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T42.6 vs T43.655

T42.6 (Poisoning by, adverse effect of and underdosing of other antiepileptic and sedative-hypnotic drugs) compared with T43.655 (Adverse effect of methamphetamines), from the official CMS tabular data.

Current data releases:ICD-10-CM FY2027 · ICD-10-PCS FY2027 · HCPCS October 2026 · MS-DRG v44 · Medicare Code Editor v44.0 · NCCI PTP Q4 2026 · MUE Q4 2026 · NCD code lists 2026-01 · LCD export September 28, 2026 · All releases and sources

Summary

These codes can be reported together when both conditions are documented, because T43.655 lists T42.6 under Excludes2, which marks them as distinct conditions.

Official rule
What is different?

The conditions named.T42.6 is “Poisoning by, adverse effect of and underdosing of other antiepileptic and sedative-hypnotic drugs”; T43.655 is “Adverse effect of methamphetamines”.

Registry fact

Can these codes be reported together?

Yes, when both are documented.T43.655 lists T42.6 under Excludes2: “methaqualone (T42.6-)”. Excludes2 marks distinct conditions that may both be reported when both are documented.

Official ruleGuide: Excludes1 vs Excludes2

Is there an Excludes2 relationship?

Yes.T43.655’s tabular entry: “methaqualone (T42.6-)”. The note covers T42.6.

Official ruleGuide: Excludes1 vs Excludes2

Is one a parent or header code?

Both are headers.Both are non-billable headers, and neither contains the other.

Registry fact

Nothing found in 3 other checks; 1 check does not apply
Is there an Excludes1 relationship?

None.Neither entry carries an Excludes1 note that names the other code. T42.6 carries 2 Excludes1 notes and T43.655 carries 2 Excludes1 notes covering other codes; the side-by-side table quotes them.

Official rule

Is one more specific?

Not comparable.The codes sit in different categories; specificity is only comparable within one category.

Are there sequencing instructions?

None.Neither entry carries a Code First or Use Additional Code note that names the other.

Official rule

Are there other coding relationships?

None found.No laterality, encounter-phase, Table of Neoplasms, Table of Drugs and Chemicals, or history-versus-active-disease relationship links these codes.

MedCoder-derived

Official rule: a tabular instructional note or a section of the ICD-10-CM Official Guidelines, quoted as published. Registry fact: the codes’ own published attributes (titles, billable status, position in the hierarchy, code set). MedCoder-derived: a reading MedCoder computes from those facts; it is not itself a rule. How to read the labels

Can these codes be reported together?

Informational

Excludes2 relationship

T43.655
Adverse effect of methamphetamines
↔
T42.6
Poisoning by, adverse effect of and underdosing of other antiepileptic and sedative-hypnotic drugs

What we found

Yes, when both are documented.T43.655 carries an Excludes2 note covering T42.6: “methaqualone (T42.6-)”

Excludes2 marks distinct conditions — both may be reported when both are documented.

What to review

Report both only when the documentation supports both conditions; otherwise report the one documented.

Guide: Excludes1 vs Excludes2Check these on a claim

Why it matters

An Excludes2 note means the excluded condition is not part of the code above it, but a patient can have both. Report both when both are documented.

Source / rule

CMS ICD-10-CM tabular instructional notes

Official guidance behind these answers

  • Section I.A.12.b — Excludes2 · applies to: Excludes2

    A type 2 Excludes note represents “Not included here.” An excludes2 note indicates that the condition excluded is not part of the condition represented by the code, but a patient may have both conditions at the same time. When an Excludes2 note appears under a code, it is acceptable to use both the code and the excluded code together, when appropriate.

    ICD-10-CM Official Guidelines FY2027

Quoted from the ICD-10-CM Official Guidelines for Coding and Reporting in effect for the release shown. The tabular notes above are the code-level instruction; these sections are the convention that says how such a note is applied. Source document (CMS PDF) · Release and checksum

Side by side

Similar descriptions do not make codes interchangeable. The documentation and the official instructions decide which code applies.

Official descriptionDiffers
T42.6

Poisoning by, adverse effect of and underdosing of other antiepileptic and sedative-hypnotic drugs

T43.655

Adverse effect of methamphetamines

StatusDiffers
T42.6
Non-billable header

A header is not reported on a claim; a code beneath it is.

Report instead: T42.6X1A, T42.6X1D, T42.6X1S, T42.6X2A, T42.6X2D

T43.655
Non-billable header

A header is not reported on a claim; a code beneath it is.

Report instead: T43.655A, T43.655D, T43.655S

Excludes1Differs
Only at T42.6
  • poisoning by, adverse effect of and underdosing of carbamazepine (T42.1-)
Only at T43.655
  • poisoning by, adverse effect of and underdosing of cocaine (T40.5-)
Shared by both codes (1 note)
  • toxic reaction to local anesthesia in pregnancy (O29.3-)
Excludes2Differs
Only at T42.6
  • drug dependence and related mental and behavioral disorders due to psychoactive substance use (F10.--F19.-)
Only at T43.655
  • appetite depressants (T50.5-)
  • barbiturates (T42.3-)
  • benzodiazepines (T42.4-)
  • drug dependence and related mental and behavioral disorders due to psychoactive substance use (F10.- -F19.-)
  • methaqualone (T42.6-)
  • psychodysleptics [hallucinogens] (T40.7-T40.9-)
Shared by both codes (5 notes)
  • abuse and dependence of psychoactive substances (F10-F19)
  • abuse of non-dependence-producing substances (F55.-)
  • immunodeficiency due to drugs (D84.821)
  • drug reaction and poisoning affecting newborn (P00-P96)
  • pathological drug intoxication (inebriation) (F10-F19)
Code firstSame for both
  • , 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 codeSame for both
  • 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-)
CategoryDiffers
T42.6

T42 Poisoning by, adverse effect of and underdosing of antiepileptic, sedative- hypnotic and antiparkinsonism drugs

T43.655

T43 Poisoning by, adverse effect of and underdosing of psychotropic drugs, not elsewhere classified

ChapterSame for both

S00-T88 — Injury, Poisoning and Certain Other Consequences of External Causes (S00-T88)

IncludesDiffers
Only at T42.6
  • Poisoning by, adverse effect of and underdosing of methaqualone
  • Poisoning by, adverse effect of and underdosing of valproic acid
Only at T43.655

No note of its own beyond the shared notes

Shared by both codes (4 notes)
  • 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
7th characterDiffers
T42.6
  • The appropriate 7th character is to be added to each code from category T42
T43.655
  • The appropriate 7th character is to be added to each code from category T43

No Code also note at either code.

Notes are the code’s own tabular entry, quoted as published. A note that names the other code is the one the verdict above rests on. In a row that differs, each code’s own notes are listed under it, and the notes every code shares are listed once beneath them.

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Derived from the official CMS ICD-10-CM tabular data (FY2027). A coding-rule comparison, not billing advice: payer-specific edits and medical-necessity policy are outside its scope. All data sources