ビタミンK_1(1mg)筋注後の新生児血漿中ビタミンK_1エポキシド濃度

抄録

Vitamin K(K) is prophylactically administered to neonates to prevent hemorrhagic diseases of the newborn. Some recent reports suggest that the risk of childhood cancer significantly increased with the intramuscular injection of K. K is cyclically metabolized to K-epoxide in the liver microsomes, and K-epoxide reductase catalyzes the conversion of K-epoxide to K again. It is inferred that the epoxide group is likely to injure the DNA and becomes carcinogenic by releasing superoxide. The object of this study is to estimate the K_1-epoxide appearance in neonatal plasma after intramuscular injection of K_1 (1 mg) and compare with the control group. In the control group (n=9) between 2.8 and 93.1 hours of age, the mean concentration of K_1 was 2.7 ng/ml (range 0.6〜5.8) and K_1-epoxide was not detectable (<0.5 ng/ml) in any sample. In the administered group (n=17) between 5.7 and 93.8 hours of age, the mean concentration of K_1 was 246.2 ng/ml (range 6.4〜717.9) and significantly higher (p<0.005) than the control, and the mean concentration of K_1-epoxide was 3.5 ng/ml (range n.d.〜8.0). In the control group, short transit and very low concentration of K-epoxide have little toxic damage on infants. However, the long time exposure to higher levels of K-epoxide in plasma may increase the risk of childhood cancer by release of superoxide, although it is uncertain whether the maximum K_1-epoxide concentration (8.0 ng/ml) in this study may have adverse effects on his health or not.