2026 ICD-10-CM Diagnosis Code T42Poisoning by, adverse effect of and underdosing of antiepileptic, sedative- hypnotic and antiparkinsonism drugs
T42 is a non-billable ICD-10-CM category code for poisoning by, adverse effect of and underdosing of antiepileptic, sedative- hypnotic and antiparkinsonism drugs, so it cannot be submitted on claims. Use a more specific code from this category instead, such as T42.0X1A, T42.0X1D, T42.0X1S, and T42.0X2A.
Code Identity
Code Classification
Specific Coding for Antiepileptic, sedative- hypnotic and antiparkinsonism drugsOverview
Non-specific codes like T42 require more characters. Use one of these billable codes instead:
T42.0 for Poisoning by, adverse effect of and underdosing of hydantoin derivatives
T42.0X for Poisoning by, adverse effect of and underdosing of hydantoin derivatives
T42.1 for Poisoning by, adverse effect of and underdosing of iminostilbenes
T42.1X for Poisoning by, adverse effect of and underdosing of iminostilbenes
T42.2 for Poisoning by, adverse effect of and underdosing of succinimides and oxazolidinediones
T42.2X for Poisoning by, adverse effect of and underdosing of succinimides and oxazolidinediones
T42.3 for Poisoning by, adverse effect of and underdosing of barbiturates
T42.3X for Poisoning by, adverse effect of and underdosing of barbiturates
T42.4 for Poisoning by, adverse effect of and underdosing of benzodiazepines
T42.4X for Poisoning by, adverse effect of and underdosing of benzodiazepines
T42.5 for Poisoning by, adverse effect of and underdosing of mixed antiepileptics
T42.5X for Poisoning by, adverse effect of and underdosing of antiepileptics
T42.6 for Poisoning by, adverse effect of and underdosing of other antiepileptic and sedative-hypnotic drugs
T42.6X for Poisoning by, adverse effect of and underdosing of other antiepileptic and sedative-hypnotic drugs
T42.7 for Poisoning by, adverse effect of and underdosing of unspecified antiepileptic and sedative-hypnotic drugs
T42.71 for Poisoning by unspecified antiepileptic and sedative-hypnotic drugs, accidental (unintentional)
T42.72 for Poisoning by unspecified antiepileptic and sedative-hypnotic drugs, intentional self-harm
T42.73 for Poisoning by unspecified antiepileptic and sedative-hypnotic drugs, assault
T42.74 for Poisoning by unspecified antiepileptic and sedative-hypnotic drugs, undetermined
T42.75 for Adverse effect of unspecified antiepileptic and sedative-hypnotic drugs
T42.76 for Underdosing of unspecified antiepileptic and sedative-hypnotic drugs
T42.8 for Poisoning by, adverse effect of and underdosing of antiparkinsonism drugs and other central muscle-tone depressants
T42.8X for Poisoning by, adverse effect of and underdosing of antiparkinsonism drugs and other central muscle-tone depressants
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 antiepileptic, sedative- hypnotic and antiparkinsonism drugs (T42). 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.
Tabular List NotesGuidance
Coding notes and annotation back-references applicable to this code.
Type 2 Excludes
- drug dependence and related mental and behavioral disorders due to psychoactive substance use F10 F19
7th Character Note
- The appropriate 7th character is to be added to each code from category T42
7th Character
- A - initial encounter
- D - subsequent encounter
- S - sequela
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.
Certain ICD-10-CM categories have applicable 7th characters. The applicable 7th character is required for all codes within the category, or as the notes in the Tabular List instruct. The 7th character must always be the 7th character in the data field. If a code that requires a 7th character is not 6 characters, a placeholder X must be used to fill in the empty characters.
Indicates that a seventh character is to be assigned to codes in a subcategory.
Patient EducationClinical
Drug Reactions
Most of the time, medicines make our lives better. They reduce aches and pains, fight infections, and control problems such as high blood pressure or diabetes. But medicines can also cause unwanted reactions, such as drug interactions, side effects, and allergies.
The full article covers:
- What is a drug interaction?
- What are side effects?
- What are drug allergies?
- How can I stay safe when taking medicines?
Read the full article at MedlinePlus
Courtesy of MedlinePlus, a service of the U.S. National Library of Medicine.
Code HistoryHistory
Questions About T42Overview
Is T42 a billable code?
No. This is a category header that groups the codes for poisoning by, adverse effect of and underdosing of antiepileptic, sedative- hypnotic and antiparkinsonism drugs, and headers cannot be submitted on claims. Claims for poisoning by, adverse effect of and underdosing of antiepileptic, sedative- hypnotic and antiparkinsonism drugs need a more specific code from this category, such as T42.0X1A, T42.0X1D, and T42.0X1S.
