Anticoagulants
Setting the Scene
Amanda Powell and Sue Wooller
May 2014
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
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
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
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."
Coroner highlights prescribing error after patient
dies from warfarin overdose
BMJ 2002;325:922



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’”
National Patient Safety Agency



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 21/2
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
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
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
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
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.
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
Reducing the risks: Oral anticoagulants
Improving Medication Safety 2004, DoH







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.
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)
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