Substitution instrument to address shortage of COUMADIN warfarin 5mg tablets
17 Mar 2023
Warfarin is an anticoagulant used to prevent blood from excessive clotting or forming harmful clots for patients at risk of heart attack and stroke.
As the shortage of Coumadin 5mg tablets- external site is expected to continue until 31 July 2023, the TGA has made a Serious Scarcity Substitution Instrument (SSSI) Therapeutic Goods (Serious Scarcity and Substitutable Medicine) (Warfarin) Instrument 2023 (SSSI)- external site to assist patients to access their medicine from their pharmacist without delay or interruption to treatment.
The SSSI allows a pharmacist to offer the patient or their carer a lower strength of COUMADIN warfarin tablet if the 5mg tablet is unavailable without prior approval from the prescriber. The SSSI:
- declares COUMADIN warfarin sodium 5 mg tablet (AUST R: 42279) a scarce medicine
- specifies that either: can be offered as substitute medicines
- COUMADIN warfarin sodium 1 mg tablet (AUST R: 42269)
OR - COUMADIN warfarin sodium 2 mg tablet (AUST R: 14937)
- COUMADIN warfarin sodium 1 mg tablet (AUST R: 42269)
- does NOT allow a combination of 1mg an 2mg tablets to be dispensed as a substitute
- includes specific conditions that must be met to allow substitution.
The SSSI is in force from 17 March 2023 until 7 August 2023. The TGA may, however, revoke the SSSI before its end date if the serious scarcity is resolved, or safety concerns are identified.
For more information about SSSIs see Substituting scarce medicines and Serious Scarcity Substitution Instruments (SSSIs).
Information for pharmacists
The SSSI allows you to provide the patient with the specified substitutable medicine without prior approval from the prescriber so long as the permitted circumstances provided within the SSSI are met. See both the specific permitted circumstances (in Schedule 1) and general permitted circumstances (in Schedule 2) of the SSSI for warfarin- external site.
Warfarin is an important medicine, with a narrow therapeutic index. Explain to the patient the potential for the INR to change and the need for frequent monitoring.
Ensure the patient is aware of their current dose. The dose on the prescription of warfarin often will not match the dose that the patient has been advised to take, due to frequent dose changes (according to INR results).
Advise the patient that whilst there are different brands of warfarin, these have not been shown to be bioequivalent and should not be interchanged without the prescriber’s advice.
Assess the patient’s health literacy and capacity to understand the substitution. If you have determined that the patient is not suitable to receive the substitutable medicine, contact the sponsor, Viatris on 1800 314 527 to enquire about emergency stock of COUMADIN 5mg tablets.
For patients who are dispensed the substitutable medicine:
- calculate the number of tablets and ensure correct total quantity of substitutable medicine is provided
- explain to the patient/carer the differences between the products and ensure they understand the substitution. Explain that:
- a different strength of the medicine has been supplied due to the prescribed strength being unavailable
- the substitutable medicine is of the same brand and contains the same active ingredient, however, is of a different strength, and
- if the patient takes the medicine as directed by you , the patient will receive the same dose they were prescribed.
- provide written instructions to the patient to support quality use of medicines and minimise confusion and error. You can download this patient information sheet that includes images of the scarce and substitutable tablets to ensure patients are supported with clear instructions: