Question

NR is an 89-year-old man (79.56kg, 73 in) with hypertension, hyperlipidemia, diabetes mellitus, vascular dementia, epilepsy and a history of prostate cancer. On April 29, 2016, he was admitted to the hospital with a diagnosis of acute kidney failure, dehydration, as well as pain and swelling in his left leg. On April 29, a venous sonogram was practiced in his left leg where deep thrombosis was identified in the iliofemoral vein. His medications include finasteride, ranitidine, metoprolol succinate, aspirin, terazosin, hydralazine, donepezil, memantine, insulin NPH and primidone. Enoxaparin 40mg every 24 hours and warfarin were started on April 30.

Warfarin Dosage:

04/30/2016       2.5mg

05/01/2016       2.5mg

05/02/2016       2.5mg

05/03/2016       2.5mg

05/04/2016       2.5mg

05/05/2016       2.5mg

05/06/2016       2.5mg

Reported INR:

04/29/2016       1.05

05/01/2016       1.20

05/03/2016       1.41

05/06/2016       1.59

What is the inR target range for this patient?

What factors would you consider when evaluating this patient? What drug-drug interactions are present and what is their possible effect on INR?

What recommendation would you make at this time?

Answer 1

1)The monitoring of INR is the key elements in patient with warfarin therapy because the chance for bleeding is high in patient is on warfarin treatment.

The targeted INR value for this patient is (2.0 to 3.0)this is the usual range in the case of venous thrombosis and vulvular heart disease.

2) factors should consider when evaluating the patient

Warfarin therapy is the effective treatments for venous thrombosis and it is a effective anticoagulation agent. Close monitoring is needed for patient with wayfaring because chance of bleeding in beginning is high .

Regular INR value interpretation is needed to evaluate the therapeutic response of patient and find out the factors affecting the value of INR.

Factors affecting INR value

: Diet and alcohol _food that are rich in vitamin K (broccoli,spinach and cabbage) may inhibit the action of warfarin and interfere with INR value.

Consumption of alcohol also interfere the function of warfarin .

:Drug interactions :some drugs such as antibiotics, laxatives and antacid, aspirin and SSRIs interact with warfarin and inhibit the function of warfarin.

:medical illness:the disease condition such as heart failure, hypo and hyperthyroidism ,and liver failure may alter the INR value.

:Dosage alterations :changes in dosage also alter the INR value.

Patient is on warfarin  therapy need close monitoring of signs of bleeding like gum bleeding, heamaturia, Malena etc.

3)drug-drug interactions and effect on INR

Many drugs are interact with warfarin and some of them may alter the value of INR. The major drug interactions are in the case of NR

:Ranitidine__ranitidine is an antacid and it inhibit the metabolism of warfarin and increase chance of bleeding. It interferes with INR value and it show increase in INR value.

:Aspirin___aspirin is interfering with primary haemostasis and increased bleeding risk with out alteration in INR value.

:Terazocine___it will interfere the action of Warfarin and increase chance for bleeding .This interactions will result in 5% increase in INR value

Other drug interactions are

:SSRIs interfere the platelet function and increase bleeding with out elevation inINR value.

:amiodarone inhibit metabolism of warfarin .

:certain antibiotics such as fluconazole and miconazole inhibit the metabolism of warfarin.

:NSAIDs interact with warfarin cause direct mucosal injuries and cause bleeding.

:paracetamol and tramadol also inhibit the metabolism of warfarin.

4)recommendations to this patient

:educate the patient to check the signs of bleeding such as gum bleeding, nose bleeding, Malena, heamaturia and blood in vomits. advise them to should immediately report to the health care personal .

:advice them to avoid food rich in vitamin K and avoid alcoholism.

:advise them to avoid use of over the counter drug, it may interfere with warfarin and cause serious complications .

:Educate them to do not change the dose of warfarin without prescription of consultant.

:schedule them for checking of INR value and next visit at the time of discharge .