2026 ICD-10-CM Diagnosis Code T39.2X5AAdverse effect of pyrazolone derivatives, initial encounter
T39.2X5A is a billable ICD-10-CM diagnosis code for adverse effect of pyrazolone derivatives, initial encounter. The 7th character A marks it as an initial encounter code, used while the patient is receiving active treatment. It is valid on HIPAA claims for fiscal year 2026 (October 1, 2025 through September 30, 2026) and groups to MS-DRG 917 through 918. The code is not accepted as a principal diagnosis by the Medicare Code Editor. In AHRQ's Clinical Classifications Software (CCSR), this diagnosis falls under Adverse effects of drugs and medicaments, initial encounter.
Code Identity
Code Classification
Code EditsBilling
Medicare Code Editor checks that affect claim validity for T39.2X5A.
Approximate SynonymsGuidance
Alternate terms and clinical phrases that map to this code.
- Adverse reaction to aldehyde
- Adverse reaction to aminophenazone
- Adverse reaction to chloral and/or chloral derivative
- Adverse reaction to pyrazole derivative
- Azapropazone adverse reaction
- Dichloralphenazone adverse reaction
- Dipyrone adverse reaction
- Hypothyroidism caused by drug
- Hypothyroidism resulting from phenylbutazone
- Oxyphenbutazone adverse reaction
- Phenylbutazone adverse reaction
- Uricosuric agent adverse reaction
Coding GuidelinesGuidance
When coding an adverse effect of a drug that has been correctly prescribed and properly administered, assign the appropriate code for the nature of the adverse effect followed by the appropriate code for the adverse effect of the drug.
The appropriate 7th character is to be added to each code from block Poisoning by, adverse effect of and underdosing of nonopioid analgesics, antipyretics and antirheumatics (T39). Use the following options for the applicable episode of care:
- A - initial encounter
- D - subsequent encounter
- S - sequela
Source: ICD-10-CM Official Guidelines for Coding and Reporting, FY 2026, published by CMS and the National Center for Health Statistics.
Clinical ClassificationClinical
AHRQ’s CCSR groups this code into broader clinical categories.
Clinical InformationClinical
Aminopyrine
a pyrazolone with analgesic, anti-inflammatory, and antipyretic properties but has risk of agranulocytosis. a breath test with 13c-labeled aminopyrine has been used as a non-invasive measure of cytochrome p-450 metabolic activity in liver function tests.Aminopyrine N-Demethylase
a pyrazolone with analgesic, anti-inflammatory, and antipyretic properties but has risk of agranulocytosis. a breath test with 13c-labeled aminopyrine has been used as a non-invasive measure of cytochrome p-450 metabolic activity in liver function tests.Antipyrine
an analgesic and antipyretic that has been given by mouth and as ear drops. antipyrine is often used in testing the effects of other drugs or diseases on drug-metabolizing enzymes in the liver. (from martindale, the extra pharmacopoeia, 30th ed, p29)Dipyrone
a drug that has analgesic, anti-inflammatory, and antipyretic properties. it is the sodium sulfonate of aminopyrine.Feprazone
a pyrazole that has analgesic, anti-inflammatory, and antipyretic properties. it has been used in mild to moderate pain, fever, and inflammation associated with musculoskeletal and joint disorders. (from martindale, the extra pharmacopoeia, 30th ed, p15)Oxyphenbutazone
a non-steroidal anti-inflammatory drug. oxyphenbutazone eyedrops have been used abroad in the management of postoperative ocular inflammation, superficial eye injuries, and episcleritis. (from ama, drug evaluations annual, 1994, p2000) it had been used by mouth in rheumatic disorders such as ankylosing spondylitis, osteoarthritis, and rheumatoid arthritis but such use is no longer considered justified owing to the risk of severe hematological adverse effects. (from martindale, the extra pharmacopoeia, 30th ed, p27)Phenylbutazone
a butyl-diphenyl-pyrazolidinedione that has anti-inflammatory, antipyretic, and analgesic activities. it has been used in ankylosing spondylitis; rheumatoid arthritis; and reactive arthritis.
Table of Drugs and ChemicalsClinical
Substances in the Table of Drugs and Chemicals that reference this code family. Always confirm in the Tabular List before coding.
Patient EducationClinical
Drug Reactions
Most of the time, medicines make our lives better. They reduce aches and pains, fight infections, and control problems such as high blood pressure or diabetes. But medicines can also cause unwanted reactions, such as drug interactions, side effects, and allergies.
The full article covers:
- What is a drug interaction?
- What are side effects?
- What are drug allergies?
- How can I stay safe when taking medicines?
Read the full article at MedlinePlus
Courtesy of MedlinePlus, a service of the U.S. National Library of Medicine.
Convert T39.2X5A to ICD-9-CMHistory
The closest ICD-9-CM equivalents under the General Equivalence Mappings.
Code HistoryHistory
Questions About T39.2X5AOverview
Is T39.2X5A (Adverse effect of pyrazolone derivatives) a billable code?
Yes. This is a billable ICD-10-CM code, specific enough to report adverse effect of pyrazolone derivatives, initial encounter on HIPAA-covered claims from October 1, 2025 through September 30, 2026.
What does the 7th character A in T39.2X5A mean?
The final character A marks the initial encounter: use it while the patient is receiving active treatment for adverse effect of pyrazolone derivatives, such as an emergency visit or first evaluation.
What MS-DRG does T39.2X5A group to?
On inpatient claims, adverse effect of pyrazolone derivatives, initial encounter maps to MS-DRG 917, 918, with relative weights from 0.8571 to 1.5684 depending on complications. Higher weights mean higher Medicare reimbursement.
Can T39.2X5A be a principal diagnosis?
No. The Medicare Code Editor rejects this code as a principal diagnosis because adverse effect of pyrazolone derivatives, initial encounter describes a circumstance that influences health status rather than a current illness. Report it as a secondary diagnosis.
What is the ICD-9 equivalent of T39.2X5A?
Under the General Equivalence Mappings, adverse effect of pyrazolone derivatives, initial encounter converts to ICD-9-CM 995.29 (adv eff med/biol NEC/NOS) and E935.5 (adv eff pyrazole deriv). The mapping is approximate, so confirm the match fits the documentation.
Footnotes
[1] Not chronic - A diagnosis code that does not fit the criteria for chronic condition (duration, ongoing medical treatment, and limitations) is considered not chronic. Some codes designated as not chronic are acute conditions. Other diagnosis codes that indicate a possible chronic condition, but for which the duration of the illness is not specified in the code description (i.e., we do not know the condition has lasted 12 months or longer) also are considered not chronic.
