MERCY MEDICAL CENTER – SIOUX CITY
INPATIENT WARFARIN DOSINGI. PURPOSE:
The goal of the anticoagulation service is to provide continuity of care to patients who require anticoagulation; enhance patient care through education, monitoring and close follow-up; and reduce adverse events associated with anticoagulation therapy.
II. POLICY:
The department of pharmacy is responsible for the management of warfarin for patients under he order of a prescriber. The pharmacist will order necessary lab work and dosing per protocol.
The department of pharmacy will be responsible for providing warfarin education for all patients.
III. EQUIPMENT:
Cerner Pharmacy Computer System (PharmNet (Med Manager) and PowerChart)
IV. PATIENT TEACHING: N/A
When warfarin is initiated, patients will be given the Introduction to Anticoagulation handout. During their hospital stay they will be given the opportunity to watch the “Coumadin and You” DVD. Prior to discharge, a pharmacist will provide the Patient Information Pamphlet, verbal counseling on warfarin, and answer questions from the patient and/or caregivers. Provision of education will be documented in the patient’s electronic medical record. Nursing will document all education provided in the anticoagulation section of the patient education form. Pharmacists will document education provided as a pharmacy clinical intervention.
V. PROCEDURE:
All patients on warfarin must have a baseline INR before a dose of warfarin is received. A baseline INR is defined as an INR done within the last 72 hours. Pharmacists will verify a baseline INR has been completed before the initial warfarin dose is verified. If a baseline INR is not ordered by the physician the pharmacist shall order an INR per protocol. If a baseline INR was obtained an outside facility, the result will be recorded in PowerChart.
Initiating a request for Pharmacist management of warfarin therapy per pharmacy protocol
The physician must write or give a verbal order or enter an electronic order for “pharmacy to Dose Warfarin”. The order shall also include the desired target INR, the indication for warfarin, and the duration of anticoagulation. If this information is not given, dosing will be based of CHEST guidelines. This order will allow pharmacists to order warfarin and necessary lab work.
Initiation of Therapy
Physicians may request pharmacists to dose warfarin (Coumadin®) according to this protocol, stating in their order the indication for warfarin and the target International Normalized Ratio (INR). Upon receiving such an order, a pharmacist will review the patient’s chart for conditions affecting warfarin sensitivity, coagulation labs, potential drug interactions with warfarin and other medical information pertinent to warfarin dosing. The pharmacist will document in the anticoagulation dosing form and complete a clinical pharmacy intervention daily. All warfarin doses will be administered at 1600. When requests for Pharmacy to Dose Warfarin are received after 1600, the pharmacist will begin dosing of warfarin the next day.
Unless otherwise specified by the physician, the targeted INRs used to guide warfarin therapy will be those recommended by the most recent American College of Chest Physicians (ACCP) Consensus Conference on Antithrombotic Therapy (1). Targeted INRs are:
Indication / INRProphylaxis of venous thrombosis (other than high-risk surgery) / 2.0 – 3.0
Treatment of Deep Vein Thrombosis/Pulmonary Embolism / 2.0 – 3.0
Prevention of systemic embolism
Tissue heart valves / 2.0 – 3.0
Acute Myocardial Infarction (to prevent systemic embolism) / 2.0 – 3.0
AMI (to prevent recurrent MI) / 2.5 – 3.5
Valvular heart disease / 2.0 – 3.0
Atrial Fibrillation / 2.0 – 3.0
Bileaflet mechanical valve in aortic position / 2.0 – 3.0
Mechanical prosthetic valves (high risk) / 2.5 – 3.5
Presence of Lupus Anticoagulant or Antiphospholipid Antibodies / 2.5 – 3.5
Guidelines for Selecting Initial Warfarin Doses
If a patient is admitted on a maintenance dose of warfarin, check the INR. If the INR is therapeutic, continue that maintenance dose.
Otherwise, the initial starting doses of warfarin will be those listed in the following table.
***Pharmacists may select a lower or higher starting dose of warfarin as the patient’s condition or medical history warrants.
Patient Condition / Suggested Daily Warfarin DosePreviously on warfarin / Continue previous regimen if INR is in target range
69 years or younger / 5 mg
DVT prophylaxis following joint replacement / 5 mg
70 years old or older / 4 mg
Impaired nutritional status / 4 mg
Acute or exacerbation of congestive heart failure / 4 mg
High risk of bleeding / 4 mg or less
Selecting a Warfarin maintenance dose
For patients 70 years of age or older, give a fixed initial dose for the first two days of warfarin therapy and then obtain an INR the next morning to guide the selection of a maintenance dose as outlined in the following table.
Suggested algorithm for selecting a warfarin maintenance dose in inpatients 70 years old and older when the target INR is 2.0 to 3.0
If day 3 INR result is: / Suggested maintenance dose is:Less than 1.3 / 5 mg
1.3 to 1.4 / 4 mg
1.5 to 1.6 / 3 mg
1.7 to 1.8 / 2 mg
1.9 to 2.4 / 1 mg
2.5 and higher / Measure INR daily and omit warfarin doses until INR is less than or equal to 2.4
Adapted from Siguret V, Gouin I, Debray M, et al. Initiation of warfarin therapy in elderly medical inpatients: a safe and accurate regimen. Amer J Med 2005;118:137-42.
For patients younger than 70 years old, the following table may be used to guide dosing
Day of Warfarin therapy / INR Value / Dose of Warfarin to giveDay 3 / < 1.5
1.5 – 1.9
2.0 – 2.5
2.6 – 3.0
> 3.0 / Between 5 and 7.5 mg
2.5 – 5 mg
0 – 2.5 mg
0 – 2 mg
No dose
Day 4 / < 1.5
1.5 – 1.9
2.0 – 3.0
> 3.0 / 10 mg
5 – 7.5mg
0 – 5 mg
No dose
Day 5 / < 1.5
1.5 – 1.9
2.0 – 3.0
> 3.0 / 10 mg
7.5 – 10 mg
0 – 5 mg
No dose
Day 6 / < 1.5
1.5 – 1.9
2.0 – 3.0
> 3.0 / 7.5 - 12.5 mg
5 - 10 mg
0 - 5mg
No dose
Management of Elevated INRs
Post-operative patients (including orthopedic surgery patients) – The following guidelines will be used when recommending to physicians the dose of vitamin K needed to reverse excessive anticoagulation.
Warfarin Reversal Guidelines (Adapted from 8th ACCP Consensus Conference on Antithrombotic Therapy)
INR LEVEL
/ SIGNIFICANT BLEEDING /RECOMMENDATION
>TR BUT <5 / NO / •Lower the dose OR•Omit a dose and resume at a lower dose when in TR – monitor more frequently OR
•If only slightly elevated, do nothing
>5 BUT <9 / NO / •Omit the next 1-2 doses, monitor frequently, and resume at appropriate adjusted dose when in TR OR
•Omit a dose and administer 1-2.5mg of vitamin K* orally OR
•If rapid reduction, administer less than or equal to 5mg of vitamin K orally - Can give 1-2mg of vitamin K orally if needed
>9 / NO / •Hold warfarin - administer vitamin K 2.5-5mg orally, monitor INR frequently, re-administer vitamin K as necessary. May resume warfarin at a lower dose once INR is in TR
ANY / YES / •Hold warfarin - administer vitamin K 10mg slow IV infusion supplemented with: fresh frozen plasma, prothrombin complex concentrate, or recombinant factor VII. Repeat vitamin K every 12 hours as needed
ANY / LIFE-THREATENING (ex. Increased ICP) / •Hold warfarin - administer fresh frozen plasma, prothrombin complex concentrate, or recombinant factor VII and give vitamin K 10mg by slow IV infusion - Repeat as indicated by INR value
* Only 5mg scored tablets commercially available (2.5mg is possible but other strengths are not)
If Pharmacy to Dose Warfarin order is discontinued for any reason the patient is no longer a warfarin protocol patient. The physician must re-order the Pharmacy to Dose Warfarin per protocol if she/he wants warfarin managed per pharmacy protocol.
If warfarin is discontinued and re-started using the warfarin protocol, the pharmacist may restart on the previous dose of warfarin if the INR was in the desired therapeutic range prior to being discontinued.
If a patient requires an invasive procedure that necessitates warfarin being held or anticoagulation reversal, the patient will no longer be treated using the protocol.
Management of Warfarin During Invasive Procedures
For emergent invasive procedures, vitamin K can be used to reverse effects of warfarin (see above). The following recommendations are from ACCP1:
Risk of thromboembolism / Recommended procedureLow risk (no thromboembolism for > 3 months, atrial fibrillation patients without a history of stroke or other risk factors, and bileaflet mechanical cardiac valve in aortic position) / Stop warfarin approximately 4 days before surgery, allow INR to return to near-normal level, briefly administer post-op prophylaxis (if the intervention itself creates a higher risk of thrombosis) using heparin 5,000 units subcutaneously or a prophylactic dose of enoxaparin and simultaneously begin warfarin therapy; alternatively, a low dose of unfractionated heparin (UFH) or a prophylactic dose of low molecular weight heparin (LMWH) can also be used preoperatively.
Intermediate risk of thromboembolism / Stop warfarin approximately 4 days before surgery, allow the INR to fall, cover the patient with heparin 5,000 units subcutaneously beginning 2 days before surgery or with a prophylactic dose of LMWH, and then commence low-dose heparin (or LMWH) and warfarin postoperatively; some individuals would recommend a higher dose of heparin or a full dose of LMWH in this setting
High risk of thromboembolism
(Patients with recent [< 3 months] history of DVT, or mechanical cardiac valve in the mitral position or an old model of cardiac valve [ball/cage]) / Stop warfarin therapy approximately 4 days before surgery, allow INR to return to normal, begin therapy with full-dose heparin or full-dose LMWH as the INR falls (approx 2 days before surgery). heparin infusion should be discontinued 5 hours before surgery with the expectation that the anticoagulant effect will have worn off at the time of surgery; it is also possible to continue with subcutaneous heparin or LMWH and to stop 12-24 hours before surgery with the expectation that the anticoagulant effect will be very low or have worn off at the time of surgery
Low risk of bleeding / Continue warfarin therapy at a lower dose and operate at an INR or 1.3 to 1.5, an intensity that has been shown to be safe in gynecologic and orthopedic surgical patients; the dose of warfarin can be lowered 4 or 5 days before surgery; warfarin therapy can then be restarted postoperatively, supplemented with a low dose of UFH (5000 units subcutaneously) or a prophylactic dose of LMWH (enoxaparin) if necessary
Adapted from Table 8 in: the Seventh ACCP Conference on Antithrombotic and Thrombolytic Therapy. Chest 2004 (suppl) 126:214S-215S.
Management of enoxaparin (Lovenox ®), fondaparinux (Arixtra ®) or unfractionated Heparin (UFH) when used
in combination with Warfarin.
It is commonplace to use either unfractionated heparin (UFH) or a low molecular weight heparin (LMWH) (e.g. enoxaparin (Lovenox ®), in combination with warfarin in order to provide an immediate anticoagulant effect until the warfarin regimen reaches a target therapeutic INR. This protocol authorizes the pharmacist to discontinue any concurrent UFH or LMWH once the INR has been in the desired target range for two consecutive days and the patient has received at least five total days of heparin or LMWH therapy and heparin or LMWH will not be discontinued before three days of bridge therapy.
Frequency of INR Monitoring
INRs will be obtained daily. Once the INR is in the desired target range for two or more consecutive days, the frequency of INR monitoring may be reduced.
Discharge
An appointment for a follow-up INR should be made prior to discharge and communicated to the patient. Information regarding the doses the warfarin received will be sent to the provider that will be managing anticoagulation the patient after discharge.
VI. PHARMACEUTICAL WASTE MANAGEMENT:
Warfarin is a P-Listed Pharmaceutical Waste (acutely hazardous waste) and will be identified with a black sticker with a white ”P”. Unused warfarin tablets and the packaging will be wasted to the Black ‘P’ container. The containers and packaging that hold acutely hazardous pharmaceuticals must be collected as hazardous waste.
VII. DOCUMENTATION:
When pharmacy is dosing warfarin the pharmacist will complete a clinical pharmacy intervention daily. The initial day of warfarin therapy the pharmacist will compete the warfarin dosing by Rx intervention. Each day after the initial day, the pharmacist will complete a follow up warfarin intervention form.
VIII. DEFINITIONS: N/A
IX. REFERENCES:
Seventh ACCP Conference on Antithrombotic and Thrombolytic Therapy. Chest 2004 (suppl) 126:214S-215S.
Siguret V, Gouin I, Debray M, et al. Initiation of warfarin therapy in elderly medical inpatients: a safe and accurate regimen. Amer J Med 2005;118:137-42.
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