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Maintenance Dosing Algorithms

A Maintenance dosing algorithm is used to suggest suitable warfarin doses and review periods for patients who are stable and fully established on warfarin treatment.

They are not suitable for initiating warfarin for patients who are starting oral anticoagulation or for treating patients who are not yet sufficiently stable on treatment.

Patients should have had at least 2 in-range INR results with a seven day review period between tests to be suitable for treating with a maintenance algorithm.

Patients who are starting warfarin should be dosed using an induction protocol or be dosed manually until sufficiently stable to be transferred to a maintenance algorithm for continued treatment. (see warfarin induction and manual dosing).

Inappropriate use of a maintenance dosing algorithm could lead to significant over-dosing or under-dosing with warfarin which could cause serious injury or fatality for the patient.

INRstar offers 2 well established maintenance algorithms – Hillingdon and Coventry.

The choice of algorithm is at the discretion of the responsible clinician but it is fair to say that the vast majority of locations use the Coventry algorithm.


 Developed by consultant haematologist Dr Peter Rose and his colleagues at the South Warwickshire Hospital. It is the default dosing maintenance algorithm included in INRstar and supersedes the Hillingdon algorithm for routine use. The Coventry algorithm may only be used once the patient’s review interval is 7 days or more. Reference: BMJ 1989; Vol 299: 1207-1209.


 Developed at the Hillingdon Hospital, Middlesex, this algorithm was the first published warfarin dosing algorithm to be made available in the UK. Like the Coventry algorithm, which superseded it for routine use, it may only be used for warfarin dosing maintenance. It can be useful for the small minority of patients who's INR overreacts to even a small change in Dose. Further details on the use of this functionality are available from INRstar Technical Support. Reference: BMJ 1984; Vol 289: 422–424

Firstly in the patients record click on  and then on .

Here you will be able to view the Current Treatment Plan and underneath that Warfarin Details.

In the Warfarin Details you can view the Dosing Method.

If you wish to change the Dosing Method click the  situated underneath the Warfarin Details section to the far bottom right.

The Warfarin Details can now be edited.

Simply select the maintenance dosing algorithm you wish to change to from the Dosing Method drop down list and click  where the Edit Treatment Plan button was before.

Category: Treating Warfarin Patients
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