VITAMIN K

Sathish kumar.RAltheanz 09

It is a fat soluble dietary principle required for the synthesis of clotting factors.

Chemistry◦ Vitamin k has a naphthoquinone ring and a side

chain(R).

Based on the alkyl (R)group vitamin k may be classified as

K1 – (R-phytyl)phytonadione phylloquinone

K2 – (R-prenyl)menaquinone

K3 – no side chain menadioneacetamenaphthone

DIETARY SOURCE• Green leafy vegetables such as cabbage,

spinach and liver, cheese,etc…

RDA It is uncertain because colonic bacteria

itself produces a variable amount of menaquinone ( vit k2)

However the total requirement for an adult has been estimated to be 50-100 µg/day

UTILIZATION Water soluble vitamin absorb directly

into portal blood. Fat soluble vitamins

Absorbed from intestine via lymph( requires bile salts for absorption)

Temporarily stored in liver

Metabolized by side chain cleavage, glucuronide conjugation

Metabolites are excreted in bile & urine

Vitamin K has a main role in coagulation It acts as a cofactor in late stage of

synthesis of coagulation proteins ( prothrombin, factors

vii,ix,x) which are synthesized by liver as inactive zymogens.

PHYSIOLOGICAL ROLE

Vit K dependent carboxylase

Warfarin Dicoumarol

Gamma carboxy glutamic acid

Get bound to phospholipid surfaces

Participate in coagulation cascade

Vitamin K to a certain extent aids in bone formation through

gamma carboxylation of osteocalcin

Binds tightly to hydroxy apatite crystals of bone

Only use is in prophylaxis and treatment of bleeding due to deficiency of clotting factorsin following situations

DIETARY DEFICIENCY Rare but when it occurs 5–10 mg/day oral

or parenteral vitamin K is administered PROLONGED ANTIMICROBIAL THERAPHY OBSTRUCTIVE JAUNDICE, MALABSORPTION

SYNDROMES vit K 10mg i.m/day or orally along with

bile salts.

USES

LIVER DISEASES (CIRRHOSIS, VIRAL HEPATITIS) Vit K may be of some use here

NEW BORNS• due to lower capacity to synthesise clotting

factors• Vit K 1mg i.m soon after birth • Administered 5- 10 mg i.m to mother 4-12 hrs

before delivery

PROLONGED HIGH DOSE SALICYLATE THERAPY CAUSING HYPOPROTHROMBINEMIA

OVER DOSE OF ORAL ANTICOAGULANTS causing hypoprothrombinemia, bleeding Vitamin K1(phytonadione) is given. It is the

drug of choice because it acts rapidly

If severe bleeding occurs • 10 mg i.m followed by 5mg 4 hourly• Bleeding stops in 6-12 hrs• But the normal levels of coagulation factors

are restored only after 24 hrs

• Hemorrhagic disease of newborn• Bruising tendency• Echymotic patients• Mucous membrane haemorrhage• Post – traumatic bleeding• Internal bleeding(GIT, Nose)• Prolonged clotting,prothrombin time• haematuria

DEFICIENCY MANIFESTATIONS

Rapid i.v injection of emulsified vit K causes Flushing Breathlessness Chest constriction Fall in B.P

manifestations of toxicity are Hemolysis Hyperbilirubinemia-by competitive

inhibition of glucuronidation Kenicterus

ADVERSE EFFECTS

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