Vitamin teratogenic

Arnhold, T, Ehnazar, M.M.A., and Nau, H., Prevention of vitamin A teratogenesis by phytol or phytanic acid results from reduced metabolism of retinol to the teratogenic metabolite, all frara-retinoic acid, Toxicol. Sci., 66, 274, 2002. 

Nonpharmacologic therapy such as dietary, physical, and behavioral approaches should be considered first. Pyridoxine (vitamin B6) 10 to 25 mg three to four times daily alone or in combination with an antihistamine such as doxylamine is often used for NVP.9,11,12 This combination was previously marketed as Bendectin or Debendox but was withdrawn due to concerns over possible teratogenic effects, although the literature did not support this claim.11,12 Pyridoxine is well tolerated, but doxylamine and other antihistamines commonly cause drowsiness. For more severe NVP, promethazine, meto-clopramide, and trimethobenzamide may be effective and have not been associated with teratogenic effects.9... 

Which of the following vitamins in large doses is teratogenic ... 

High concentrations of vitamin A in pregnancy tend to be teratogenic leading to birth defects. Hence vitamin A is contraindicated in pregnancy. 

Tanaka H, Inomata K, Arima M Teratogenic effects of triethylene tetramine dihydrochloride on the mouse brain. J Nutr Sci Vitamin 39 177-188, 1993... 

The activity of vitamin A is related to vision process, tissue differentiation, growth, reproduction, and the immune system. A deficiency of this micronutrient mainly leads to visual problems, impaired immune function, and growth retardation in children. Hypervitaminosis could lead to hepatotoxicity, affect bone metabolism, disrupt lipid metabolism, and teratogenicity [417]. The isomerization of P-carotene, due to technological processes in foods, leads to a reduction of the vitamin A activity it is therefore important to analyze it. 

Deficiency of vitamins, such as folic acid, is highly teratogenic, as essential synthetic metabolic pathways are blocked or reduced. This may be caused by the administration of specific vitamin analogues or antagonists as well as by a failure in supply. 

Changes in membrane permeability might be expected to lead to osmolar imbalance and fetal abnormality. This is hypothetical, as there are no real examples of such a mechanism, although high doses of vitamin A are teratogenic and may cause ultras true tural membrane damage. 

Much recent interest has been aroused by the fact that retinoid compounds, including both retinol and retinoic acid, reduce the incidence of experimentally induced cancer. In addition, 13-czs-retinoic acid taken orally is remarkably effective in treatment of severe cystic acne. s However, both vitamin A and retinoic acid in large doses are teratogenic, i.e., they cause fetal abnormalities. The use of 13-cis-retinoic acid during early phases of pregnancy led to a high incidence of major malformations in infants born.1 11 1... 

Rothman KJ, Moore LL, Singer MR, Nguyen US, Mannino S, Milunsky A. Teratogenicity of high vitamin A intake. N Engl J Med 1995 333(21) 1369-73. 

M4. Moestrup, S. K., Kozyraki, R., Kristiansen, M., Kaysen, J. H., Rasmussen, H. H., Brault, D., Pontillon, F., Goda, F. O., Christensen, E. I., Hammond, T. G., and Verroust, P. J., The intrinsic factor-vitamin B12 receptor and target of teratogenic antibodies is a megalin-binding peripheral membrane protein with homology to developmental proteins. J. Biol. Chem. 273, 5235—5242 (1998). 

The biochemical aspects of teratology are not particularly well understood. Several kinds of biochemical mechanisms are probably involved. One such mechanism is interference with DNA synthesis, which alters the function of nucleic acids in cell replications, resulting in effects that are expressed as birth defects. Exposure to teratogenic xenobiotic substances may result in either an absence or excess of chromosomes. Enzyme inhibition (see Section 7.6) by xenobiotics can result in birth defects. Xenobiotics that deprive the fetus of essential substrates (for example, vitamins), that interfere with energy supply, or that alter the permeability of the placental membrane may all cause birth defects. 

In 1988, the U.S. Food and Drag Administration estimated that Accutane, used as an antiacne medication, may have been reponsible for approximately 1000 birth defects in children bom to women taking the drug during the period of 1982 to 1986. The chemical name for Accutane is isoretinoin, and it is chemically related to retinoic acid, vitamin A, which likewise is teratogenic at excessive levels. Exposure of the fetus to Accutane over a period of only several days can result in birth defects such as severe facial malformations, heart defects, thymus defects, and mental retardation.13... 

Vitamin A (in excessive doses) produces toxicity such as nausea, vomiting, erythema, dermatitis, hair loss, bone and joint pains, loss of appetite, bleeding, and chronic liver diseases. Excess vitamin A is teratogenic in animals and humans daily intake should not exceed 20,000 IU. 

During the 1980s, two drugs used to treat different types of skin diseases were found to be teratogenic. The drugs, generic names are isotretoin and etretinate, respectively, and they are synthetic retinoids (i.e., derivatives of vitamin A). Isotretoin (Accutane) was prescribed for the treatment of acne while etretinate was prescribed for psoriasis. 

Because of the potential teratogenic effects of high-dose vitamin A, caution must be taken in the treatment of severe vitamin A deficiency among pregnant women as well as women of reproductive age. Women of reproductive age should be treated with 200,000 IU only when they display active corneal xerophthalmia. For... 

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