# 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?

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> language: en  
> subject: Adverse Effects/Contraindications/Interactions  
> category: PPT

## Question

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?

## Option

1. Administer both medications because they act on different diseases.
2. Give both medications and obtain a complete blood count next month.
3. Hold only allopurinol because it always causes an immediate allergic reaction.
4. Hold the affected medications and clarify the regimen because allopurinol requires a major azathioprine dose reduction. **✔ Correct answer**

**Correct answer: 4**

## 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.

## In-depth explanation

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

## Clinical scenario

Interaction review
Verify the azathioprine dose, allopurinol indication, blood-count plan, and authorized dose adjustment before coadministration.

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