2026 ICD-10-CM Diagnosis Code T43.294APoisoning by other antidepressants, undetermined, initial encounter

ICD-10-CM Codes›S00–T88›T36-T50›T43

ICD-10-CM T43.294A
CMSSource: CMS FY 2026 ICD-10-CM dataset · Effective Oct 1, 2025 – Sep 30, 2026

T43.294A is a billable ICD-10-CM diagnosis code for poisoning by other antidepressants, 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

ICD-10-CM Code
T43.294A
Billable Status
Yes — Valid for Submission
Code Describes
Poisoning by other antidepressants, undetermined, initial encounter
Short Description
Poisoning by oth antidepressants, undetermined, init encntr
Parent Code
T43.294
Poisoning by other antidepressants, undetermined

Code Classification

ChapterS00–T88Injury, poisoning and certain other consequences of external causes
SectionT36-T50Poisoning by, adverse effect of and underdosing of drugs, medicaments and biological substances
CategoryT43Poisoning by, adverse effect of and underdosing of psychotropic drugs, not elsewhere classified
This CodeT43.294APoisoning by other antidepressants, undetermined, initial encounter

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 psychotropic drugs, not elsewhere classified (T43). 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.

CCSR EXT023
External cause codes: intent of injury, undetermined
Default principal diagnosis: inpatient No · outpatient No
CCSR EXT014
External cause codes: poisoning by drug
Default principal diagnosis: inpatient No · outpatient No
CCSR INJ022
Poisoning by drugs, initial encounter
Default principal diagnosis: inpatient Yes · outpatient Yes

Clinical InformationClinical

  • Bupropion

    a propiophenone-derived antidepressant and antismoking agent that inhibits the uptake of dopamine.

  • Nomifensine

    an isoquinoline derivative that prevents dopamine reuptake into synaptosomes. the maleate was formerly used in the treatment of depression. it was withdrawn worldwide in 1986 due to the risk of acute hemolytic anemia with intravascular hemolysis resulting from its use. in some cases, renal failure also developed. (from martindale, the extra pharmacopoeia, 30th ed, p266)

  • Viloxazine

    a morpholine derivative used as an antidepressant. it is similar in action to imipramine.

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.

SubstanceAccidentalSelf-harmAssaultUndeter­minedAdverse
Effect		Under­dosing
AmfebutamoneT43.291T43.292T43.293T43.294T43.295T43.296
BifemelaneT43.291T43.292T43.293T43.294T43.295T43.296
BupropionT43.291T43.292T43.293T43.294T43.295T43.296
DiclofensineT43.291T43.292T43.293T43.294T43.295T43.296
MinaprineT43.291T43.292T43.293T43.294T43.295T43.296
NomifensineT43.291T43.292T43.293T43.294T43.295T43.296
OxitriptanT43.291T43.292T43.293T43.294T43.295T43.296
PrazitoneT43.291T43.292T43.293T43.294T43.295T43.296
ThiazesimT43.291T43.292T43.293T43.294T43.295T43.296
TianeptineT43.291T43.292T43.293T43.294T43.295T43.296
ViloxazineT43.291T43.292T43.293T43.294T43.295T43.296

Patient EducationClinical

Antidepressants

Antidepressants are prescription medicines to treat depression. Depression is more than feeling a little sad or "blue" for a few days. It's a very common, serious medical illness that affects your mood and general mental health It can make you feel tired, hopeless, worried, or fearful. It can change your thinking, sleeping, and eating.

The full article covers:

  • What are antidepressants?
  • Are antidepressants used for other conditions?
  • What are the different types of antidepressants?
  • Which type of antidepressant is right for me?
  • How long do antidepressants take to work?
  • How long will I need to take an antidepressant?
  • What are the side effects of antidepressants?
  • What can I do to take antidepressants safely?

Read the full article at MedlinePlus

Courtesy of MedlinePlus, a service of the U.S. National Library of Medicine.

Convert T43.294A to ICD-9-CMHistory

The closest ICD-9-CM equivalents under the General Equivalence Mappings.

ICD-9-CM
969.09 Pois antidepressants NEC
ApproximateCombination The match is approximate, and more than one code can be needed to describe the source diagnosis. Confirm with contextual judgment.
ICD-9-CM
E980.3 Undeterm pois-psychotrop
ApproximateCombination The match is approximate, and more than one code can be needed to describe the source diagnosis. Confirm with contextual judgment.

Code HistoryHistory

FY 2016AddedAdded to the ICD-10-CM code setEffective October 1, 2015, the first year of ICD-10-CM.
FY 2017–2025No changes
FY 2026CurrentCurrent code set, no changesEffective October 1, 2025 through September 30, 2026.

Questions About T43.294AOverview

Is T43.294A (Poisoning by other antidepressants, undetermined) a billable code?

Yes. This is a billable ICD-10-CM code, specific enough to report poisoning by other antidepressants, undetermined, initial encounter on HIPAA-covered claims from October 1, 2025 through September 30, 2026.

What does the 7th character A in T43.294A mean?

The final character A marks the initial encounter: use it while the patient is receiving active treatment for poisoning by other antidepressants, undetermined, such as an emergency visit or first evaluation.

What MS-DRG does T43.294A group to?

When poisoning by other antidepressants, 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 T43.294A?

Under the General Equivalence Mappings, poisoning by other antidepressants, undetermined, initial encounter converts to ICD-9-CM 969.09 (pois antidepressants NEC) and E980.3 (undeterm pois-psychotrop). 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.