T42
Poisoning by, adverse effect of and underdosing of antiepileptic, sedative- hypnotic and antiparkinsonism drugs
T42 is a non-billable ICD-10-CM code category for poisoning by, adverse effect of and underdosing of antiepileptic, sedative- hypnotic and antiparkinsonism drugs. Report a more specific code from it instead. It is part of the FY2027 code set, effective October 1, 2026. The more specific codes under it are T42.0 Poisoning by, adverse effect of and underdosing of hydantoin derivatives; T42.1 Poisoning by, adverse effect of and underdosing of iminostilbenes; T42.2 Poisoning by, adverse effect of and underdosing of succinimides and oxazolidinediones; T42.3 Poisoning by, adverse effect of and underdosing of barbiturates and 5 more. Its coding notes include a Code first instruction, a Use additional code instruction, 1 Excludes1 entry and 8 Excludes2 entries.
7th characters
Every code below needs one of these.
The appropriate 7th character is to be added to each code from category T42
- Ainitial encounter
- Dsubsequent encounter
- Ssequela
Guidelines tips
From the FY2027 Official Guidelines. ICD10Ref adds no rules of its own.
The 7th character depends on whether the patient is in active treatment, not on who sees the patient. An aftercare Z code is not used for injury aftercare.
T36-T65 codes already include the substance and the intent, so no additional external cause code is required. Do not code directly from the Table of Drugs and Chemicals.
Code first
If the underlying condition listed here is present and known, sequence it first.
Also from chapter/block level (7 notes)
Use additional code
Add the listed code as a secondary code, if known.
Also from chapter/block level (5 notes)
- code to identify any retained foreign body, if applicable (Z18.-)
Excludes1
Not coded here. The listed conditions generally should not be reported together.
Excludes2
Not included here. Both codes may be reported if the patient has both conditions.
- drug dependence and related mental and behavioral disorders due to psychoactive substance use (F10.--F19.-)
Also from chapter/block level (7 notes)
- birth trauma (P10-P15)
- obstetric trauma (O70-O71)
Includes
Further defines or gives examples of the content of the category.
Also from chapter/block level (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
Notes
Also from chapter/block level (3 notes)
- The drug giving rise to the adverse effect should be identified by use of codes from categories T36-T50 with fifth or sixth character 5.
- Use secondary code(s) from Chapter 20, External causes of morbidity, to indicate cause of injury. Codes within the T section that include the external cause do not require an additional external cause code
- The chapter uses the S-section for coding different types of injuries related to single body regions and the T-section to cover injuries to unspecified body regions as well as poisoning and certain other consequences of external causes.
More specific codes under T42 9
- T42.0Poisoning by, adverse effect of and underdosing of hydantoin derivativesHeader
- T42.1Poisoning by, adverse effect of and underdosing of iminostilbenesHeader
- T42.2Poisoning by, adverse effect of and underdosing of succinimides and oxazolidinedionesHeader
- T42.3Poisoning by, adverse effect of and underdosing of barbituratesHeader
- T42.4Poisoning by, adverse effect of and underdosing of benzodiazepinesHeader
- T42.5Poisoning by, adverse effect of and underdosing of mixed antiepilepticsHeader
- T42.6Poisoning by, adverse effect of and underdosing of other antiepileptic and sedative-hypnotic drugsHeader
- T42.7Poisoning by, adverse effect of and underdosing of unspecified antiepileptic and sedative-hypnotic drugsHeader
- T42.8Poisoning by, adverse effect of and underdosing of antiparkinsonism drugs and other central muscle-tone depressantsHeader