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Quality of anticoagulation and use of warfarin-interacting medications in

long-term care

Madeleine VerhovsekBahareh Motlagh Mark A Crowther

Courtney Kennedy Lisa Dolovich

Glenda CampbellLuqi Wang

Alexandra Papaioannou

BMC Geriatrics July 2008, 8:13

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Background

• Studies have found that warfarin therapy is generally poorly controlled in community settings

[Arch Intern Med 1994; 154(17), Arch Intern Med 2000; 160(7)]

• In long-term care facilities optimal anticoagulation should be achievable:

• Availability of laboratory monitoring • Ensured adherence to warfarin therapy• Infrastructure for dose adjustment• Ability to detect all potential medication interactions

Verhovsek et al. BMC Geriatrics 2008, 8:13

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Primary Objective• Determine how effectively warfarin was

administered to a cohort of residents in LTC facilities

Secondary Objective• Identify the proportion of residents prescribed

warfarin-interacting drugs

What were the objectives?

Verhovsek et al. BMC Geriatrics 2008, 8:13

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• Chart review of 105 residents in five LTC facilities in Hamilton, Ontario

• All residents were on warfarin therapy

• Data collected:• INR levels• Warfarin prescribing and monitoring practices• Use of interacting medications

What methods were used?

Verhovsek et al. BMC Geriatrics 2008, 8:13

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What are the residents’ characteristics?

Percentage of residents on warfarin – 9%

Gender - 72% female

Mean Age - 83.6 yrs (range 54.7-98.0 yrs)

Mean BMI (kg/m2) - 24.9 (range 14.8-37.9)

Verhovsek et al. BMC Geriatrics 2008, 8:13

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How often were residents in therapeutic range?

Sub-therapeutic Therapeutic Supra-therapeuticINR:≤ 1.5 1.6-1.9 2.0-2.5 2.6-3.0 3.1-3.5 ≥ 3.5

Verhovsek et al. BMC Geriatrics 2008, 8:13

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What about medication interactions?

Medication No. (%)

Acetaminophen

Citalopram

Acetylsalicylic acid

Diltiazem

Simvastatin

Levofloxacin

Phenytoin

Ciprofloxacin

Sertraline

Cotrimoxazole

Metronidazole

Clarithromycin

Amiodarone

Amoxicillin-clavulinate

Miconazole

Propranolol

Fluvoxamine

42 (40%)

26 (25%)

17(16%)

12 (11%)

10 (10%)

8 (8%)

7 (7%)

5 (5%)

5 (5%)

3 (3%)

3 (3%)

3 (3%)

3 (3%)

2 (2%)

1 (1%)

1 (1%)

1 (1%)

• 79% of residents (83 residents) were prescribed at least one interacting drug during period of chart audit

• Average of 1.8 interacting medications per resident over duration of chart review (range 1-6)

• 82% of the time (59/72) INR was

checked within ≤7 days after

initiation of medication or change

in dose

• 72 instances of newly initiated medications or dosage changes

Verhovsek et al. BMC Geriatrics 2008, 8:13

What did we conclude?

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INR was in therapeutic range 54.1% of time

INR was sub-therapeutic over one-third of time•

Majority of residents were on medications known to interact with warfarin

20% of the time, INR was not measured within ≤7 days after initiation or change in medication dose

Verhovsek et al. BMC Geriatrics 2008, 8:13

AcknowledgmentsThis work was funded by :

Canadian Institute of Health Research Medical Pharmacies Group Ltd. Regional Medical Associates

Verhovsek et al. BMC Geriatrics 2008, 8:13