Counseling Parameters for Warfarin

Warfarin is an anticoagulant (blood thinner). It reduces the formation of blood clots by blocking the formation of certain clotting factors. Counseling of drugs is one of the important responsibility of pharmacist. This article covers some useful parameters that must be communicated to the patients before dispensing the drugs to them.


Therapeutic Class:
Anticoagulant

Counseling for Indications:
Pharmacist should discuss with patient that why he has been prescribed and what possible benefits he will get after taking warfarin. Some recommended clinical uses of warfarin are mentioned below.

• Prophylaxis and treatment of venous thrombosis and its extension;
• Prophylaxis and treatment of atrial fibrillation with embolization;
• Prophylaxis and treatment of pulmonary embolism;
• Adjunct in prophylaxis of systemic embolism after MI.

Unlabeled use(s):

• Prevention of recurrent transient ischemic attacks and reduction of risk of recurrent MI
• adjunctive treatment of small cell carcinoma of lung.

Counseling for Dose:
Right drug at right dose is necessary in order to get optimized pharmacotherapy. If dose is less or more it will not be able to produce desired therapeutic effects because the lesser dose will cause therapeutic failure and higher dose will cause toxic effects. It is the duty of the pharmacist to verify the dose against indications.

• Initial: 2 to 5 mg orally or intravenously once a day for 1 to 2 days, then adjust dose according to results of the International Normalized Ratio (INR) or prothrombin time (PT).
• Maintenance: the usual maintenance dose ranges from 2 to 10 mg orally or intravenously once a day.
• Counsel the patient that If you have missed the dose, take the missed dose as soon as you remember,  Do not take two doses at the same time to make up a missed dose.
• Overdose can cause excessive bleeding.

Counseling for Administration:
Warfarin is available is tablet and parental dosage forms. Following points should be counseled by

pharmacist to the patients while dispensing warfarin.

For Oral Route:
Warfarin is usually taken once in a day. Instruct the patients that;

• Take medication at the same time each day with or without food
• Adhere strictly to the prescribed dosage and schedule of warafrin

For IV Route:

• Counsel the patient that intravenous (IV) route for the administration of warfarin is recommended when oral route is unable to get desired benefits. Remember it is not prescribed for intramuscular administration.
• Monitor the value of INR and PT in order to determine effectiveness of warfarin

Counseling for Side Effects:
The major side effect of wargarin is hemorrhage. So use of this drug should be done with great caution in patients who are already at higher risk of bleeding. Get emergency medical help if you have any of these signs of an allergic reaction to warfarin: hives; difficulty breathing; swelling of your face, lips, tongue, or throat.
Other common side effects of warfarin include alopecia, diarrhoea, unexplained drop in haematocrit, ‘purple toes’, skin necrosis, jaundice, hepatic dysfunction; also nausea, vomiting, and pancreatitis
Stop using warfarin and call your doctor at once if you have any of the serious side effect mentioned above.

Counseling for Pregnancy:
Warfarin has been assigned to pregnancy category X by the FDA. Problems associated with perinatal administration of warfarin have included central nervous system defects, spontaneous abortion, stillbirth, prematurity, hemorrhage, and ocular defects when given anytime during pregnancy, and a fetal warfarin syndrome when given during the first trimester. It use is very dangerous during the first and third trimester. So counsel the patient that  avoid intake of warfarin as it is contraindicated during pregnancy.

Counseling for Drug Interaction:
Self medication is very common in Pakistan and patients take NSAIDs like aspirin and various other drugs without consulting with physician. It is the responsibility of pharmacist to tell patients that do not take aspirin while being treated with warfarin unless advised by your doctor because aspirin interferes with platelet aggregation and increases the risk of bleeding. Thus is not recommended to patients receiving oral anticoagulants (eg warfarin) unless low-dose aspirin is intentionally prescribed. Other oral NSAIDs should also be avoided in patients receiving oral anticoagulants unless otherwise directed by the prescriber. Drugs  which decrease the effect of warfarin are:
Aminoglutethimide, azathioprine, barbiturates, carbamazepine, cholestyramine, ethchlorvynol, glutethimide, griseofulvin, mercaptopurine, rifabutin, rifampin, trazodone, and vitamin K.

• Drugs which increase the effect of warfarin are:

Androgens, amiodarone, cefamandole, cefazolin, cefoperazone, cefotetan, cefoxitin, ceftriaxone, chloramphenicol, cimetidine, clofibrate, dextrothyroxine, disulfiram, erythromycin, fluconazole, glucagon, methimazole, metronidazole, miconazole, moxalactam, nalidixic acid, nonsteroidal anti-inflammatory agents, phenylbutazone, propylthiouracil, quinidine, quinine, salicylates, sulfinpyrazone, sulfonamides, thyroid hormones, tricyclic antidepressants, and vitamin E.

Counseling for Food-drug Interactions:
Warfarin is a blood thinning medication and its therapeutic effectiveness is dependent upon the presence of vitamin K in your body.  Normally the standard permitted amount of vitamin K in adult men and women is 20 micrograms (mcg) and 90 mcg respectively. If you are taking a food rich in vitamin K then effectiveness of warfarin will be altered. So counsel the patient that does not take food rich in vitamin K. Here is a list of foods that contain higher amount of vitamin K.

• Kale
• Spinach
• Brussels sprouts
• Parsley
• Collard greens
• Mustard greens
• Chard
• Green tea

Counsel the patient about the use of some drink and juices like alcohol, cranberry juice that could increase the risk of bleeding. So use of such drinks/juices should be as limited as possible.

Counseling for Contraindications:
Counsel the patient that do not use warfarin if you are suffering from peptic ulcer, severe hypertension; renal impairment (avoid if creatinine clearance less than 10 ml/minute) or pregnancy because warfarin is contraindicated in above mentioned conditions.

Counseling for Storage:
Advise the patient that store the medicine in a closed container, at room temperature, away from heat, moisture, and direct light.

• Keep from freezing.
• Keep out of the reach of children.
• Do not keep outdated medicine or medicine  no longer needed.

Brand Name:

• Warfarin
• FERICARD
• COAGURIN
• ANTICOAG
• FERICARD

References:

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