2026 ICD-10-CM Diagnosis Code T46.1X4APoisoning by calcium-channel blockers, undetermined, initial encounter
T46.1X4A is a billable ICD-10-CM diagnosis code for poisoning by calcium-channel blockers, undetermined, 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. In AHRQ's Clinical Classifications Software (CCSR), this diagnosis falls under External cause codes: intent of injury, undetermined; External cause codes: poisoning by drug; and Poisoning by drugs, initial encounter.
Code Identity
Code Classification
Coding GuidelinesGuidance
When coding a poisoning or reaction to the improper use of a medication (e.g., overdose, wrong substance given or taken in error, wrong route of administration), first assign the appropriate code from categories T36-T50. The poisoning codes have an associated intent as their 5th or 6th character (accidental, intentional self-harm, assault and undetermined). If the intent of the poisoning is unknown or unspecified, code the intent as accidental intent. The undetermined intent is only for use if the documentation in the record specifies that the intent cannot be determined. Use additional code(s) for all manifestations of poisonings.
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
Bepridil
a long-acting calcium-blocking agent with significant anti-anginal activity. the drug produces significant coronary vasodilation and modest peripheral effects. it has antihypertensive and selective anti-arrhythmia activities and acts as a calmodulin antagonist.Diltiazem
a benzothiazepine derivative with vasodilating action due to its antagonism of the actions of calcium ion on membrane functions.Felodipine
a dihydropyridine calcium antagonist with positive inotropic effects. it lowers blood pressure by reducing peripheral vascular resistance through a highly selective action on smooth muscle in arteriolar resistance vessels.Fendiline
coronary vasodilator; inhibits calcium function in muscle cells in excitation-contraction coupling; proposed as antiarrhythmic and antianginal agents.Gallopamil
coronary vasodilator that is an analog of iproveratril (verapamil) with one more methoxy group on the benzene ring.Isradipine
a potent antagonist of calcium channels that is highly selective for vascular smooth muscle. it is effective in the treatment of chronic stable angina pectoris, hypertension, and congestive cardiac failure.Lidoflazine
coronary vasodilator with some antiarrhythmic action.Nicardipine
a potent calcium channel blockader with marked vasodilator action. it has antihypertensive properties and is effective in the treatment of angina and coronary spasms without showing cardiodepressant effects. it has also been used in the treatment of asthma and enhances the action of specific antineoplastic agents.Nifedipine
a potent vasodilator agent with calcium antagonistic action. it is a useful anti-anginal agent that also lowers blood pressure.Nimodipine
a calcium channel blockader with preferential cerebrovascular activity. it has marked cerebrovascular dilating effects and lowers blood pressure.Nisoldipine
a dihydropyridine calcium channel antagonist that acts as a potent arterial vasodilator and antihypertensive agent. it is also effective in patients with cardiac failure and angina.Nitrendipine
a calcium channel blocker with marked vasodilator action. it is an effective antihypertensive agent and differs from other calcium channel blockers in that it does not reduce glomerular filtration rate and is mildly natriuretic, rather than sodium retentive.Verapamil
a calcium channel blocker that is a class iv anti-arrhythmia 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
Poisoning
A poison is any substance that is harmful to your body. You might swallow it, inhale it, inject it, or absorb it through your skin. Any substance can be poisonous if too much is taken. Poisons can include:
Read the full article at MedlinePlus
Courtesy of MedlinePlus, a service of the U.S. National Library of Medicine.
Convert T46.1X4A to ICD-9-CMHistory
The closest ICD-9-CM equivalents under the General Equivalence Mappings.
Code HistoryHistory
Questions About T46.1X4AOverview
Is T46.1X4A (Poisoning by calcium-channel blockers, undetermined) a billable code?
Yes. This is a billable ICD-10-CM code, specific enough to report poisoning by calcium-channel blockers, undetermined, initial encounter on HIPAA-covered claims from October 1, 2025 through September 30, 2026.
What does the 7th character A in T46.1X4A mean?
The final character A marks the initial encounter: use it while the patient is receiving active treatment for poisoning by calcium-channel blockers, undetermined, such as an emergency visit or first evaluation.
What MS-DRG does T46.1X4A group to?
When poisoning by calcium-channel blockers, undetermined, initial encounter is the principal diagnosis on an inpatient stay, it groups to MS-DRG 917, 918, with relative weights from 0.8571 to 1.5684 depending on complications. Higher weights mean higher Medicare reimbursement.
What is the ICD-9 equivalent of T46.1X4A?
Under the General Equivalence Mappings, poisoning by calcium-channel blockers, undetermined, initial encounter converts to ICD-9-CM 972.9 (pois-cardiovasc agt NEC) and E980.4 (undet pois-med agnt NEC). 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.
