Anticoagulation

Question 1

Apixaban DOSES
For the prophylaxis of stroke and systemic embolism in adults with non-valvular atrial fibrillation and at least one risk factor, such as previous stroke or transient ischaemic attack, symptomatic heart failure, diabetes mellitus, hypertension, or age 75 years and over:
The recommended dose is __
When should the dose be reduced?

Answer 1

5mg OD
Dose should be reduced to 2.5 mg BD in people with:
1. At least 2 of the following characteristics:
- age 80 years or over,
- body weight 60 kg or less,
- serum creatinine 133 micromol/L or over.
2. Creatinine clearance (CrCl) 15–29 mL/minute.
Treatment is usually long term.

Question 2

Apixaban DOSES
For the treatment of deep vein thrombosis (DVT) and pulmonary embolism (PE):
The recommended dose is _____
What should be minimum duration?

Answer 2

For the tx DVT PE: 10 mg BD for first 7 days, followed by 5 mg BD.
Duration <= transient risk factors (for example, recent surgery, trauma, and immobilization), but it should be for a MINIMUM of 3 months.

Question 3

Apixaban DOSES
For the prophylaxis of Recurrent DVT and PE in adults (following completion of 6 months of anticoagulation treatment): __________
For the prophylaxis of venous thromboembolism (VTE) in people who have undergone hip replacement surgery: ___________
Prophylaxis of VTE in people who have undergone knee replacement surgery: __________

Answer 3

Prophylaxis recurrent DVT and PE in adults (after 6 months of anticoagulation treatment):
= 2.5 mg BD.
Prophylaxis VTE for hip replacement surgery:
= 2.5 mg BD for 32–38 days, started 12–24 hrs after surgery.
Prophylaxis of VTE for knee replacement surgery:
= 2.5 mg BD for 10–14 days, started 12–24 hrs after surgery.

Question 4

What are the contraindications and cautions for apixaban?

Answer 4

• preg / breast feeding
• Creatinine clearance (CrCl) < 15 mL/minute.
• Liver disease; coagulopathy and bleeding risk.
• A prosthetic heart valve
• Antiphospholipid syndrome — ^ ! recurrent thrombotic events.
• Active bleeding.
• People with a significant risk of major bleeding

Question 5

Apixaban - if spontaneous bleeding occurs and does not stop, or recurs
- sudden severe back pain

Answer 5

Seek immediate medical advice
back pain = retroperitoneal bleeding
This includes bruising, bleeding gums, nosebleeds, prolonged bleeding from cuts, blood in the urine or stools, haemoptysis, subconjunctival haemorrhage, and vaginal bleeding in a postmenopausal woman.

Question 6

specific reversal agent indicated for adults treated with a direct factor Xa (FXa) inhibitor (apixaban or rivaroxaban) when reversal of anticoagulation is needed due to life-threatening or uncontrolled bleeding.

Answer 6

Andexanet alfa (Ondexxya®)

Question 7

Other adverse effects of apixaban include:
Common —
Uncommon —

Answer 7

Other adverse effects of apixaban include:
Common — anaemia, bruising, nausea, and skin reactions.
Uncommon — angioedema, erythema multiforme, hypotension, post procedural haematoma, thrombocytopenia, and wound complications.

Question 8

apixaban x nsaid

apixaban x anticoagulants / antiplatelets

Answer 8

bleeding risk

Question 9

apixaban x strong CYP 450 and PGP inhibitors

Answer 9

Strong inhibitors of both cytochrome P450 3A4 (CYP3A4) and P-glycoprotein (P-gp), such as itraconazole, ketoconazole, and HIV protease inhibitors (for example ritonavir) — plasma concentration of apixaban is increased by these drugs.

Question 10

For drugs that are not considered strong inhibitors of both CYP3A4 and P-gp, such as amiodarone, clarithromycin, diltiazem, fluconazole, quinidine, and verapamil, the plasma concentration of apixaban is

Answer 10

For drugs that are not considered strong inhibitors of both CYP3A4 and P-gp, such as amiodarone, clarithromycin, diltiazem, fluconazole, quinidine, and verapamil, the plasma concentration of apixaban is increased to a lesser extent. No dose adjustment for apixaban is required with these drugs, but the person should be monitored for signs of bleeding or anaemia.

Question 11

apixaban x Strong inducers of both CYP3A4 and P-gp, such as _

Answer 11

Strong inducers of both CYP3A4 and P-gp, such as carbamazepine, phenytoin, rifampicin, and St John’s Wort — plasma concentration of apixaban may be reduced by these drugs.

Question 12

apixaban x ssri / snri / venlafaxine

Answer 12

SSRI (citalopram), SNRI (duloxetine), and venlafaxine — possible ^ risk of bleeding.
The manufacturer of apixaban advises to avoid.
If concurrent use is indicated, monitor for signs of bleeding and anaemia

Question 13

Switching from warfarin to apixaban:

Answer 13

STOP warfarin, and measure INR:
INR < 2, start apixaban.
INR 2 - 2.5, start apixaban the next day.
INR > 2.5, wait until the person’s INR has dropped to less than 2 before starting apixaban.

Question 14

Switching from apixaban to warfarin:

Answer 14

START warfarin, but do not stop apixaban.
- After at least 2 days with warfarin and apixaban, measure INR prior to next scheduled dose of apixaban.
=> INR in target range, stop Apix and continue warfarin.
=> INR not in target range, continue BOTH until INR is in the target range, then stop apixaban.
- Warfarin has a slow onset; 5–10 days before INR is within range.
After tx with apixaban has stopped:
Measure INR after 24 hours
Monitor INR closely (once a week) in the first month of warfarin tx until the person has THREE consecutive stable INR values (for example between 2–3).

Question 15

Switching from apixaban to another direct-acting oral anticoagulant (DOAC):

Answer 15

STOP apixaban
START the new DOAC (dabigatran, edoxaban, or rivaroxaban) when the next dose of apixaban is due.
- If higher than therapeutic plasma conc. are expected, e.g impaired renal function, a longer interval in between DOACs is recommended.

Question 16

Switching from another DOAC to apixaban:

Answer 16

STOP DOAC (dabigatran, edoxaban, or rivaroxaban), 
START apixaban when the next DOAC dose is due.
- If higher than therapeutic plasma conc. are expected, e.g impaired renal function, a longer interval in between DOACs is recommended.

Question 17

Should apixaban be stopped if surgery or dental treatment is required?

• surgery / invasive procedure
• minor surgical procedure with minor bleeding
• low bleeding risk
• high bleeding risk

Answer 17

May need to stop <= risk of thromboembolic event and bleeding risk.

• Minor surgery/risk (performed 12–24 hrs after last dose); do not to interrupt oral anticoagulation. Could practically have intervention scheduled 18–24 hrs after last dose of apixaban is taken, then restart apixaban 6 hours later. So one dose of apixaban may be missed.
• Low bleeding risk, apixaban should be stopped at least 24 hours before the procedure. If CrCl is 15–29 mL/minute, stop Apixaban 36 hrs before procedure.
• HIGH bleeding risk, stop 48 hrs before procedure.

Question 18

INR monitoring in apixaban regimen

Answer 18

No need to monitor INR; however, regular follow up and monitoring is recommended.

Question 19

Apixaban

• Start of apixaban tx tests
• monitoring

Answer 19

At the start of treatment
baseline clotting screen, RFT and LFT, FBC
Repeat the FBC, RFT, LFT yearly for most people.

Question 20

Apixaban tx started review time

Answer 20

Once tx has started, review the person on a regular basis, preferably after 1 month initially and at least every 3 months thereafter. Follow-up intervals may be longer (up to every 6 months) or shorter (eg every month) depending on patient factors, such as renal function, age, and comorbidities.

Question 21

Repeat the FBC, RFT, LFT yearly for most people on Apixaban but what if pt is:

• old and frail
• CrCl
• intercurrent illness that may impact renal/hepatic function

Answer 21

If the person is frail or > 75 years, repeat the blood tests every 6 months.
If the person has a creatinine clearance (CrCl) less than 60 mL/minute, the frequency of monitoring (in months) can be guided by the CrCl divided by 10. For example, every 3 months if CrCl is 30 mL/minute.
If the person has an intercurrent illness that may impact renal or hepatic function, repeat renal and liver function tests as needed.

Question 22

If the person has missed a dose of apixaban

Answer 22

If the person has missed a dose of apixaban, the forgotten dose may be taken until half of the dosing interval has passed.
This means that the forgotten dose can be taken up until 6 hours after the scheduled intake. After this time point, the dose should be skipped and the next scheduled dose should be taken.
The 6-hour interval may be extended in people with a high stroke risk and low bleeding risk.

Question 23

If the person has taken a double dose of apixaban

Answer 23

If the person has taken a double dose of apixaban, they should omit the next planned dose (that is, after 12 hours) and resume treatment as normal 24 hours after the double dose intake.

Question 24

Dabigatran dose?
For the prophylaxis of stroke and systemic embolism in adults with non-valvular AF and with one or more risk factors, such as previous stroke or transient ischaemic attack, symptomatic heart failure, age 75 years or older, diabetes mellitus, or hypertension:
Duration?

Answer 24

150 mg twice a day.
Reduced dose of 110–150 mg BD if:
- Is aged 75–79 years.
- Moderate renal impairment [CrCl] 30–50 mL/minute),
- Is at increased risk of bleeding.
Reduced dose of 110 mg BD if:
- Is aged 80 years and older.
- Concurrent treatment with verapamil. 

Treatment is usually long term.

Question 25

Dabigatran dose?
For the treatment of DVT and PE and the prevention of recurrent DVT and PE, following initial use of parenteral anticoagulation for at least 5 days:
Duration?

Answer 25

150 mg twice a day.
Reduced dose of 110–150 mg BD if:
- Is aged 75–79 years.
- Moderate renal impairment [CrCl] 30–50 mL/minute),
- Is at increased risk of bleeding.
Reduced dose of 110 mg BD if:
- Is aged 80 years and older.
- Concurrent treatment with verapamil. 

Duration <= risk:benefit for bleeding

• Short duration (at least 3 months) = transient risk factors (eg recent surgery, trauma, immobilization).
• Longer durations = permanent risk factors or idiopathic DVT or PE.

Question 26

Dabigatran dose?

For the prevention of VTE in knee replacement surgery:

Answer 26

110 mg to be taken 1–4 hours after surgery, followed by 220 mg once daily for 10 days.
Reduced dose of 75 mg taken 1–4 hours after surgery, followed by 150 mg once daily for 10 days if:
- Is aged 75 years or older.
- Is receiving concurrent treatment with verapamil.
- Mod renal impairment (CrCl 30–50 mL/minute).

Question 27

Dabigatran dose?

For the prevention of VTE in hip replacement surgery:

Answer 27

110 mg to be taken 1–4 hours after surgery, followed by 220 mg once daily for 28–35 days.
Reduced dose of 75 mg taken 1–4 hours after surgery, followed by 150 mg once daily for 28–35 days if:
- Is aged 75 years or older.
- Is receiving concurrent treatment with verapamil.
- Mod renal impairment (CrCl 30–50 mL/minute).

Question 28

Dabigatran is contraindicated in:

Answer 28

• [CrCl] less than 30 mL/minute
• Active bleeding.
• A prosthetic heart valve
• Antiphospholipid syndrome
• Severe hepatic impairment / disease expected to have any impact on life expectancy.
• Elevated liver enzymes (if they are more than twice the upper limit of normal).
• People with significant risk of major bleeding

Question 29

Dabigatran use in caution with;

Answer 29

• Elderly (aged 75 years and older) — dose reduction
• Mod renal impairment (CrCl 30–50 mL/minute) — dose reduction (80% of dabigatran is excreted renally).
• Body weight < 50 kg — monitoring for bleeding and anaemia (low body weight may ^ plasma concentrations). No dose adjustment is needed.
• Other risk factors for bleeding, such as gastritis, gastro-oesophageal reflux, oesophagitis, recent biopsy, recent major trauma, or thrombocytopenia — close monitoring for signs of bleeding and anaemia is recommended.

Question 30

Dabigatran x verapamil

Answer 30

Verapamil — dose reduction is indicated (verapamil increases plasma concentrations of dabigatran).

Question 31

Dabigatran x nsaids

Answer 31

Other drugs that can cause bleeding, such as nonsteroidal anti-inflammatory drugs (NSAIDs) — if concurrent treatment is unavoidable, close monitoring for signs of bleeding and anaemia is recommended.

Question 32

specific reversal agent indicated in adults treated with dabigatran when rapid reversal of its anticoagulant effects is required.

Answer 32

Idarucizumab (Praxbind®)

Question 33

ADR Dabigatran

• common
• uncommon

Answer 33

Other adverse effects of dabigatran include:
Common — abnormal hepatic function.
Uncommon — anaemia, diarrhoea, hyperbilirubinaemia, nausea, post procedural/wound complications, and vomiting.

Question 34

Dabigatran
x ciclosporin
x dronedarone
x ketoconazole

Answer 34

Strong inhibitors of P-glycoprotein, such as ciclosporin, dronedarone, itraconazole, and ketoconazole — plasma conc of dabigatran is ^ by these drugs (dabigatran is a substrate for P-gp).
The manufacturer of dabigatran advises to avoid concurrent use.

Question 35

mild to moderate pgp inhibitors; amiodarone, verapamil, quinidine
x Dabigatran

Answer 35

Mild to moderate P-gp inhibitors, such as amiodarone, verapamil, and quinidine — plasma concentration of dabigatran is ^ by these drugs.
Verapamil: reduce to 110 mg BD + monitor for signs of bleeding.
Amiodarone / Quinidine: manufacturer of dabigatran advises that no dose adjustment is necessary but the person should be monitored closely for signs of bleeding or anaemia.

Question 36

enzyme inducers x dabigatran

Answer 36

Strong inducers of P-gp, such as carbamazepine, phenytoin, rifampicin, and St John’s Wort — plasma concentration of dabigatran is reduced by these drugs.
The manufacturer of dabigatran advises to avoid concurrent use with these drugs.

Question 37

Dabigatran
x SSRI
x SNRI
x venlafaxine

Answer 37

SSRI (such as citalopram)
SNRI (duloxetine)
Venlafaxine
— possible ^ risk of bleeding with dabigatran
- Manufacturer advises to avoid concurrent use.
If concurrent use is indicated, monitor closely for signs of bleeding or anaemia.

Question 38

Switching from warfarin to dabigatran:

Answer 38

Stop warfarin, and measure INR:
INR < 2, start dabigatran.
INR 2 - 2.5, start dabigatran the next day.
INR > 2.5, wait until INR < 2 before starting dabigatran.
The time taken for the person’s INR to reach less than 2 will vary from person to person and will depend on what the person’s initial INR level was.

Question 39

Switching from dabigatran to warfarin:

Answer 39

Start warfarin, but do not stop dabigatran.
After dual tx for 2 days measure INR before next Dabigatran dose:
- Within target range: STOP dabigatran and continue with warfarin.
- NOT in range: continue BOTH until INR in range, then stop dabigatran. Warfarin has a slow onset of action and may take 5–10 days before the INR is within range.
After tx with dabigatran has stopped:
Measure the INR after 24 hours.
Monitor INR closely (eg once a week) in the first month of warfarin tx until three consecutive stable INR values (for example between 2–3).

Question 40

Switching from dabigatran to another direct-acting oral anticoagulant (DOAC):
vice versa?

Answer 40

Stop dabigatran, and start the new DOAC (apixaban, edoxaban, or rivaroxaban) when the next dose of dabigatran is due.
and vice versa.

Question 41

Dabigatran

- minor surgery/bleeding risk?

Answer 41

Recommended not to interrupt oral anticoagulation.
Procedures can be performed 12–24 hours after the last dose of dabigatran is taken.
It may be practical to have the intervention scheduled 18–24 hours after the last dose of dabigatran is taken, then restart dabigatran 6 hours later. This means that one dose of dabigatran may be missed.

Question 42

Dabigatran

• low bleeding risk
• high bleeding risk

Answer 42

Low bleeding risk, dabigatran should be stopped at least 24 hours before the procedure.
- (CrCl) is 50–79 mL/minute, dabigatran should be stopped at least 36 hours before the procedure.
- CrCl is 30–49 mL/minute, dabigatran should be stopped at least 48 hours before the procedure.
HIGH bleeding risk, dabigatran should be stopped at least 48 hours before the procedure.
- CrCl is 50–79 mL/minute, dabigatran should be stopped at least 72 hours before the procedure.
- CrCl is 30–49 mL/minute, dabigatran should be stopped at least 96 hours before the procedure.

Question 43

Dabigatran monitoring

• start of tx
• stable tx

Answer 43

START
- baseline clotting screen, RFT. LFT, FBC
Once tx started, review regularly, preferably after 1 month initially and at least every 3 months thereafter. Follow-up intervals may be longer (up to every 6 months) or shorter (every month) depending on patient factors, such as renal function, age, and comorbidities.

Question 44

Edoxaban
For the prevention of stroke and systemic embolism in non-valvular AF in people with at least one risk factor, such as congestive heart failure, HTN, aged 75 years and over, DB, previous stroke or transient ischaemic attack:
The recommended dose is _

Answer 44

For the prevention of stroke and systemic embolism in non-valvular AF with at least 1 risk factor:
60 mg once daily.
Reduced dose 30 mg OD:
- Weighs 60 kg or less.
- Mod or severe renal impairment ([CrCl] 15–50 mL/minute).
- Concurrent tx with any of the following P-glycoprotein (P-gp) inhibitors: ciclosporin, dronedarone, erythromycin, or ketoconazole.

Question 45

Edoxaban

For the treatment of deep vein thrombosis (DVT) and pulmonary embolism (PE), and the prevention of recurrent DVT and PE:

Answer 45

60 mg OD
reduced 30 mg OD if <60kg / mod-sev CrCl 25-50 or concurrent tx with PGP inhibitors; ciclosporin, dronedarone, erythromycin or ketoconazole
Short duration of treatment (at least 3 months) should be based on transient risk factors (for example, recent surgery, trauma, immobilization), and longer durations should be based on permanent risk factors.

Question 46

Rivaroxaban
For the prophylaxis of stroke and systemic embolism in adults with non-valvular atrial fibrillation and at least one risk factor, such as congestive heart failure, hypertension, previous stroke or transient ischaemic attack, age 75 years or older, or diabetes mellitus:

Answer 46

20 mg once daily.
IF mod-severe renal impairment ([CrCl] 15–49 mL/minute), dose is 15 mg once daily.
For this indication, treatment with rivaroxaban is usually long term.

Question 47

Rivaroxaban

For the treatment of deep vein thrombosis (DVT) and pulmonary embolism (PE):

Answer 47

15 mg BD for first 21 days, then 20 mg OD thereafter.
IF mod - sev renal impairment (CrCl 15–49 mL/minute), following the first 21 days of treatment for DVT or PE:
dose reduction 15 mg OD should be considered if risk of bleeding > risk of recurrent DVT or PE.

Short-term tx (3 months) for people with transient risk factors, e.g. recent surgery and trauma.
Long-term tx for permanent risk factors or idiopathic (unprovoked) DVT or PE.

Question 48

Rivaroxaban
For the prophylaxis of recurrent DVT and PE in adults (following completion of at least 6 months of anticoagulant treatment):

Answer 48

10 mg OD, increasing to 20 mg OD in high risk people (complicated comorbidities / previous recurrence with rivaroxaban 10 mg OD).
IF mod - sev renal impairment (CrCl 15–49 mL/minute):
- Reduce 20mg OD dose to 15mg OD
risk bleeding > risk of recurrent DVT / PE
- Dose 10mg OD stays 10mg OD

Question 49

Rivaroxaban

For the prophylaxis of VTE for hip replacement surgery:

Answer 49

10 mg once daily for 35 days, to be started 6–10 hours after surgery.

Question 50

Rivaroxaban

For the prophylaxis of VTE for knee replacement surgery:

Answer 50

10 mg OD for 14 days, to be started 6–10 hours after surgery.

Question 51

Rivaroxaban
For the prophylaxis of atherothrombotic events following an acute coronary syndrome with elevated cardiac biomarkers (in combination with aspirin alone or aspirin and clopidogrel):

Answer 51

The recommended dose is 2.5 mg BD.

The usual duration is 12 months.

Question 52

Rivaroxaban
For the prophylaxis of atherothrombotic events in adults with coronary artery disease or symptomatic peripheral artery disease at high risk of ischaemic events (in combination with aspirin):

Answer 52

The recommended dose is 2.5 mg twice daily.

Question 53

Baseline prothrombin measurements should be taken before starting treatment with \_\_\_.
A. Edoxaban
B. Apixaban
C. Rivaroxaban
D. Warfarin

Answer 53

Baseline prothrombin measurements should be taken before starting treatment with warfarin.

Question 54

Warfarin colour boxes
0.5mg
1mg
3mg
5mg

Answer 54

0.5mg – white tablet.
1mg – brown tablet.
3mg – blue tablet.
5mg – pink tablet

Question 55

The typical induction dose of warfarin is ______

Answer 55

The typical induction dose of warfarin is 10 mg daily for 2 days, = should be tailored to individual. 
Low dose (5 mg) is more suitable for frail or elderly, low body weight, liver disease or cardiac failure, and people at ^ risk of bleeding. 
Subsequent doses depend on the prothrombin time, reported as an international normalized ratio (INR).

Question 56

The daily maintenance dose of warfarin is usually _______ mg, taken at _______ each day.

Answer 56

The daily maintenance dose of warfarin is usually 3–9 mg, taken at the same time each day.

Question 57

Where an immediate effect is required (for example in deep venous thrombosis or a pulmonary embolism), _____ or a ____________ is given concurrently — this is done in secondary care.

• heparin
• lmwh
• rivaroxaban
• warfarin
• edoxaban
• apixaban

Answer 57

Where an immediate effect is required (for example in deep venous thrombosis or a pulmonary embolism), heparin or a low molecular weight heparin is given concurrently — this is done in secondary care.

Question 58

Warfarin dose

AF

Answer 58

No need to achieve anticoagulation rapidly; a slow-loading regimen is safe and achieves therapeutic anticoagulation within 3–4 weeks.
Warfarin 1 mg or 2 mg daily is acceptable starting dose.
Avg daily maintenance dose is usually 5 mg daily; however, there is wide variation, and the daily dose may be between 1–15 mg for some people.

Question 59

What is the duration of treatment with warfarin?

For people with deep vein thrombosis (DVT) and pulmonary embolism (PE)

Answer 59

6 weeks = distal DVT (calf vein thrombosis).
3 months = proximal DVT or PE (known temporary risk factors; considered to be a low recurrence risk)
6 months = proximal DVT unknown cause (idiopathic).
Long term if there have been recurrent DVTs or PEs.
Warfarin can be stopped abruptly without harm when the duration of treatment is completed.

Question 60

Warfarin

For people with atrial fibrillation (AF):

Answer 60

Long term.
If going to have cardioversion, the target INR should be achieved at least 3 weeks before cardioversion and 4 weeks after (if normal sinus rhythm is maintained).

People undergone cardioversion and have a high risk of AF recurring also require long-term warfarin. People at high risk of AF recurring include those with:

• A history of failed attempts at cardioversion.
• Structural heart disease (mitral valve disease, left ventricular dysfunction, or an enlarged left atrium).
• A prolonged history of AF (greater than 12 months).
• Previous recurrences of AF.

Question 61

For people with mechanical prosthetic heart valves, warfarin treatment is usually ___ term.

Answer 61

For people with mechanical prosthetic heart valves, warfarin treatment is usually long term.

Question 62

Warfarin contraindicated in

Answer 62

Warfarin is contraindicated:

• Haemorrhagic stroke.
• Clinically significant bleeding.
• Severe hepatic impairment.
• Within 72 hours of major surgery with risk of severe bleeding.
• Within 48 hours postpartum.
• In pregnant women — risk of teratogenicity.
• In people taking drugs where interactions lead to a significantly increased risk of bleeding.

Question 63

The following factors may exaggerate the effect of warfarin and necessitate a dose reduction:

Answer 63

Weight loss.
Acute illness
Smoking cessation.

Question 64

The following factors may reduce the effect of warfarin and necessitate a dose increase:

Answer 64

Weight gain.
Diarrhoea.
Vomiting.

Question 65

is indicated as an antidote to coumarin anticoagulants (such as warfarin) in the treatment of haemorrhage or threatened haemorrhage, associated with a low blood level of prothrombin or factor VII.

Answer 65

Vitamin K1 phytomenandione

Question 66

Other adverse effects of warfarin include:
Rare or very rare —
Frequency unknown —
Serious ADR —

Answer 66

Other adverse effects of warfarin include:
Rare or very rare — alopecia, nausea, and vomiting.
Frequency unknown — blue toe syndrome, diarrhoea, fever, haemothorax, jaundice, pancreatitis, skin reactions, and abnormal hepatic function.

• Skin necrosis and calciphylaxis are rare but serious adverse effects of warfarin.
  Warfarin-related skin necrosis presents as painful, localized skin lesions (due to thrombosis of venules and capillaries) within subcutaneous fat. => STOP warfarin
  More likely in ppl with acute heparin-induced thrombocytopenia (HIT) /pre-existing congenital protein C or protein S deficiency.
  The lesions can occur in areas of fatty tissue, such as the breasts, abdomen, or in the extremities.
• Calciphylaxis is a rare syndrome of vascular calcification with cutaneous necrosis, associated with high mortality. Mainly in people with end-stage renal disease on dialysis or in people with known risk factors, such as protein C or S deficiency, hyperphosphataemia, hypercalcaemia, or hypoalbuminaemia.
  Advise people taking warfarin to seek urgent medical advice if they develop a painful skin rash.
  If diagnosed, appropriate treatment should be started and stopping warfarin treatment considered.

Question 67

If prescribing a drug that may interact, what should you do to monitor Warfarin /effects?

Answer 67

If prescribing a drug that may interact, check the person’s international normalized ratio (INR) 3–5 days after starting treatment with the new drug.