Guideline: Oral Anticoagulants

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1 Guideline: Oral Anticoagulants Name of patient treated under this guideline: Anticoagulant medications are one of the classes of drugs most frequently identified as causing harm and admission to hospital. Managing the risks associated with anticoagulants can reduce the chance of patients being harmed in the future. The National Patient Safety Agency issued a Patient Safety Alert in 2007 to address ways of reducing the risk associated with anticoagulant therapy. Suggested measures include the use of competencies for all individuals involved in anticoagulant care, written procedures and guidelines for use of anticoagulants, regular audit of safety indicators, appropriate patient information for individuals on anticoagulant therapy at different points in their patient journey, enhanced communication between prescribers, pharmacists and anticoagulant clinics, standardisation of the range of anticoagulant products available and safe practice procedures for the administration of anticoagulants in social care settings. This guidance is incorporated into this document which aims to support the seamless transfer of prescribing from secondary to primary care and to outline arrangements for monitoring in secondary care. It provides an information resource to support clinicians providing care to the patient. This guideline was prepared using information available at the time of preparation, but users should always refer to the manufacturer s current edition of the Summary of Product Characteristics (SPC or data sheet ) for more details. 1.0 Status of Warfarin Warfarin is the most frequently used oral anticoagulant in the United Kingdom. It acts by antagonising the coagulant effect of vitamin K. The activation of the vitamin K dependent clotting factors (II, VII, IX, X) is reduced with resultant prolongation of the clotting times and reduction in risk of thrombus formation. Warfarin therapy is often initiated in secondary care and it is common for it to continue to be prescribed in primary care if arrangements for monitoring in secondary care are confirmed. The key principle is that the GP is provided with information and given the opportunity to accept (or decline) prescribing responsibility before the transfer occurs. 2.0 Licensed Indications Prophylaxis of embolisation in atrial fibrillation and rheumatic heart disease Prophylaxis of valve thrombosis after the insertion of a prosthetic heart valve Prophylaxis and treatment of venous thrombo-embolism (deep vein thrombosis and pulmonary embolism) Dose Warfarin has a narrow therapeutic range. It is monitored by regular blood test monitoring of the INR. A standard loading dose regimen is used ( urgent or slow ) and the dose then adjusted to attain the appropriate target INR. The usual maintenance dose is between 2 and 9mg/day but maintenance doses may vary between 0.5 mg/day and 25mg/day

2 Recommended Therapeutic Ranges for Warfarin INDICATION RECOMMENDED DURATION TARGET INR (& Atrial fibrillation/cva prophylaxis Calf vein thrombosis Proximal DVT/temporary risk factors/low recurrence risk Proximal DVT/ongoing risk factors /idiopathic event Pulmonary embolus Recurrent VTE off warfarin Recurrent VTE on warfarin (INR 2-3) VTE secondary to thrombophilia VTE secondary to Antiphospholipid Syndrome Arterial thrombosis secondary to antiphospholipid syndrome DVT in cancer patients DVT in IV drug abusers DVT in pregnancy Lifelong (or until sinus rhythm restored) REFERENCE/ COMMENT RANGE) 2.5 (2-3) Antiplatelet agents will be stopped when a therapeutic INR is attained unless clearly stated on the referral form that they are to continue in combination with warfarin. At least 6 weeks in 2.5 (2-3) range 3 months in range 2.5 (2-3) OCP/long haul flight/post op now fully recovered. 6 months 2.5 (2-3) 6 months 2.5 (2-3) Lifelong 2.5 (2-3) Lifelong 3.5 (3-4) 6 months 2.5 (2-3) Discuss with Consultant Haematologist. Discuss 2.5 (2-3) Lifelong 3.5 (3-4) Aspirin also recommended. Consider bleeding risk of higher target INR (INR 2-3 may be used). Discuss with - Use LMWH oncologist/haematol ogist 6 months 2.5 (2-3) Consider LMWH as alternative if poor compliance/unstable control. Discuss with haematologist/ obstetrician Use LMWH, usually bd dosing 2

3 Cardioversion 6 weeks pre and 4 weeks post cardioversion or as decided by Cardiologist Cardiac valves if site/type unknown Peripheral arterial disease/grafts Coronary artery disease Mural Thrombosis post MI 2.5 or 3.0; may use 3.0 ( ) prior to procedure to minimise cancellations Lifelong 3.0 ( ) aortic valves 3.5 (3-4) mitral valves Type and position of valve must be ascertained. In the interim period when a patient is admitted these reference values may be used. Lifelong 2.5 (2-3) Antiplatelet drugs are 1 st line for secondary prophylaxis. If long term anticoagulation is given to patients at high risk of graft failure, an INR target 2.5 and aspirin are recommended. Lifelong 2.5 (2-3) Limited indications discuss all cases with Consultant Cardiologist. 3 months 2.5 (2-3) Particularly high risk patients are those with Mural Thrombosis in presence of LV aneurysm. Cardiomyopathy Lifelong 2.5 (2-3) 3.0 Patient Selection As indicated above. 4.0 Safety Issues 5.1 Contra-indications (see BNF or SPC) Pregnancy Active/ recent peptic ulcer Severe hypertension Bacterial endocarditis 5.2 Cautions (see BNF or SPC) Hepatic or renal impairment Recent surgery Breast feeding 5.3 Common Side Effects (See BNF or SPC) Haemorrhage 3

4 5.4 Less common side effects Skin reactions including ulceration Hair loss Diarrhoea Jaundice Nausea and vomiting Skin necrosis Hypersensitivity Unexplained drop in haematocrit Purple toes Hepatic dysfunction Pancreatitis 5.5 Drug Interactions (see BNF or SPC) and Appendix 6 Drugs that may increase the effect AMIODARONE: This drug will significantly increase sensitivity to warfarin and will require reduction in dose of warfarin or reduced dose induction regimen if warfarin to be commenced on treatment. Reduce warfarin dose and check INR within 5 to 7 days of starting treatment or changing dose of treatment Other drugs: allopurinol, anabolic steroids, capecitabine, chondroitin, chloramphenicol, cimetidine, ciprofloxacin, clarithromycin, cotrimoxazole, erythromycin, danazol, dextropropoxyphene, disulfiram, fibrates, fluconazole, fluorouracil, glibenclamide, ifosfamide, imatinib, isoniazid, itraconazole, ketoconazole, methylphenidate, metronidazole, miconazole, mirtazepine, NSAIDs, omeprazole, roguanil, propafenone, ritonavir, rosuvastatin, simvastatin, sodium valproate, SSRIs, suphonamides, tamoxifen, thyroxine, tolbutamide, venlafaxine,voriconazole Complementary/ alternative medicine: devil s claw, ginko biloba Food and drink: alcohol (in large quantities), grapefruit juice Drugs that have an unpredictable effect on warfarin Drugs: Coenzyme Q10, colestyramine, corticosteroids, phenytoin, antibiotics Food and drink: Cranberry juice Drugs that may decrease the effect of warfarin Drugs: acictretin, aminoglutethamide, azathioprine, carbamezepime, chlordiazepoxide, griseofulvin, mercaptopurine, oral contraceptives, Phenobarbital, rifampicin, sucralfate, vitamin K Complementary/ alternative medications: ginseng, St John s wort Food and drink: alfalfa This is not an exhaustive list. Please refer to the BNF. Always check INR within 5 to 7 days of starting or stopping an interacting treatment or changing dose of treatment. Depending on the mechanism, interactions may take days to weeks to manifest and may persist for a similar length of time after stopping the interacting drug. Careful monitoring of the INR during this time will be required. 5.5 Pre-treatment Assessment Full blood count and coagulation screen. U&Es and LFTs to check renal and liver function 5.6 Routine Safety Monitoring FBC, clotting screen, U+E, LFT prior to starting treatment Urgent Anticoagulation Protocol (Appendix 3): check INR daily for 4 days, then as indicated by the Fennerty algorithm and then weekly until INR stable. In acute venous thrombo-embolism, low molecular weight heparin therapy should be administered daily until the INR is > 2 for at least 2 days and should continue for at least 6 days Slow Anticoagulation Protocol (Appendix 4): check INR after 5 days, then weekly until INR stable. The maximum interval between INR tests should not exceed 3 months 4

5 6.0 Role of Prescriber (Primary or Secondary Care) To assess the suitability of the patient to be commenced on warfarin To carry out initial investigations and safety monitoring. To explain the indication for treatment, possible side effects of the medication, potential drug interactions and need for regular blood test monitoring to the patient and complete the Trust standard counselling form (Appendix 2) To provide the patient with a patient held record pack and information about warfarin (DOH yellow folder) To initiate therapy with warfarin. To write to GP (if secondary care prescriber) enclosing a copy of the guideline requesting that a shared care agreement be initiated. To arrange for appropriate follow up in the anticoagulant clinic by direct communication with the clinic (fax or telephone). It is the responsibility of the prescribing physician to ensure that this first appointment for a blood test in the anticoagulant clinic is made and monitoring arrangements are communicated to the patient To decide when to stop therapy 7.1 Referral to the Anticoagulant Clinic All patients commenced on warfarin or requiring initiation of warfarin should be referred to the anticoagulant clinic at RHCH (unless GP practice undertakes their own service). It is the responsibility of the health care professional initiating the warfarin therapy to ensure that the patient has been counselled about warfarin therapy. For in-patients, counselling should be done prior to the first dose, at discharge and again at the first anticoagulant appointment. For outpatients full counselling should be done by the prescribing doctor or, for those patients referred to the anticoagulant clinic for initiation of treatment, the Anticoagulant Practitioner. The Trust standard counselling form for full counselling should be completed at the time of initiation of treatment and should be retained in the patient s notes (Appendix 2). The Trust standard anticoagulant referral form should be completed and sent to the clinic by fax or post (Appendix 1) The following information should be included in the referral o Name o DOB o Hospital number o Telephone number o Address o GP and prescribing doctor details o Indication for treatment o Target INR o Duration of treatment o Past medical history and list of medications o Date of initiation of warfarin and last 3 INRs (where appropriate) 7.2 Role of Anticoagulant Clinic To provide a safe monitoring service for patients on oral anticoagulant therapy. To interpret the INR result, make dose adjustments to warfarin therapy to achieve the target INR, and to arrange follow-up monitoring test at an appropriate interval. To communicate the dose of warfarin and follow-up date to the patient by posting back the patient held record book. To communicate significant changes in dose, dose instructions for all new patients on warfarin and out of range INR results where appropriate to patients or carers directly by telephone. To communicate with GPs in the event of significant over-anticoagulation (INR > 8) with a view to consideration of prescription of vitamin K where appropriate (Appendix 5), and in the event of concerns about compliance. To communicate in writing changes in dose of oral anticoagulant therapy for patients in care homes To refer patients with difficult/ brittle anticoagulant control, persistent over or under-anticoagulation and patients on unusually high or low maintenance doses of warfarin (< 1mg or >20 mg) to the Consultant Haematologist for further advice. 5

6 To provide advice for clinicians on warfarin therapy as required with the support of the Haematology Consultants. 8.0 Role of GP To accept care in writing as proposed and to ensure that all relevant staff within the practice are aware of the guideline following hospital initiation. To provide prescriptions for warfarin. The GP must review the patient held record book to ensure regular INR monitoring before writing a prescription. To consider any side-effects reported by the patient and discuss with the anticoagulant clinic if action is uncertain. To arrange an urgent INR, FBC and inform the Anticoagulant Clinic in the event of bleeding symptoms. To avoid the drug interactions indicated in Section 5.5 and current BNF. To inform the Anticoagulant Clinic if any problems arise relating to warfarin. To review the patient on an annual basis to assess that there is an ongoing indication for treatment, to review anticoagulant control, any adverse incidents and change in clinical condition and to communicate any change of circumstances to the Anticoagulant Clinic. Where compliance aids are being used, up to date information regarding the latest prescribed dose must be supplied community pharmacist involved. For patients under the care of the Anticoagulant Clinic at the Royal Hampshire County Hospital, arrangements must be made to inform the Anticoagulant Practitioner of these special contact arrangements. The current INR, warfarin dosage and next INR test date can then be faxed to the community Pharmacy (+/- GP surgery) following every INR test. 9.0 Role of Patient To read the information provided in the oral anticoagulant pack. To take warfarin at the dose recommended by the Anticoagulant Clinic. To attend for regular blood tests at the recommended time with the (yellow) patient held record book. To attend annually for review by the GP. To report any side effects, abnormal bruising or bleeding to the GP or Anticoagulant Clinic. To report any changes in medication, hospital admissions or discontinuation of treatment to the Anticoagulant Clinic. The patient must fully understand the need for safety monitoring whilst on warfarin Further information WEHT Haematology Consultant: WEHT Anticoagulant Co-ordinator: WEHT Medicines Information: Authorisation Produced by: Updated by: Approved by: Winchester and Southampton District Prescribing Committee (Martin Stephens, Chairman), plus local specialist departments. Date of August 2008 production: Date for review: August

7 PROFORMA Title of document: (Delete / Add document types as appropriate) Author: (Name & Position) Search Engine Keywords: (Words you think staff will use to search for this document) Related links: (E.G. Websites, SUHTranet pages, other documents) Description: Guideline; Warfarin; oral anticoagulants Guideline: Oral Anticoagulants Final Validation Committee: Date agreed: (can be manually added when document validated) Accountable Officer: (Name & Position) Responsible Officer: (Name & Position) Directorates who use the document: District Prescribing Committee Date sent to Policy Administrator: (can be manually added when document validated) Medicine Highlighted to: (Key staff, Departments, Directorates) Date doc. implemented in WEHCT: PCT, LMC, GPs Dec-08 Date of next review: Aug-11 Date doc. loaded on Intranet: Date(s) Reviewed (if applicable): Details of most recent review: (Outline main changes made to document) Initial version Signature of Chairman of Validation... Committee: Print Name:... Post Held:... Date:... 7

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9 Appendix 3 Urgent Warfarin Loading Schedule Urgent anticoagulation Day INR Warfarin Dose (mg) One < (5mg if high risk of sensitivity to warfarin) Two < (5mg if high risk of sensitivity to warfarin) > Three < (5mg if high risk of sensitivity to warfarin) >4.0 0 Four (predicted <1.4 >8 maintenance) Miss out next day s dose then give 2mg >4.5 Miss out two day s doses then give 1mg Guidelines on oral anticoagulation: third edition. British Journal of Haematology 101 (2), doi: /j x If INR not therapeutic by day 7, contact haematology.

10 Appendix 4 SLOW PROPHYLACTIC ANTICOAGULATION FOR AF For patients who do not require rapid anticoagulation, a slow non-loading regimen is safe and achieves therapeutic anticoagulation in the vast majority of cases over 3-4 weeks. This avoids the problems of over-anticoagulation and bleeding associated with rapid loading and requires less frequent monitoring in most cases. Patients should be commenced on 3mg warfarin daily (unless they have risk factors such as liver disease, cardiac failure, bleeding risks) and INR taken after 5 days (after 4 days for high risk patients). Aspirin should be started concurrently with warfarin and continued until the INR is therapeutic. Rapid anticoagulation may be required for urgent cardioversion or as indicated by the Cardiologist. In such cases, heparin cover may be needed in conjunction with the rapid DVT / PE loading regimen.

11 Appendix 5 Recommendations for management of bleeding and excessive anticoagulation (from BCSH Guidelines) INR (target ) or INR (target ) INR No or minor bleeding INR > 8.0 No or minor bleeding Stop warfarin or reduce dose Restart warfarin when INR<5.0 Stop warfarin Restart warfarin when INR <5.0 Stop warfarin Restart warfarin when INR <5.0 If other risk factors for bleeding, give mg vitamin K po Major bleeding (any INR) / Life threatening bleeding Stop warfarin Dial 999 refer to hospital

12 Appendix 6 Common Warfarin Drug Interactions AVOID Aspirin Analgesics Antifungals NSAIDS Others Except where combination specifically indicated e.g. mechanical valve prosthesis, recurrent thrombosis Co-proxamol, Ketorolac (post operative) Miconazole Azapropazone Cranberry juice, Glucosamine ADJUST DOSE (Speak to Pharmacist) Ulcer Healing Antiarrthymics Lipid Lowering Antiepileptics Antibiotics/antifungals Thyroid Gout Others Cimetidine Amiodarone,Propafenone Bezafibrate, Fenofibrate Carbamazepine Aztreonam, Fluconazole, Voriconazole,Metronidazole, Rifampicin, Cotrimoxazole Carbimazole,Levothyroxine Allopurinol, Sulphinpyrazone Ciclosporin,Mercaptopurine, Oral Contraceptive Steroids, Barbiturates,Tamoxifen MONITOR INR Antiarrhythmics Lipid Lowering Antidepressants Antiepileptics Analgesics Antibiotics/antifungals Antivirals NSAIDS Ulcer Healing Drugs Quinidine Ezetimibe, Cholestyramine and Statins SSRIs,Venlafaxine Phenytoin Tramadol Ketoconazole, Erythromycin, Azithromycin, Clarithromycin, Penicillins,Ciprofloxacin, Levofloxacin Ritonivir, Saquinavir, Indinavir, Nevirapine Celecoxib, Etoricoxib, Ibuprofen, Mefenamic acid, Diclofenac Esomeprazole, Omeprazole and Lansoprazole Others Bicalutamide, High dose Dexamethasone, Methylprednisolone,Influenza vaccine, Omacor, Flutamide, Grapefruit juice, Hydrocodone, Leflunomide, Sucralfate, Diflunisal, Dipyridamole * This list is not exhaustive: If in doubt consult latest edition of the BNF

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