Clinical judgement question: withheld incantation due to unknown INR
I’m employed as a pharmacy student at a private hospital here in Australia. I had an interesting situation in hospital dispensary today and wanted to get some opinions from pharmacists/clinical staff.
Elderly patient at an external facility was newly prescribed warfarin with a target INR of 2.5–3.5. I dispensed 1 mg warfarin pending INR review. The patient was also charted simvastatin.
Problem was:
- I had no access to pathology or EMR from the external facility
- INR was unknown at the time of dispensing
- No reliable medication history available
- I could not determine whether the patient had previously been stable on simvastatin and/or warfarin
- I contacted the nurse, but they were unable to get hold of the CMO before the dispensary closed
Given the uncertainty and potential interaction, I made the decision to temporarily withhold the simvastatin pending INR clarification.
In hindsight, I’m wondering whether this was overly conservative. My reasoning was:
- Elderly patient
- Unknown anticoagulation status/baseline INR
- Inability to assess bleeding risk
- Simvastatin was non-urgent compared with anticoagulation safety
At the same time, I recognise that statin-warfarin interactions are usually managed with monitoring rather than withholding therapy, especially if the patient may already have been stable on the combination long-term.
Curious how others would have approached this situation, particularly in settings where access to records/pathology is limited.
P.s. All of this was done under the supervision of a registered pharmacist, and they supported my decision. But just curious what people think.
**Edit: typo in title, should be “Simvastatin”.. autocorrect :/