Oral anticoagulants

Developed in collaboration with CASA Medical.

This clinical practice guideline is focussed on warfarin and the Direct-acting Oral Anti Coagulants (DOACs). This CPG does not apply to injected anticoagulants such as heparin products.  

Warfarin (Coumardin, Marevan) is a medication that acts on the Vitamin K pathways for clotting. DOACs are a newer class of oral medications that act on other blood clotting pathways. They are used as an anticoagulant for the treatment and prevention of venous thromboembolic (VTE) disease. 

DOACs are commonly used in DVT, PE, non-valvular atrial fibrillation (AF) and other conditions associated with increased risk of blood clots. Warfarin is still used in valvular AF, patients with impaired renal function, and in situations where DOACs are ineffective or otherwise can’t be used.  

Due to significant interactions with both diet and other drugs, warfarin requires frequent monitoring using the international normalised ratio (INR) to ensure that it remains within its therapeutic range. There is no routinely available testing for DOAC effectiveness, so if compliance is measured it is by monitoring dispensing or GP records. 

As warfarin and DOACs have increased risk of bleeding and the conditions being treated are of aeromedical significance, all pilots requiring anticoagulation needed to be assessed by the regulator. 

Warfarin and Novel Oral Anticoagulants (NOACs) may be approved for use by pilots and controllers, subject to assessment of the underlying medical condition. Holders of Class 1 and Class 3 medical certificates using anticoagulation medication will be subject to multi-crew and/or proximity restrictions. The issue of a Class 2 medical certificate without safety pilot restriction may be approved subject to assessment of underlying medical condition.   

Pilots or controllers considering point of care INR testing for warfarin treatment must:

• receive training and education in operating the monitor and managing warfarin dosing.
• Use a device approved by the appropriate medical regulatory authority, and
• Verify the accuracy of readings with the standard laboratory testing every 3 months.

Pilot and controller information

Stop flying or operating and inform your ME if:

• On commencement of anticoagulant treatment
• Any bleeding complications of treatment (significant bruising, nosebleeds, blood in any body fluids)
• Symptomatic recurrence of the condition being treated
• If on warfarin INR is outside the safe range (≥ 1.8 and ≤ 3.5)
• If a point of care device records a reading outside the safety range, this needs to be verified with formal laboratory INR
• Commencement of other medications that may interfere with anticoagulant activity.

Aeromedical implications

Effect of aviation on treatment

• Variable control due to potential impacts from occupational demands of:
  • shift work, long-haul and time zone changes causing missed or delayed doses
• For warfarin: irregular food intake and/or or changes in diet that can affect the INR due to varying vitamin K levels within different foods (e.g., green leafy vegetables are high in vitamin K).

Effect of treatment on aviation

• Subtle incapacitation/distraction from minor persistent bleeding
• Reduced survivability / tolerance for trauma (for example due to turbulence or other emergencies)
• Overt incapacitation:
  • From severe bleeding or pain (eg. cerebrovascular or gastrointestinal bleeding)
  • Loss of consciousness from cerebrovascular bleed
  • Sudden death from massive haemorrhage

Approach to medical certification

Based on the condition

• Risk associated with the underlying condition necessitating anticoagulation must also be considered

Demonstrated stability

• Compliance with treatment protocol  
• Minimum of four weeks of observation
• For warfarin: the last four INRs at least one week apart must be within the safety target range.
• No clinically significant bleeding events

Risk assessment protocol - information required

Cumulative risk assessment performed by ME includes:

• risks associated with the medication
  risks due to the condition for which anticoagulation is indicated
  additive risks due to other co-morbid conditions.

A report from the treating doctor with the following information will be required:

• For warfarin:
  • Confirm that the INR therapeutic target range matches the INR safety range
  • The serial INRs have been reviewed
  • A minimum of four weeks of observation is required, and last four INRs at least one week apart must be within the therapeutic target range.
• Bleeding prediction risk, such as HAS-BLED sore with comment from the treating doctor on whether modifiable risk factors are adequately managed.
• Monitoring regime including compliance with and stability of anticoagulant medication.
• Control of comorbidities that increase risk of bleeding such as liver disease, heart failure, renal disease, hypertension, diabetes.
  • Copy of eGFR result must be provided with DOAC treatment
• Any side-effects, including any clinically significant bleeding.
• Follow-up plan for review of treatment and of the underlying condition. 

ME aeromedical decision guide

If ALL the following criteria are met MEs may issue the pilot or controller a medical certificate. MEs are to forward all the documentation for the assessment to CAA.

ME must confirm	Tick
Not a new diagnosis of VTE or other disorder associated with increased VTE/ stroke risk
Treating specialist/GP reports indicates underlying condition and its treatment are stable on current management and no changes recommended
No evidence of recurrence of VTE or new stroke event
Symptoms of treated condition are stable and well-controlled
If on DOAC evidence of compliance of use
If on Warfarin: No concerns with interactions eg St John’s Wort, Alcohol, Current antibiotic use
No coagulation disorders Eg PT, PTT, Protein S and C, Factor V Leiden
ME considers safe to certify

An AMC referral to CAA Aviation Medicine teams is required if the pilot’s or controller’s condition does not meet all the above criteria and they consent to their condition being considered under flexibility to the CAR 67 rules.  

Recommended conditions on medical certificate

• For a Class 1 certificate and the pilot is taking anticoagulants, a “Not valid for single pilot air operations carrying passengers” restriction is imposed.
• For pilots or controllers on warfarin - 80% INRs must be in the ≥ 1.8 and ≤ 3.5 range

ME letters

Anticoagulation medical certificate letter [DOCX 22 KB]

Anticoagulation 020 operational restrictions letter [DOCX 28 KB]