The Drive-Through Warfarin Patient and Eleven Overrides
A 78-year-old woman with atrial fibrillation on warfarin 5 mg daily (INR 2.6 last week) comes through the drive-through to pick up a new prescription for sulfamethoxazole/trimethoprim DS twice daily for 7 days, written by an urgent care clinic that has no record of her medication list. Your system flags a major warfarin–TMP-SMX interaction (rising INR, bleeding risk), and because the store has cycled through three pharmacists this month, that alert has been overridden 11 times in the last 30 days. The patient is hard of hearing, declines counseling ("I've taken these before"), mentions she "takes an extra warfarin when she feels fluttery," and has visible bruising on both forearms. She is in the drive-through lane and there are five cars behind her.
1. What does drug utilization review require at this moment, and does the override history change anything?
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DUR is a pharmacist function, not a software function. Prospective review must be performed by the pharmacist before dispensing. An alert that is clicked through by a technician, or auto-overridden by a rule, is not review - it is a record of a decision nobody made.
What the review must actually resolve here:
- The interaction is real and clinically significant: TMP-SMX inhibits CYP2C9 and displaces warfarin from protein binding, so INR can climb within a few days of starting the course. Age 78 is an independent bleeding risk.
- Self-directed "extra warfarin" plus visible bruising is evidence the patient may already be over-anticoagulated.
- The prescriber has no medication list, so nobody upstream has done this work.
The override history absolutely matters. Eleven overrides of the same alert in 30 days in one store is not eleven clinical judgments; it is one workflow failure repeated, and it is exactly what a board investigator or a plaintiff's expert will pull. It also means the alert's usefulness has been destroyed by alert fatigue - which is a system problem you must fix (retier the alert, require pharmacist credentials for this override, add a hard-stop prompt).
Do not dispense silently. Either resolve the interaction and document the resolution, or hold the prescription and speak to the prescriber - this is not an alert that gets clicked past in a drive-through lane.
2. She declines counseling. What may you accept, what must you still do, and how is it documented?
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You may accept a refusal - but only a refusal of an offer that was actually made and actually meaningful. Connecticut requires that counseling be offered to every patient (or caregiver) and that the refusal be documented. A refusal does not erase the DUR obligation, and it does not erase the pharmacist's duty to intervene when the pharmacist knows of a serious, imminent risk.
Make the offer real despite the barriers:
- Drive-through + hearing impairment means "do you have any questions?" shouted through glass is not an offer. Pull the car forward, step to a private window, or offer a phone consultation later that day.
- Provide written information and highlight the bleeding signs to watch for.
- Offer to speak with her daughter or caregiver with her permission (HIPAA).
Documentation: "Counseling offered at pickup; patient declined; written information provided; warfarin–TMP-SMX interaction discussed with prescriber Dr. ___ at ___; INR recommended within 3–5 days; patient advised to report bruising/black stools and to stop self-adjusting the warfarin until she speaks with her prescriber." Initial and date it.
Boundary: a counseling refusal is not consent to skip safety steps. Contacting the prescriber is your professional act, not something the patient's refusal can waive.
3. What do you do about the bruising, the extra warfarin, and the prescriber?
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Treat the bruising as a possible adverse drug event, not a counseling talking point. Unexplained bilateral forearm bruising in a 78-year-old on warfarin who self-administers extra doses is suggestive of over-anticoagulation. Ask about gum bleeding, dark stools, dark urine, headache, and any recent falls. If she has any of these, direct her to urgent evaluation now - do not let her drive home with a plan to "call Monday."
Contact the prescriber today (urgent care clinic) and:
- Provide the complete medication list including warfarin 5 mg daily, the new TMP-SMX DS, and any OTC products.
- Recommend an INR check within 2–3 days of starting TMP-SMX, sooner given the bruising, and discuss whether an alternative antibiotic is preferable.
- Report the patient's self-adjustment behavior - the prescriber needs to know it exists.
- Also notify her primary care clinician/cardiology, since the urgent care clinic owns no longitudinal record.
Other actions: reinforce one consistent dose and no self-adjustment; screen for duplicate therapy and interacting OTCs (NSAIDs, aspirin, supplements); document everything; consider an FDA MedWatch report if harm is suspected.
And fix the system: the eleven overrides are a medication-safety finding that belongs in a root-cause discussion, not just a note in this patient's file.