Int. J. Environ. Res. Public Health 2010, 7 2043 progressing to blastocyst stage of development compared with their counterparts in the continuous regimen of embryo culture in the presence of HU. Although HU is a potential antineoplatic agent, inhibitor of viral development, a beneficial drug for the alleviation of clinical manifestations of SCD and a well tolerated drug, it is highly toxic to preimplantation embryos. The ability of some embryos exposed to HU to develop to blastocyst stage indicates resilience to xenobiotics by some embryos. However, subtle damage may still occur in the surviving embryos and may be expressed post partum if exposure is high enough and continuous. Patients on HU that are considering a family should consult with their physicians before they attempt pregnancy. Acknowledgements References This work was supported in part by PHS grants No. G12RRO3032 (A.E.A), 1U54HD044315, RO1 HD020419-19S1 (A.E.A). 1. 2. 3. 4. 5. 6. 7. 8. 9. Yarbro, J.W. Mechanism of action of hydroxyurea. Semin. Oncol. 1992, 19, 1-10. Caramazza, D.; Caracciolo, C.; Barone, R.; Malato, A.; Saccullo, G.; Cigna, V.; Berretta, S.; Schinocca, L.; Quintini, G.; Abbadessa, V.; Di Raimondo, F.; Siragusa, S. Correlation between leukocytosis and thrombosis in Philadelphia-negative chronic myeloprolipherative neoplasm. Ann. Hematol. 2009, 88, 967-971. Cortelazzo, S.; Finazzi, G.; Ruggeri, M.; Vestri, O.; Galli, M.; Rodeghiero, F.; Barbui, T. Hydroxyurea for patients with essential thrombocythemia and a high risk of thrombosis. N. Engl. J. Med. 1995, 332, 1132-1136. Silver, R.T.; Woolf, S.H.; Hehlmann, R.; Appelbaum, F.R.; Anderson, J.; Bennett, C.; Goldman, J.M.; Guilhot, F.; Kantarjian, H.M.; Lichtin, A.E.; Talpaz, M.; Tura, S. An evidence-based analysis of the effect of busulfan,hydroxyurea, interferon, and allogeneic bone marrow transplantation in treating the chronic phase of chronic myeloid leukemia: developed for the American Society of Hematology. Blood 1999, 94, 1517-1536. Steinberg, M.H. Management of sickle cell disease. N. Engl. J. Med. 1999, 340, 1021-1030. Gao, W.; Cara, A.; Gallo, R.; Lori, F. Low levels of deoxynucleotides in peripheral blood lymphocytes: a strategy to inhibit HIV type 1 replication. Proc. Natl. Acad. Sci. USA 1993, 90, 8925-8928. Bakshi, R.P.; Hamzeh, F.; Frank, I.; Eron, J.J., Jr; Bosch, R.J.; Rosenkranz, S.L.; Cramer, Y.S.; Ussery, M.; Flexner, C. Effect of hydroxyurea and dideoxyinosine on intracellular 3’-deoxyadenosine-5’-triphosphate concentrations in HIV-infected patients. AIDS Res. Hum. Retroviruses. 2007, 11, 1360-1365. Chahoud, I.; Paumgartten, F.J. Dose-response relationships of rat fetal skeleton variations: Relevance for risk assessment. Environ. Res. 2009, 109, 922-929. Woo, G.H.; Katayama, K.; Bak, E.J.; Ueno, M.; Yamauchi, H.; Uetsuka, K.; Nakayama, H.; Doi, K. Effects of prenatal hydroxyurea-treatment on mouse offspring. Exp. Toxicol. Pathol. 2004, 56, 1-7.