---
title: "ICD-10-CM Z79.634: Long term (current) use of… | BillingBrief"
description: "ICD-10-CM code Z79.634: Long term (current) use of topoisomerase inhibitor. Category, related codes, and the official source, in plain English."
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---

# Z79.634 Long term (current) use of topoisomerase inhibitor

ICD-10-CM · [CMS code reference](#source)

**Official ICD-10-CM description:** Long term (current) use of topoisomerase inhibitor

## Coding notes

From the ICD-10-CM FY2027 (effective October 1, 2026) tabular list. Notes on a parent code or category apply here too.

### Also covers

-   Long term (current) use of etoposide
-   Long term (current) use of irinotecan
-   Long term (current) use of topotecan

### Includes

-   long term (current) drug use for prophylactic purposes

### Excludes2

Not part of this code, but both can be coded when both are documented.

-   long term (current) use of steroids (Z79.5-)
-   long term (current) use of agents affecting estrogen receptors and estrogen levels (Z79.81-)
-   drug abuse and dependence (F11-F19)
-   drug use complicating pregnancy, childbirth, and the puerperium (O99.32-)

### Code also

A second code may be needed. Sequencing depends on the encounter.

-   any therapeutic drug level monitoring ([Z51.81](https://billingbrief.com/icd10/z51.81/))
-   any follow-up examination (Z08-[Z09](https://billingbrief.com/icd10/z09/))

## Related codes

-   [`Z79.623` Long term (current) use of mammalian target of rapamycin (mTOR) inhibitor ICD-10-CM](https://billingbrief.com/icd10/z79.623/)
-   [`Z79.624` Long term (current) use of inhibitors of nucleotide synthesis ICD-10-CM](https://billingbrief.com/icd10/z79.624/)
-   [`Z79.630` Long term (current) use of alkylating agent ICD-10-CM](https://billingbrief.com/icd10/z79.630/)
-   [`Z79.631` Long term (current) use of antimetabolite agent ICD-10-CM](https://billingbrief.com/icd10/z79.631/)
-   [`Z79.632` Long term (current) use of antitumor antibiotic ICD-10-CM](https://billingbrief.com/icd10/z79.632/)
-   [`Z79.633` Long term (current) use of mitotic inhibitor ICD-10-CM](https://billingbrief.com/icd10/z79.633/)
-   [`Z79.64` Long term (current) use of myelosuppressive agent ICD-10-CM](https://billingbrief.com/icd10/z79.64/)
-   [`Z79.69` Long term (current) use of other immunomodulators and immunosuppressants ICD-10-CM](https://billingbrief.com/icd10/z79.69/)

## Common questions

### Is Z79.634 a billable code?

Yes. Z79.634 is a billable ICD-10-CM code in the ICD-10-CM FY2027 (effective October 1, 2026) code set.

## From the source

Official description from [CMS](https://www.cms.gov/medicare/coding-billing/icd-10-codes).
ICD-10-CM FY2027 (effective October 1, 2026).

Code set

ICD-10-CM

Category

Z79 Long term (current) drug therapy

Chapter

Factors influencing health status and contact with health services

Billable

Yes

Educational reference only. Not medical, legal, or billing advice. Always check the current official code set and payer policy before you bill. [About BillingBrief and our sources](https://billingbrief.com/about/).