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National Toxicology Program (NTP); Center for the Evaluation of Risks to Human Reproduction (CERHR); Availability of the Draft NTP Brief on Hydroxyurea; Request for Public Comments

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Information about this document as published in the Federal Register.

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National Institute of Environmental Health Sciences (NIEHS); National Institutes of Health (NIH).


Request for comments.


CERHR invites the submission of public comments on the draft NTP Brief for Hydroxyurea. The draft NTP Brief is available from the CERHR Web site (;​ see “Hydroxyurea” under “CERHR Reports & Monographs”) or in hardcopy from CERHR (see ADDRESSES below). Public comments will be considered during the peer review and finalization of the NTP Brief.


Written comments on the draft NTP Brief for Hydroxyurea should be received by May 1, 2008.


Public comments and any other correspondence should be addressed to Dr. Michael D. Shelby, CERHR Director, NIEHS, P.O. Box 12233, MD EC-32, Research Triangle Park, NC 27709 (mail), (919) 541-3455 (phone), (919) 316-4511 (fax), or (e-mail). Courier address: CERHR, 79 T.W. Alexander Drive, Building 4401, Room 103, Research Triangle Park, NC 27709.

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Hydroxyurea is used in the treatment of cancer, sickle cell disease, and thalassemia. It is the only treatment for sickle cell disease used in children, aside from blood transfusion and, in severe cases, bone marrow transplantation. Hydroxyurea may be used in the treatment of children and adults with sickle cell disease for an extended period of time or for repeated cycles of therapy. Treatment with hydroxyurea may be associated with cytotoxic and myelosuppressive effects and hydroxyurea is mutagenic. Hydroxyurea is FDA-approved for use in adults with sickle cell anemia to reduce the frequency of moderate to severe painful crises and the need for blood transfusions. CERHR selected hydroxyurea for evaluation because of: (1) Increasing use in the treatment of sickle cell disease in children and adults, (2) knowledge that it inhibits DNA synthesis and is cytotoxic, and (3) published evidence of reproductive and developmental toxicity in rodents. On January 24-26, 2007, CERHR convened an expert panel to conduct an evaluation of the potential reproductive and developmental toxicities of hydroxyurea. The expert panel report was released for public comment on February 26, 2007 (Federal Register Vol. 72, No. 37, pp. 8384-8385). Following this public comment period, CERHR staff prepared the draft NTP Brief for Hydroxyurea that provides in plain language:

  • Background information on the substance(s).
  • Findings of the expert panel.
  • Discussion of any relevant data available after the expert panel meeting.
  • NTP's conclusions on the potential for the substance to cause adverse reproductive and/or developmental effects in exposed humans.

Upon finalization, the NTP Brief for Hydroxyurea will be included in the CERHR Monograph for Hydroxyurea. The draft NTP Brief for Hydroxyurea and related background materials, including the hydroxyurea expert panel report and previously received public comments, are available on the CERHR Web site (;​ see “Hydroxyurea” under “CERHR Reports & Monographs”).

Request for Comments

The NTP invites written public comments on the draft NTP Brief for Hydroxyurea. Any comments received will be posted on the CERHR Web site and considered during the peer review and finalization of the NTP Brief for Hydroxyurea. Persons submitting written comments are asked to include their name and contact information (affiliation, mailing address, telephone and facsimile numbers, e-mail, and sponsoring organization, if any) and submit comments to Dr. Shelby (see ADDRESSES above) for receipt by May 1, 2008.

Background Information on CERHR

The NTP established CERHR in June 1998 (Federal Register Vol. 63, No. 239, p. 68782). CERHR is a publicly accessible resource for information about adverse reproductive and/or developmental health effects associated with exposure to environmental and/or occupational exposures.

CERHR invites the nomination of agents for review or scientists for its expert registry. Information about CERHR and the nomination process can be obtained from its homepage ( or by contacting Dr. Michael Shelby, CERHR Director (see ADDRESSES). CERHR selects chemicals for evaluation based upon several factors including production volume, potential for human exposure from use and occurrence in the environment, extent of public concern, and extent of data from reproductive and developmental toxicity studies. Expert panels conduct scientific evaluations of agents selected by CERHR in public forums. Following these evaluations, CERHR prepares the NTP-CERHR monograph on the agent evaluated. The monograph is transmitted to appropriate federal and state agencies and made available to the public.

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Dated: March 6, 2008.

Samuel H. Wilson,

Acting Director, National Institute of Environmental Health Sciences and National Toxicology Program.

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[FR Doc. E8-5242 Filed 3-14-08; 8:45 am]