A client with Crohn disease takes azathioprine 150 mg daily. A new order adds allopurinol 300 mg daily without changing azathioprine. Which action should the nurse take before administration?
1Administer both medications as ordered because using them for different conditions prevents a metabolic interaction.
2Give both medications today and schedule the first complete blood count after the next monthly appointment.
3Withhold allopurinol alone, then continue the unchanged azathioprine dose while monitoring only for a skin reaction.
4Hold both medications and clarify the azathioprine dose reduction, blood-count schedule, and monitoring plan.✓ Correct answer
Explanation
Allopurinol inhibits an azathioprine inactivation pathway. The azathioprine label recommends reducing it to approximately one-third to one-fourth of the usual dose when used with allopurinol.
Quick answer Clarify the unchanged azathioprine dose before either medication is given together.
Why this is correct Allopurinol inhibits xanthine oxidase, an azathioprine inactivation pathway, which can increase active metabolite exposure and myelotoxicity. DailyMed recommends reducing azathioprine to approximately one-third to one-fourth of the usual dose with allopurinol.
Easy analogy or mental picture One drug closes an exit door for the other. If the incoming azathioprine amount stays unchanged, exposure can accumulate.
Memory hook Allopurinol added: azathioprine dose must be deliberately reduced and monitored.
NCLEX decision rule When a new drug changes the clearance of an existing immunosuppressant, do not administer an unchanged regimen until the prescriber and pharmacist reconcile the doses and monitoring plan.
Why the other choices are wrong Different indications do not prevent interactions. Waiting a month delays risk management, and allopurinol does not invariably cause an immediate allergy.
References
1DailyMed: AzathioprineAllopurinol interaction and azathioprine dose reduction
Interaction reviewVerify the azathioprine dose, allopurinol indication, blood-count plan, and authorized dose adjustment before coadministration.