Warfarin sodium: A coumarin group medicine of anticoagulants

2021-06-28 04:47 AM

Warfarin sodium injection solution is incompatible with adrenaline hydrochloride, amikacin sulfate, metaraminol tartrate, oxytocin, promazine hydrochloride, tetracycline hydrochloride, vancomycin hydrochloride.

International generic name: Warfarin.

Type of drug: Anticoagulant vitamin K antagonist.

Drug form and strength

Tablets: 1; 2; 2.5; 3; 4; 5; 6; 7.5; 10 mg warfarin sodium.

Warfarin sodium lyophilized powder, a vial of 5 mg, mixed with 2.7 ml of distilled water for injection to obtain a solution containing warfarin sodium 2 mg/ml.


Warfarin sodium is a coumarin anticoagulant, easily soluble in water, so it can be administered orally or injected.


Short-term treatment

Venous thromboembolism and acute pulmonary embolism, at the start of combination therapy with heparin. Prevention of thrombosis for patients who have to be immobilized for a long time after surgery.

Acute myocardial infarction: Prevention of venous thrombosis, surgery and supportive treatment of thrombolysis.

Long-term disease prevention

Patients with venous thrombosis and recurrent pulmonary embolism.

Cardiac disease at risk of embolism such as ventricular fibrillation, heart valve replacement, patients with transient ischemia, cerebral embolism.

Coronary heart disease (angina attack, myocardial infarction).


The patient does not cooperate well (does not comply with the doctor's instructions).

Malignant high blood pressure. Severe hemostasis disorder, severe liver disease, cirrhosis, steatorrhea.

Severe kidney failure. Tumors, ulcers of the gastrointestinal tract, or urogenital tract (bleed easily). Acute trauma or recent surgery to the central nervous system.

However, some patients can still be treated with medication if necessary but must be very careful.


Avoid intramuscular injection altogether, because of the risk of hematoma.

Several factors affect the effect of drugs: Diet, travel, environment.

Closely monitor people with liver disease, severe heart failure, atrial fibrillation, hyperthyroidism, fever.

The elderly are at increased risk of severe trauma (eg, femur fractures) and physiological changes in the subcutaneous tissues and joint spaces, which can result in uncontrolled diffuse bleeding.

The following factors can increase the effect of warfarin and need to reduce the dose, such as weight loss, elderly people, severe illness, kidney failure, vitamin K deficiency.

Factors that may necessitate an increase in maintenance dose: Weight gain, diarrhea, vomiting, high vitamin K intake, fat, and certain medications.

It is necessary to do the necessary tests when changing the drug form.

The effects of warfarin are reversed by vitamin K.

Pregnancy period

Warfarin and other anticoagulants of the cumin group cross the placental-fetal barrier and cause punctate osteochondrosis, bleeding, and stillbirth. Warfarin also increases the risk of bleeding in the mother during the second and third trimesters of pregnancy. Coumarin anticoagulants are not recommended during pregnancy. If anticoagulants are required during pregnancy, heparin should be used, as this drug does not cross the placenta.

Breastfeeding period

Warfarin is not excreted in breast milk, so it can be used by nursing mothers.

Side effects



Less common


Red rash.

Hair loss.




Dosage and Administration

Usage: Can be taken orally or intravenously. When the drug cannot be taken (vomiting after surgery), intravenous injection. Oral and intravenous doses are the same. Must be injected slowly and continuously over 1-2 minutes into a peripheral vein. Mix the drug in the vial with 2.7 ml of sterile water for injection. Before injecting, it is necessary to check that there is no cloudiness, no discoloration. After reconstitution, the drug is stable at room temperature for 4 hours. Discard unused medicine.

The medicine must be taken at the same time as prescribed on the days. If you forget to take the medicine once, you must take it immediately during the day. Do not take two doses of the drug (forgotten and next) at the same time.

Dosage: Dosage is determined for the individual, depending on the INR (international normalized ratio).

               Quick time of the patient

INR = ---------------------------------------------------------- = PTR( ISI)

                 Standard Quick Time

PT= Quick time.

PTR= ratio of the patient's Quick time divided by the standard Quick time.

The ISI is the international sensitivity index (of thromboplastin used compared with the international reference standard thromboplastin). Thus the ISI of the sample is by definition equal to 1.

Normal person's INR < 1.2. If INR > 5: Risk of major bleeding.

The usual initial dose is 5 - 10 mg/day for the first 2 days, then adjusted based on the results of the determination of the INR. Elderly people usually take a low initial dose. When rapid anticoagulation is required, use heparin for the first few days (intravenously or subcutaneously). Warfarin therapy can be either concurrently with heparin, or initiated after heparin.

Maintenance dose: Most patients are maintained with a dose of 2 - 10 mg/day.

The duration of treatment depends on the individual. Usually, anticoagulation therapy should be continued when the risk of embolism has passed.

Recommended INR range

INR = 2.0 - 3.0: Prevention of thrombosis - thromboembolism for high-risk medical or surgical patients; treatment of proximal venous thrombosis and pulmonary embolism, prevention of systemic embolism in patients with atrial fibrillation, valvular heart disease, bio-valvular implantation, or acute myocardial infarction.

INR = 3.0 - 4.5: Prevention of embolism in people with mechanical heart valves or in people with recurrent systemic embolism.

Periodic PT/INR monitoring: PT/INR must be determined prior to treatment. For the first 2 weeks, determine daily or 2 to 3 times per week. Thereafter, monthly in equilibrated patients or once every 1/2 months, if deemed necessary.


Be very careful when using oral anticoagulants, in combination with other drugs.

The effect of warfarin may be enhanced by: amiodarone, amitriptyline/nortriptyline, anabolic steroids, azapropazone, bezafibrate, cefamandole, chloral hydrate, chloramphenicol, cimetidine, clofibrate, co-cotrimoxazole, danazol, dextropropoxyphene, dextromolthyroxine, dipyridathyroxine, erythromycin, feprazone, glucagon, latamoxef, metronidazole, miconazole, neomycin, oxyphenbutazone, phenformin, phenylbutazone, phenyramidol, quinidine, salicylates, sulfonamides (eg, sulfaphenazol, sulfinpyrazone), tamoxifen, tolbutazone, tricyclic antidepressants, and triclofos, vitamin E, flu vaccine.

The effect of warfarin can be increased or decreased by: Phenytoin, ACTH, corticosteroids.

The effect of warfarin may be reduced when taken with alcohol (alcoholism), aminoglutethimide, barbiturates, carbamazepine, ethchlorvynol, glutethimide, griseofulvin, dichloralphenazone, methaqualone, primidone, rifampicin, an estrogen-containing oral contraceptive, spironolactone, sucralfate, vitamin K.


Store the tablets in a tightly closed bottle, protected from light, at a temperature of 15 - 300C.

Store the vial of powder for injection at a temperature of 15 - 300C, protected from light. Once the solution for injection has been mixed, it must be used within 4 hours, do not refrigerate, and dispose of unused solution.

When dissolving warfarin sodium in 0.9% sodium chloride or 5% glucose, the solution can be adsorbed by polyvinyl chloride. The adsorption will decrease when the pH of the solution is adjusted from 6.7 to 7.4.

The polyethylene or glass container does not adsorb the warfarin solution.


Do not add any other substances to the warfarin injection solution.

Warfarin sodium injection solution is incompatible with adrenaline hydrochloride, amikacin sulfate, metaraminol tartrate, oxytocin, promazine hydrochloride, tetracycline hydrochloride, vancomycin hydrochloride.

Overdose and treatment

If the bleeding or potential bleeding occurs, discontinue warfarin and, if necessary, infuse fresh serum or replace whole blood. Give vitamin K, orally or by injection 5-10 mg.


Table B poison.