2026 ICD-10-CM Diagnosis Code T46.3X6AUnderdosing of coronary vasodilators, initial encounter
T46.3X6A is a billable ICD-10-CM diagnosis code for underdosing of coronary vasodilators, 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). 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 Underdosing of drugs and medicaments, initial encounter.
Code Identity
Code Classification
Code EditsBilling
Medicare Code Editor checks that affect claim validity for T46.3X6A.
Coding GuidelinesGuidance
Underdosing refers to taking less of a medication than is prescribed by a provider or a manufacturer's instruction. Codes for underdosing should never be assigned as principal or first-listed codes. If a patient has a relapse or exacerbation of the medical condition for which the drug is prescribed because of the reduction in dose, then the medical condition itself should be coded.
The appropriate 7th character is to be added to each code from block Poisoning by, adverse effect of and underdosing of agents primarily affecting the cardiovascular system (T46). 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
Chromonar
a coronary vasodilator agent.Dilazep
coronary vasodilator with some antiarrhythmic activity.Aspirin, Dipyridamole Drug Combination
a drug combination of aspirin and dipyridamole that functions as a platelet aggregation inhibitor, used to prevent thrombosis and stroke in transient ischemic attack patients.Dipyridamole
a phosphodiesterase inhibitor that blocks uptake and metabolism of adenosine by erythrocytes and vascular endothelial cells. dipyridamole also potentiates the antiaggregating action of prostacyclin. (from ama drug evaluations annual, 1994, p752)Erythrityl Tetranitrate
a vasodilator with general properties similar to nitroglycerin. (from martindale, the extra pharmacopoeia, 30th ed, p1020)Heptaminol
an amino alcohol that has been used as a myocardial stimulant and vasodilator and to relieve bronchospasm. its most common therapeutic use is in orthostatic hypotension. the mechanism of heptaminol's therapeutic actions is not well understood although it has been suggested to affect catecholamine release or calcium metabolism.Hexobendine
a potent vasoactive agent that dilates cerebral and coronary arteries, but slightly constricts femoral arteries, without any effects on heart rate, blood pressure or cardiac output.Isosorbide Dinitrate
a vasodilator used in the treatment of angina pectoris. its actions are similar to nitroglycerin but with a slower onset of action.Khellin
a vasodilator that also has bronchodilatory action. it has been employed in the treatment of angina pectoris, in the treatment of asthma, and in conjunction with ultraviolet light a, has been tried in the treatment of vitiligo. (from martindale, the extra pharmacopoeia, 30th ed, p1024)Molsidomine
a morpholinyl sydnone imine ethyl ester, having a nitrogen in place of the keto oxygen. it acts as nitric oxide donors and is a vasodilator that has been used in angina pectoris.Nicorandil
a derivative of the niacinamide that is structurally combined with an organic nitrate. it is a potassium-channel opener that causes vasodilatation of arterioles and large coronary arteries. its nitrate-like properties produce venous vasodilation through stimulation of guanylate cyclase.Oxyfedrine
a drug used in the treatment of angina pectoris, heart failure, conduction defects, and myocardial infarction. it is a partial agonist at beta adrenergic receptors and acts as a coronary vasodilator and cardiotonic agent.Prenylamine
a drug formerly used in the treatment of angina pectoris but superseded by less hazardous drugs. prenylamine depletes myocardial catecholamine stores and has some calcium channel blocking activity. (from martindale, the extra pharmacopoeia, 30th ed, p1406)Trapidil
a coronary vasodilator agent.
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
Medication Errors
Medicines treat infectious diseases, prevent problems from chronic diseases, and ease pain. But medicines can also cause harmful reactions if not used correctly. Errors can happen in the hospital, at the health care provider's office, at the pharmacy, or at home. You can help prevent errors by:
Read the full article at MedlinePlus
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Convert T46.3X6A to ICD-9-CMHistory
Code HistoryHistory
Questions About T46.3X6AOverview
Is T46.3X6A (Underdosing of coronary vasodilators) a billable code?
Yes. This is a billable ICD-10-CM code, specific enough to report underdosing of coronary vasodilators, initial encounter on HIPAA-covered claims from October 1, 2025 through September 30, 2026.
What does the 7th character A in T46.3X6A mean?
The final character A marks the initial encounter: use it while the patient is receiving active treatment for underdosing of coronary vasodilators, such as an emergency visit or first evaluation.
Can T46.3X6A be a principal diagnosis?
No. The Medicare Code Editor rejects this code as a principal diagnosis because underdosing of coronary vasodilators, initial encounter describes a circumstance that influences health status rather than a current illness. Report it as a secondary diagnosis.
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.
