Tailoring treatment: interacting medicines

Last updated: Sunday, June 13, 2021

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It’s the last day of your medicines information rotation and you receive an urgent call from the pharmacist covering the orthopaedic unit. She is trying to establish if there is an interaction between rifampicin and apixaban. Upon questioning you find out that the patient usually takes apixaban for atrial fibrillation. He was switched to enoxaparin after surgery on his knee for osteomyelitis. He has been taking rifampicin postoperatively as per the hospital guidelines and requires a further 6 weeks’ treatment. The team would like to discharge him today and so want to restart his apixaban.

It quickly becomes apparent that apixaban and all the direct oral anticoagulants interact unpredictably and significantly with rifampicin. Warfarin interacts with rifampicin too, but the patient’s INR could be monitored and the dose adjusted accordingly. Enoxaparin at home might be an option while the patient is taking rifampicin, and then swapping back to apixaban when the antibiotic course is complete. A further solution might be to use a different antibiotic depending upon the sensitivities of the causative bacteria.

You present all these options to your colleague and discuss the relative merits and disadvantages for the individual patient concerned, taking into account the support he has at home managing his medicines. She takes these potential solutions to the medical team and rings you back an hour later to let you know that they have changed the antibiotic to clindamycin and restarted the apixaban. You document this outcome as evidence of your impact, and for the next time this scenario occurs.