抗生剤投与が血清ビタミンＫ濃度に及ぼす影響

Abstract

Vitamin K deficiency has occurred in patients receiving broad-spectrum antibiotics. The mechanism of hypoprothrombinemia in patients treated with antibiotics is still unknown, although it is suggested to result from impared synthesis of vitamin K by suppression of intestinal bacteria or interference of vitamin K utilization in the liver. We studied the serum vitamin K concentration in patients receiving broad-spectrum antibiotics for 7 days or more, in order to clarify the mechanism of antibiotics induced vitamin K deficiency. The coagulation abnormalities compatible with vitamin K deficiency were seen in 7 patients in whom predisposing factors for vitamin K deficiency were male, poor dietary intake and therapy of antibiotics with N-methyl-tetrazol thiol. In these patients, serum vitamin K1 and vitamin K2 (menaquinone-7) levels was extremly lower when compared to normal adult levels. On the other hand, vitamin K1 levels in 5 of 6 patients with normal coagulation status moderately decreased to the levels under minus 1 standard deviation of normal adults, and serum vitamin K2 in 3 patients with normal coagulation status and very poor dietary intake was not detected.These results may suggest that vitamin K deficiency in patients receiving antibiotics is induced by poor oral intake, altered absorption of vitamin K in the intestine and/or impaired synthesis of vitamin K by suppression of intestinal bacteria.