managing warfarin drug interactions: the bayview experience dawn users group, november 2002 charles...
TRANSCRIPT
Managing Warfarin Drug Interactions: The Bayview Experience
DAWN Users Group, November 2002
Charles H. Twilley, MBA, PharmDJohns Hopkins Bayview Medical Center
Baltimore, MD USA
Where is Maryland?
USA
The capital of the state
Where is Baltimore?
Salisbury is REALLY the cultural epicenter of the state!
Where in Baltimore is Bayview?
Bayview Overview
• Community Teaching Hospital
• Member Institution of Johns Hopkins Healthcare
• 692 beds– 320 acute care– 255 long term/geriatric– 117 rehabilitation/transitional care
The Anticoagulation Service At Bayview
• Clinical Initiative of the Department of Pharmacy Services
• Occupies 1 FTE• Responsible for all aspects of chronic
anticoagulation management, including acute bridge therapy with heparin, outpatient DVT Tx.
• Currently has 625 patients on service; up from 285 in 1998
JHBMC Patient Breakdown by Diagnosis
33%
15%11%
10%
10%
21% Atrial fibrillation
Prosthetic HeartValves
DVT
Cardiomyopathy
Embolic CVA
Other
JHBMC Patient Breakdown by Diagnosis
Patient Volume
0
100
200
300
400
500
600
Date
Vo
lum
e PatientVolume
PATIENT VOLUME
Problems with Anticoagulation Management at Bayview
• No formalized inpatient management service– approval slated for November, 2002
• Difference in level of pharmaceutical care between acute and long term care
• JHBMC is a teaching facility
• Large geriatric population
Magnitude of the Problem
• Warfarin associated 22% of adverse drug reactions in Q3 FY 2000-2001
• Heparin is associated with 51% of medication errors for Q1-Q3 FY 2000-2001
• Problems with anticoagulation management implicated in two sentinel events over the past 16 months
• Adverse Drug Events (ADE’s) are associated with cost of $7000 per event (1997 study finding)
Case Study
• CJ: 48 y.o. AA male, s/p cadaveric renal transplant, developed embolic CVA
• chronically anticoagulated for 4 years
• Presented to PCP with painful, discolored, cracking of great toe; diagnosed as onychomycosis
• Treated with itraconazole 100mg po qd
Case Study: 14 days later
• Presents to AC clinic• Pertinent findings
– INR 18.5 (repeated and verified)– Hgb/Hct: 7.5/22– Guiac: +
• When asked why– neither my doctor nor the pharmacist that filled
the prescription thought it would be a problem
The final outcome
• Three day admission
• 4 units PRBC’s transfused
• Cost to the health care system of $5000-7000
• ? Cost in lost productivity, work time, etc.
• Could this have been avoided?
What could the ACS do?
• Prevent admissions from outpatients served
• Instill the notion of drug interactions into introductory didactic patient education
• Implement specific, evidence-based policies and procedures to address management
• Utilize management database to facilitate
How did the ACS utilize DAWN AC?
• Utilized the drug interactions screen function
• incorporated Drug Interaction algorithm into interaction tracking function
• provided prescriber with notification of interaction and cited literature
How did we test our results?
• Identified drug interactions with clinically relevant evidence of severity– chose drug with Evidence Levels I and II of
clinical significance (Wells, et al.)
• Evaluated efficacy of our ACS to prevent/minimize warfarin interactions
• Conducted prospective evaluation from 07/01/99 to 01/01/2000 to evaluate efficacy
Frequency of Potentially Interacting Drugs
NSAID's3%
Cimetidine5%
Omeprazole5%
Fluconazole7%
Metronidazole8%
Cotrimoxazole15%
Ciprofloxacin22%
Amiodarone26%
Erythromycin3%
Carbamazepine3%
APAP3%
n=59
Time Course from Therapy Initiation to Notification of Anticoagulation Service
3-7 days after 1st dose23%
1-3 days after 1st dose32%
Prior to first dose34%
Prior to treatment8%
>7 days after 1st dose3%
n=59
Type of Intervention
Dose Alteration
Repeat PT within 72 hrs
None Alternative Therapy
(10 %)
(43 %)
(58 %)
(18 %)
n=59
Results
Therapeutic
Subtherapeutic
Supratherapeutic
Additional Pt
50 % of patients
20 % of patients
27 % of patients
27 % of patients
n=59
ResultsFrequency of InteractingTherapy
59 cases (23.5 events/100patient years)
Frequency of PotentiallyInteracting Drugs (n)
Amiodarone (n=15);Ciprofloxacin (n=13);Cotrimoxazole (n=9)
Time Course from TherapyInitiation to ACS Notification(n)
Prior to treatment (n=5); Prior toFirst Dose (n=20); 1-3 Daysafter First Dose (n=19); 3-7Days after First Dose (n=14); >7 Days after First Dose (n=1)
Type of Intervention fromService (Interventions areadditive)
Alternative therapy (n=6); DoseAlteration (n= 25); No dosechange (n=18); Additional pTmonitoring (n=34)
Effect on Prothrombin Time(INR)
Within therapeutic range (n=31);Subtherapeutic (n=12);Supratherapeutic (n=16)
Adverse Clinical Outcomes Bleeding (n=4)
Clinical Adverse Outcomes# Type of Adverse
EventTime Frame inwhich ACS was
informed
Clinical Sequellae
1 Bleeding >7d after 1st dose Gross hematuriawhich resolved withp.o. vitamin K
2 Bleeding 3-7d after 1st dose Inpatient admissionfor treatment of INRand CHFexacerbation
3 Bleeding 3-7d after 1st dose 24 hr ED visit forobservation andvitamin K
4 Bleeding 3-7d after 1st dose Prolonged inpatientadmission; multipletransfusions
Conclusions
• Potential interactions with warfarin occur at a rate of 23.5 events/100 patient years
• A defined algorithmic approach can minimize the incidence of supratherapeutic INR’s, thus minimizing adverse clinical events.
• Provider notification and intervention within 72 hours after a potentially interacting medication is started may reduce the risk of major bleeding. Patients need to be continually reminded to inform their anticoagulation care provider when new medications are initiated.
Added Benefits
• Problem:– JHBMC was showing $6M in laboratory fees
not retrieved
• Solution:– modify DAWN AC database to create link
between patient demographics
Net Result
• Created a centralized database for billing department
• Created a template for other clinical services
• Able to retrieve $1.8M of $6M deficit
What else?
• Induction regimen function to facilitate ambulatory DVT treatment
• Report writing capabilities
• Database management/query abilities
• Screens for monitoring/preventing adverse drug outcomes
The Bayview Experience
• Facilitated expansion from 285 to 625 patients
• Facilitated ability to capture workflow fluctuations
• Facilitated ability to capture clinical interventions
Future Initiatives
• Use of induction module to undertake inpatient ACS
• use of hand held technology to make ACS a “mobile” clinical entity
• further expand outpatient clinical pharmacy services– Lipid management, diabetes management
