Z16.31
Resistance to antiparasitic drug(s)
Z16.31 (also written Z1631) is a billable ICD-10-CM diagnosis code for resistance to antiparasitic drug(s). It is part of the FY2027 code set, effective October 1, 2026. It is one of the 19 codes in category Z16 (Resistance to antimicrobial drugs). The Alphabetic Index lists it under 2 entries. Its coding notes include a Code first instruction and 4 Excludes1 entries.
Guidelines tip
From the FY2027 Official Guidelines. ICD10Ref adds no rules of its own.
A Z16 code follows the infection code only if the infection code does not itself identify drug resistance.
Code first
If the underlying condition listed here is present and known, sequence it first.
- the infection
Excludes1
Not coded here. The listed conditions generally should not be reported together.
Care settings
How CMS programs treat this code. These are CMS claim edits and list entries, not coverage or eligibility rules.
Hospice: not accepted as primary
Not accepted as the principal diagnosis on a hospice claim (bill types 081x and 082x). The Integrated OCE returns an edit for this code.
Reason: Supplementary or additional code, not allowed as principal diagnosis.
Hospital CC
Counts as a complication or comorbidity (CC) when reported as a secondary diagnosis on an inpatient claim. No principal diagnosis cancels it. Some MS-DRGs also ignore a CC or MCC that defines the DRG.
Source: CMS MS-DRG Definitions Manual v44, effective October 1, 2026, Appendix CInclusion terms
Conditions classified to this code.
- Resistance to quinine and related compounds
Notes
- The codes in this category are provided for use as additional codes to identify the resistance and non-responsiveness of a condition to antimicrobial drugs.
Also from chapter/block level (3 notes)
- Z codes represent reasons for encounters. A corresponding procedure code must accompany a Z code if a procedure is performed. Categories Z00-Z99 are provided for occasions when circumstances other than a disease, injury or external cause classifiable to categories A00-Y89 are recorded as 'diagnoses' or 'problems'. This can arise in two main ways:
- (a) When a person who may or may not be sick encounters the health services for some specific purpose, such as to receive limited care or service for a current condition, to donate an organ or tissue, to receive prophylactic vaccination (immunization), or to discuss a problem which is in itself not a disease or injury.
- (b) When some circumstance or problem is present which influences the person's health status but is not in itself a current illness or injury.
Alphabetic Index terms
Terms the official Alphabetic Index lists for this code. 2 entries