Book of Medical Disorders in Pregnancy - Tintash

also be used for arranging the next dose
of heparin. Over dosage of heparin can
be easily reversed by giving protamine
sup late 1 mg per 1000 units of heparin.
Heparin:
Sulph ated carbohydrate: Different size
bovine lungs, Administration parenteral
do not inject IM - only IV or deep S.C.
Half-life 1 - 5 hrs - monitor aPTT.
Adverse effect: hemorrhage Anti-dote:
protamine sulphate.
Oral anticoagulants:
Examples: Coumarins - warfarin,
dicumarol, structurally related to vitamin
K, Inhibits production of active clotting
factors, Clearance is slow - 36 hrs,
Delayed onset 8 - 12 hrs overdose -
reversed by vitamin K infusion and can
cross placenta - do not use during late
pregnancies.
Mechanism of action:
Normally, vitamin K is converted to
vitamin K epoxide in the liver. This
epoxide is then reduced by the enzyme
epoxide reductase. The reduced form of
vitamin K epoxide is necessary for the
synthesis of many coagulation factors (II,
VII, IX and X, as well as protein C and
protein S). Warfarin inhibits the enzyme
epoxide reductase the liver, thereby
inhibiting coagulation.
Warfarin side effect:
Severe Side effects: Severe bleeding
from the rectum or black stool Skin
conditions such as hives, a rash or
itching. Swelling of the face, throat,
mouth, legs, feet or hands, bruising that
comes about without an injury you
140
remember, Chest pain or pressure
Nausea or vomiting, fever or flulike
symptoms. Joint or muscle aches
diarrhea, difficulty moving Numbness of
tingling in any part of your body and
Painful erection lasting four hours or
longer.
Other less serious warfarin side
effects:
Gas, feeling cold, fatigue, pale skin
changes in the way foods taste and Hair
loss.
Drug interaction with warfarin:
Category Mechanism Representati
ve Drugs
Drugs that
Increase
Warfarin Activity
Drugs that
promote
bleeding
Warfarin activity
Drugs that
decrease
Decrease binding to
Albumin inhibit
degradation
decrease synthesis of
clotting Factors
Inhibition of platelets
Factors
Inhibition of clotting
Promote clotting
factor
Reduced absorption
Synthesis
Aspirin,
Sulfonamides
Cimetidine,
Disulfiram
Antibiotics
(oral)
Aspirin
heparin
antimetabolit
es
Vitamin K
Colestipol
Cholestyrami
ne
Naphthoquinone - This group of drugs
include dicoumarol, and phenindione.
These drugs are chemically similar to
Vitamin K. They act by replacing
Vitamin K at the site of prothrombin
formation. They also prevent the hepatic
synthesis of factor VII, IX and X. The
anticoagulant effect of heparin is
immediate and maximal after
intravenous injection, but decreases
rapidly over the course of few hours.
The effect of oral anticoagulants on the
other hand, is negligible for the first 24