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T40.491A ICD-10-CM Code: Poisoning by other synthetic narcotics, accidental (unintentional), initial encounter

Billing Status: YES. This is a valid, specific, and billable ICD-10-CM reference.

Inpatient Payment Groups (MS-DRG)

MS-DRGs this diagnosis helps define, as principal or secondary, per the CMS ICD-10-CM/PCS MS-DRG Definitions Manual v43.0, Appendix B.

  • MS-DRG 917 — POISONING AND TOXIC EFFECTS OF DRUGS WITH MCC (MDC 21)
  • MS-DRG 918 — POISONING AND TOXIC EFFECTS OF DRUGS WITHOUT MCC (MDC 21)

A diagnosis appearing in a group's logic does not by itself determine the DRG assigned to a stay; the grouper uses the full claim.

Risk Adjustment (CMS-HCC)

Payment categories this diagnosis maps to under CMS-HCC V28, payment year 2026.

  • HCC 137 — Drug Use Disorder, Moderate/Severe, or Drug Use with Non-Psychotic Complications (supersedes HCC 138, HCC 139)

Risk scores depend on the enrollee's full accepted diagnosis set and segment; a category mapping alone does not determine payment.

Official Registry Overview & Definition

Poisoning by other synthetic narcotics, accidental (unintentional), initial encounter is a billable ICD-10-CM diagnosis code (T40.491A).

Official Tabular Instructional Notes

Sequencing, inclusion, and exclusion notes published for T40.491A in the official ICD-10-CM tabular list.

Includes

Conditions the official ICD-10-CM tabular list includes under this code.

  • adverse effect of correct substance properly administered
  • poisoning by overdose of substance
  • poisoning by wrong substance given or taken in error
  • underdosing by (inadvertently) (deliberately) taking less substance than prescribed or instructed

Inclusion Terms

Alternative terms the tabular list files under this code.

  • Poisoning by other synthetic narcotics NOS

Excludes1 — Not Coded Here

Conditions generally not reported together with this code (Excludes1) -- an error unless the two conditions are documented as unrelated to each other (ICD-10-CM Official Guidelines, Section I.A.12.a).

Excludes2 — Not Included Here

Conditions not covered by this code, but which may be reported alongside it when both are present.

Code First

Underlying conditions that must be sequenced before this code.

  • Code first, for adverse effects, the nature of the adverse effect, such as:
  • adverse effect NOS (T88.7)
  • aspirin gastritis (K29.-)
  • blood disorders (D56-D76)
  • contact dermatitis (L23-L25)
  • dermatitis due to substances taken internally (L27.-)
  • nephropathy (N14.0-N14.2)

Use Additional Code

Supplementary codes the tabular list directs you to add.

  • Use additional code(s) to specify:
  • manifestations of poisoning
  • underdosing or failure in dosage during medical and surgical care (Y63.6, Y63.8-Y63.9)
  • underdosing of medication regimen (Z91.12-, Z91.13-)

Frequently Compared Codes

The official Excludes notes on T40.491A name these codes. Each comparison page covers when the two can — or must not — be reported together.

Change history

  • FY2021 — 2020-10-01
    Added to the code set
    Poisoning by other synthetic narcotics, accidental (unintentional), initial encounter
    FY2021 changes

Verify Before Coding

  • No Medicare Code Editor or MS-DRG Definitions Manual restrictions apply to this code.

From the code registry, the Medicare Code Editor, and the MS-DRG Definitions Manual. Check it against a full claim.

Contextual Map

Every relationship of T40.491A in one view: hierarchy, official tabular instructions in both directions, clinical classification, risk adjustment, MS-DRG participation, index terms and change history — each edge carrying the CMS source it derives from.

Hierarchy

  • S00-T88 — Chapter 19: Injury, Poisoning and Certain Other Consequences of External Causes (S00-T88) (S00-T88) [Hierarchy]
  • T36-T50 — Poisoning by, adverse effects of and underdosing of drugs, medicaments and biological substances [Hierarchy]
  • T40-T41 — Analgesics & Antipyretics [Hierarchy]

Clinical classification (CCSR)

  • INJ022 — Poisoning by drugs, initial encounter [CCSR]
  • EXT014 — External cause codes: poisoning by drug [CCSR]
  • EXT020 — External cause codes: intent of injury, accidental/unintentional [CCSR]
  • MBD018 — Opioid-related disorders [CCSR]

Risk adjustment (CMS-HCC)

  • HCC 137 — Drug Use Disorder, Moderate/Severe, or Drug Use with Non-Psychotic Complications [CMS-HCC]: “Drug Use Disorder, Moderate/Severe, or Drug Use with Non-Psychotic Complications — supersedes HCC 138 (Drug Use Disorder, Mild, Uncomplicated, Except Cannabis), HCC 139 (Alcohol Use Disorder, Moderate/Severe, or Alcohol Use with Specified Non-Psychotic Complications)”

Potential MS-DRG

  • DRG 917 — POISONING AND TOXIC EFFECTS OF DRUGS WITH MCC [MS-DRG]: “POISONING AND TOXIC EFFECTS OF DRUGS WITH MCC (MDC 21)”
  • DRG 918 — POISONING AND TOXIC EFFECTS OF DRUGS WITHOUT MCC [MS-DRG]: “POISONING AND TOXIC EFFECTS OF DRUGS WITHOUT MCC (MDC 21)”

MDC crossing · procedures (32029)

  • MDC 21 — Injuries, Poisonings and Toxic Effects of Drugs [MDC crossing]: “Injuries, Poisonings and Toxic Effects of Drugs — the grouper's crossing between diagnoses and procedures: a principal diagnosis sets the MDC, and same-MDC procedures move the stay to its surgical DRGs.”
  • 0016070 — Bypass Cerebral Ventricle to Nasopharynx with Autologous Tissue Substitute, Open Approach [Same-MDC procedure]: “Bypass Cerebral Ventricle to Nasopharynx with Autologous Tissue Substitute, Open Approach — grouped in MDC 21, the procedure side of this code's crossing.” · check together
  • 0016071 — Bypass Cerebral Ventricle to Mastoid Sinus with Autologous Tissue Substitute, Open Approach [Same-MDC procedure]: “Bypass Cerebral Ventricle to Mastoid Sinus with Autologous Tissue Substitute, Open Approach — grouped in MDC 21, the procedure side of this code's crossing.” · check together
  • 0016072 — Bypass Cerebral Ventricle to Atrium with Autologous Tissue Substitute, Open Approach [Same-MDC procedure]: “Bypass Cerebral Ventricle to Atrium with Autologous Tissue Substitute, Open Approach — grouped in MDC 21, the procedure side of this code's crossing.” · check together
  • 0016073 — Bypass Cerebral Ventricle to Blood Vessel with Autologous Tissue Substitute, Open Approach [Same-MDC procedure]: “Bypass Cerebral Ventricle to Blood Vessel with Autologous Tissue Substitute, Open Approach — grouped in MDC 21, the procedure side of this code's crossing.” · check together
  • 0016074 — Bypass Cerebral Ventricle to Pleural Cavity with Autologous Tissue Substitute, Open Approach [Same-MDC procedure]: “Bypass Cerebral Ventricle to Pleural Cavity with Autologous Tissue Substitute, Open Approach — grouped in MDC 21, the procedure side of this code's crossing.” · check together
  • and 32024 more

Drugs & chemicals (24)

  • Alphaprodine — Alphaprodine — Poisoning, Accidental (unintentional) [Drug table]: “Alphaprodine (Poisoning, Accidental (unintentional))”
  • Anileridine — Anileridine — Poisoning, Accidental (unintentional) [Drug table]: “Anileridine (Poisoning, Accidental (unintentional))”
  • Bezitramide — Bezitramide — Poisoning, Accidental (unintentional) [Drug table]: “Bezitramide (Poisoning, Accidental (unintentional))”
  • Buprenorphine — Buprenorphine — Poisoning, Accidental (unintentional) [Drug table]: “Buprenorphine (Poisoning, Accidental (unintentional))”
  • Butorphanol — Butorphanol — Poisoning, Accidental (unintentional) [Drug table]: “Butorphanol (Poisoning, Accidental (unintentional))”
  • Dextromoramide — Dextromoramide — Poisoning, Accidental (unintentional) [Drug table]: “Dextromoramide (Poisoning, Accidental (unintentional))”
  • Dextropropoxyphene — Dextropropoxyphene — Poisoning, Accidental (unintentional) [Drug table]: “Dextropropoxyphene (Poisoning, Accidental (unintentional))”
  • Dipipanone — Dipipanone — Poisoning, Accidental (unintentional) [Drug table]: “Dipipanone (Poisoning, Accidental (unintentional))”
  • and 16 more

Nearest codes (40)

  • T40 — Poisoning by, adverse effect of and underdosing of narcotics and psychodysleptics [hallucinogens] [Sibling]
  • T40.422D — Poisoning by tramadol, intentional self-harm, subsequent encounter [Sibling]
  • T40.422S — Poisoning by tramadol, intentional self-harm, sequela [Sibling]
  • T40.423 — Poisoning by tramadol, assault [Sibling]
  • T40.423A — Poisoning by tramadol, assault, initial encounter [Sibling]
  • T40.423D — Poisoning by tramadol, assault, subsequent encounter [Sibling]
  • T40.423S — Poisoning by tramadol, assault, sequela [Sibling]
  • T40.424 — Poisoning by tramadol, undetermined [Sibling]
  • and 32 more

Change history

  • FY2021 — Added to the code set [Change history]

Relationships & Classification

Clinical classification (AHRQ CCSR):INJ022 — Poisoning by drugs, initial encounter (default); EXT014 — External cause codes: poisoning by drug; EXT020 — External cause codes: intent of injury, accidental/unintentional; MBD018 — Opioid-related disorders.

Clinical Classifications Software Refined (CCSR) for ICD-10-CM Diagnoses. Healthcare Cost and Utilization Project (HCUP), Agency for Healthcare Research and Quality.

Potential MS-DRG Relationships (FY2026)

Not on the CMS CC/MCC list — as a secondary diagnosis this code does not change MS-DRG severity.

Named in the grouper logic of 2 MS-DRGs: DRG 917 (MDC 21), DRG 918 (MDC 21).

From the CMS MS-DRG Definitions Manual (Appendices B and C). Actual DRG assignment depends on the complete claim.

Frequently Asked Questions (FAQ) & Clinical Guidance

Does T40.491A require a 7th character?

Yes. The appropriate 7th character is to be added to each code from category T40.

Nearest Codes in This Family

Official ICD-10-CM classifications closest to T40.491A in its code family, with their registry titles.

  • T40.426A — Underdosing of tramadol, initial encounter
  • T40.426D — Underdosing of tramadol, subsequent encounter
  • T40.426S — Underdosing of tramadol, sequela
  • T40.49 — Poisoning by, adverse effect of and underdosing of other synthetic narcotics
  • T40.491 — Poisoning by other synthetic narcotics, accidental (unintentional)
  • T40.491D — Poisoning by other synthetic narcotics, accidental (unintentional), subsequent encounter
  • T40.491S — Poisoning by other synthetic narcotics, accidental (unintentional), sequela
  • T40.492 — Poisoning by other synthetic narcotics, intentional self-harm
  • T40.492A — Poisoning by other synthetic narcotics, intentional self-harm, initial encounter
  • T40.492D — Poisoning by other synthetic narcotics, intentional self-harm, subsequent encounter

View all codes in the T40 family

Associated Substances (24)

Substances from the official ICD-10-CM Table of Drugs and Chemicals that map to this code.

  • Alphaprodine
  • Anileridine
  • Bezitramide
  • Buprenorphine
  • Butorphanol
  • Dextromoramide
  • Dextropropoxyphene
  • Dipipanone
  • Eptazocine
  • Ethoheptazine
  • Isonipecaine
  • Ketobemidone
  • Levopropoxyphene
  • Levorphanol
  • Meperidine
  • Nalbuphine
  • Pentazocine
  • Pethidine
  • Phenazocine
  • Phenoperidine
  • Piritramide
  • Profadol
  • Propoxyphene
  • Tilidine