Vitamin K

Vitamin K, or phytonadione, is a cofactor in the carboxylation of glutamate residues for coagulation factors II (prothrombin), VII, IX, and X and proteins C and S.
Consumption of green leafy vegetables, meats, and dairy products provides 50 percent of the body's vitamin K requirement. Stomach and intestinal flora synthesize the other 50 percent. Vitamin K deficiency impairs coagulation and leads to bleeding.
Bleeding may occur anywhere in the body and in some cases can be massive. In babies vitamin K deficiency is called hemorrhagic disease of the newborn. Areas of predilection include the umbilicus, skin, nose, mouth, intestines, and in the brain.vitamin K deficiencyin babies is caused by poor placental transfer of the vitamin from mother, inadequate dietary intake, and absent vitamin K synthesis by the gut. Premature infants are especially at risk for vitamin K deficiency. As prophylaxis, newborns are routinely given 1 mg of vitamin K intramuscularly at birth.
Several other factors may precipitate vitamin K deficiency. These include states of fat malabsorption
anorexia nervosa, and prolonged antibiotic therapy. Some drugs interfere with the physiologic role of vitamin K.
Newborns of mothers who take phenytoin are at increased risk for the development of bleeding disease.
The diagnosis can be confirmed by a prothrombin time measurement. phytonadione (vitamin K 1)injection is the treatment. Dosage is 5 to 10 mg in adults, 2 mg in young children, and 1 mg in newborns, who usually receive it routinely. Because coagulation factor synthesis requires several days, acute bleeding should be managed with fresh-frozen plasma.
Skin reactions occurring after vitamin K 1 injection occur rarely. These include an acute eczematous reaction and, more rarely, a late-onset localized sclerosis and atrophy resembling morphea.