietic Agents

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Used prophylactically in pregnant women to prevent neural tube defects in the fetus:

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a. Riboflavin

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b. Pyridoxine

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c. Iron

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d. Vitamin B12

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e. Folic acid

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Answer is e. Folate deficiency has been implicated in the incidence of neural tube defects, including spina bifida, encephaloceles, and anencephaly. This is true even in the absence of folate-deficient anemia or alcoholism. The daily ingestion of a multivitamin preparation containing 400 to 500 μg of folic acid has become standard practice before and during pregnancy to reduce the incidence of neural tube defects and for as long as a woman is breast-feeding. In women with a history of a pregnancy complicated by a neural tube defect, an even larger dose of 4 mg/d has been recommended.

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Indicated for use in patients suffering from cyclic neutropenia to stimulate neutrophil production:

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a. Epoetin alfa

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b. Filgrastim

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c. Darbepoetin alfa

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d. Romiplostim

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e. Oprelvekin

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Answer is b. Filgrastim is a recombinant form of G-CSF that is administered by subcutaneous injection or slow intravenous infusion. Unlike natural G-CSF, it is not glycosylated and carries an extra N-terminal methionine. The principal action of filgrastim is the stimulation of CFU-G to increase neutrophil production (see Figure 25-1). It also enhances the phagocytic and cytotoxic functions of neutrophils. Its primary indication is in the treatment of severe neutropenia after autologous hematopoietic stem cell transplantation and high-dose cancer chemotherapy. Cyclic neutropenia is a congenital neutropenia that is characterized by a neutropenia that recurs every 14 to 35 days, with most patients exhibiting a cycle of 21 days. In patients with cyclic neutropenia, G-CSF therapy will increase the level of neutrophils and shorten the length of the cycle sufficiently to prevent recurrent bacterial infections.

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Figure 25-1. Sites of action of hematopoietic growth factors in the differentiation and maturation of marrow cell lines. A self-sustaining pool of marrow stem cells differentiates under the influence of specific hematopoietic growth factors to form a variety of hematopoietic and lymphopoietic cells. Stem cell factor (SCF), ligand (FL), interleukin-3 (IL-3), and granulocyte-macrophage colony-stimulating factor (GM-CSF), together with cell–cell interactions in the marrow, stimulate stem cells to form a series of burst-forming units (BFU) and colony-forming units (CFU): CFU-GEMM (granulocyte, erythrocyte, monocyte, and megakaryocyte), CFU-GM (granulocyte and macrophage), CFU-Meg (megakaryocyte), BFU-E (erythrocyte), and CFU-E (erythrocyte). After considerable proliferation, further differentiation is stimulated by synergistic interactions with growth factors for ...

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