2026 ICD-10-CM Diagnosis Code T45.525AAdverse effect of antithrombotic drugs, initial encounter
T45.525A is a billable ICD-10-CM diagnosis code for adverse effect of antithrombotic drugs, 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. Coders also document this condition as a series prostaglandin adverse reaction. 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 T45.525A.
Approximate SynonymsGuidance
Alternate terms and clinical phrases that map to this code.
- A series prostaglandin adverse reaction
- Adverse reaction to clopidogrel
- Adverse reaction to platelet aggregation inhibitor
- Duodenal ulcer caused by drug
- Duodenal ulcer induced by platelet aggregation inhibitor
- Epoprostenol adverse reaction
- Gastric ulcer caused by drug
- Gastric ulcer induced by platelet aggregation inhibitor
- I series prostaglandin adverse reaction
- Prostaglandin 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 primarily systemic and hematological agents, not elsewhere classified (T45). 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
Epoprostenol
a prostaglandin that is a powerful vasodilator and inhibits platelet aggregation. it is biosynthesized enzymatically from prostaglandin endoperoxides in human vascular tissue. the sodium salt has been also used to treat primary pulmonary hypertension (hypertension, pulmonary).Receptors, Epoprostenol
cell surface receptors for epoprostenol. they are coupled to heterotrimeric g-proteins.Ticlopidine
an effective inhibitor of platelet aggregation commonly used in the placement of stents in coronary arteries.
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.
| Substance | Accidental | Self-harm | Assault | Undetermined | Adverse Effect | Underdosing |
|---|---|---|---|---|---|---|
| Antithrombotic | T45.521 | T45.522 | T45.523 | T45.524 | T45.525 | T45.526 |
| Epoprostenol | T45.521 | T45.522 | T45.523 | T45.524 | T45.525 | T45.526 |
| Indobufen | T45.521 | T45.522 | T45.523 | T45.524 | T45.525 | T45.526 |
| Prostacyclin | T45.521 | T45.522 | T45.523 | T45.524 | T45.525 | T45.526 |
| Prostaglandin (I2) | T45.521 | T45.522 | T45.523 | T45.524 | T45.525 | T45.526 |
| Prostaglandin (I2)::E1 | T45.521 | T45.522 | T45.523 | T45.524 | T45.525 | T45.526 |
| Prostaglandin (I2)::E2 | T45.521 | T45.522 | T45.523 | T45.524 | T45.525 | T45.526 |
| Prostaglandin (I2)::F2 alpha | T45.521 | T45.522 | T45.523 | T45.524 | T45.525 | T45.526 |
| Ticlopidine | T45.521 | T45.522 | T45.523 | T45.524 | T45.525 | T45.526 |
| Triflusal | T45.521 | T45.522 | T45.523 | T45.524 | T45.525 | T45.526 |
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 T45.525A to ICD-9-CMHistory
The closest ICD-9-CM equivalents under the General Equivalence Mappings.
Code HistoryHistory
Questions About T45.525AOverview
Is T45.525A (Adverse effect of antithrombotic drugs) a billable code?
Yes. This is a billable ICD-10-CM code, specific enough to report adverse effect of antithrombotic drugs, initial encounter on HIPAA-covered claims from October 1, 2025 through September 30, 2026.
What does the 7th character A in T45.525A mean?
The final character A marks the initial encounter: use it while the patient is receiving active treatment for adverse effect of antithrombotic drugs, such as an emergency visit or first evaluation.
What MS-DRG does T45.525A group to?
On inpatient claims, adverse effect of antithrombotic drugs, 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 T45.525A be a principal diagnosis?
No. The Medicare Code Editor rejects this code as a principal diagnosis because adverse effect of antithrombotic drugs, 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 T45.525A?
Under the General Equivalence Mappings, adverse effect of antithrombotic drugs, initial encounter converts to ICD-9-CM 995.29 (adv eff med/biol NEC/NOS) and E934.2 (adv eff anticoagulants). 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.
