2. Anticoagulants Setting the Scene Amanda Powell and Sue Wooller May 2014

3. Coroner highlights prescribing error after patient dies from warfarin overdose BMJ 2002;325:922 Failure to prescribe appropriate prophylaxis against PUD contributes to the death of a patient from a GI bleed whilst anticoagulated MPS - UK Casebook 2005 Fatal outcome of Azapropazone/Warfarin interaction - INR not checked despite early signs of bleeding. Improving Medication Safety - DoH 2004

4. Delay in follow up after 20% increase in Warfarin dosage leads to fatal haemorrhage Improving Medication Safety - DoH 2004 Suprachoroidal haemorrhage after Clarithromycin co-prescribed with Warfarin leaves patient with permanent visual damage Journal of Royal Society of Medicine 2001 Patient dies of a subdural haematoma secondary to a grossly elevated INR having been recently discharged from hospital MPS website

5. Patient, post DVT, had a constantly low INR due to mistaking 0.5mg for 5mg tablets Local incident 2010 Patient, post DVT, given warfarin on only Saturdays and Sundays due to poor discharge communication Local incident 2010 Patient admitted to ITU with life threatening haematoma after continuing on loading dose of warfarin post discharge Local incident 2011

6. Coroner highlights prescribing error after patient dies from warfarin overdose BMJ 2002;325:922  The coroner returned a verdict of accidental death on a 79 year old patient.  The man died of gastrointestinal haemorrhage three weeks after being told to take the wrong dose.  Doctors at the surgery in south east Sheffield used to write repeat prescriptions for the drug by hand, on the basis of the patient’s latest blood test results.  The card would then be handed to the receptionist, who would inform the patient of any required change in dose.  The patient in question was taking doses of 2 mg or 3 mg on alternate days. His doctor wrote the word "Same" on the patient’s card and passed it to the receptionist, who read his writing as "5mg."

7.  Describing the incident as a "disastrous error," the doctor concerned said the surgery has since changed its protocol for repeat prescriptions of the drug.  Blood test results and recommended doses of warfarin are now entered into the computer system by the doctor, the doctor informs the patient by phone the same evening of the result, and confirmation of the dosage is sent in writing to the patient a few days later.  But he added that he had said in the court hearing that his own handwriting was often difficult to read. "I accept entirely in my own handwriting my ‘S’ and my ‘5’ are very similar and my ‘S’ can easily be mistaken for a ‘5’” Coroner highlights prescribing error after patient dies from warfarin overdose BMJ 2002;325:922

8. Nursing home administered 1mg tablets instead of 3mg tablets to a patient resulting in an INR of 1.4 Nursing home administered 2.5mg Warfarin daily instead of 2 1 / 2 tablets of 3mg (7.5mg) daily Patient discharged from CCU with Warfarin dose written in a booklet about medicines for the heart. Took 3 x 5mg daily instead of 3.5mg daily National Patient Safety Agency

9. Local examples There was a patient taking 0.5mg instead of 5mg as the GP had issued 0.5mg and we didn't know he had them - we kept increasing his dose and nothing was happening. Many patients still fail to let us know when they are given new meds/antibiotic courses. Anticoagulant Clinic Pharmacist, UHW

10. Local examples Patient referred to secondary care INR service for switching from phenindione to warfarin due to supply problems Dose had increased over last 4 months from phenindione 120mg bd to 180mg bd (equivalent to 20mg warfarin daily) yet INR still sub-therapeutic On further checking patients phenindione supply had expired several months earlier. Cwm Taf Anticoagulation Service

11. Local examples Patient was slow loaded for AF on 3mg daily for 7 days then re-check INR.  Given 3mg & 1mg tablets.  Took both despite yellow book clearly stating 3mg (1 blue tablet) daily.  INR on Day 8 >15 Patient given 5mg tablets instead of his usual 3mg.  Just thought the colour had changed despite being on warfarin for several years.  INR >8.0 after 1 week. Cwm Taf Anticoagulation Service

12. Local examples Residential home called for advice: Patient had been discharged home from hospital a month previously, had a DVT during admission and had been started on warfarin. Patient had been discharged home on a Saturday and the discharging team advised for the patient to have 3mg of warfarin on the Saturday and Sunday. For the month since being discharged from hospital the nursing home had been giving the patient 3mg of warfarin every Saturday and Sunday, no warfarin during the week and no INR monitoring.

13. Local examples Patient given 2 x 10mg loading doses on the ward  Discharged at a weekend with 1mg, 3mg & 5mg tablets  Continued with 10mg daily until next INR check as thought this was correct  Admitted to ITU with life threatening haematoma after 5 days Cwm Taf Anticoagulation Service

14. A 66-year-old man with ischaemic heart disease was treated with warfarin for AF. He developed acute arthritis, diagnosed as gout by his general practitioner, and was prescribed the anti-inflammatory drug azapropazone. The dose was subsequently increased in response to an exacerbation of his arthritis. The patient then developed signs of bleeding. The general practitioner arranged for a full blood count, but did not check the INR. Before the results were available, the patient suffered a massive intracranial haemorrhage, was admitted to hospital, and died. On admission his INR was greater than 10. Reducing the risks: Oral anticoagulants Improving Medication Safety 2004, DoH

15. An example (UHW) 94 yr old gentleman admitted due to haematuria. Patient on Warfarin for AF (range 2.0-3.0) admitted with INR>22 (vitamin K administered) Had been started on trimethoprim 8 days earlier. GP had taken INR one day after starting course (INR was 4.3) but dose not changed.(according to relative). Patients book was available on admission but no doses were recorded in the book and dates not fully completed. Due to patients age range decreased on discharge (1.5-2.5)

16. Suprachoroidal haemorrhage after addition of Clarithromycin Journal of the Royal Society of Medicine 2001; 94: 583-584 62 year old lady with AVR/MVR anticoagulated with Warfarin target INR 3.0 Attended casualty with sudden deterioration of vision after coughing A week before presentation she had begun a course of Clarithromycin for a chest infection INR 3 days before start of course: 2.3 INR 3 days into the course: 2.9 INR on presentation: 8.2