ICD-10-CM 2027 diagnosis code
T42.0X5Adverse effect of hydantoin derivatives
T42.0X5 is a header code, so it can't be reported by itself. Choose one of the 3 more specific codes beneath it and add the required 7th character.
Source: official FY2027 ICD-10-CM release from CDC/NCHS and CMS, effective October 1, 2026. Updated September 29, 2026. About our data
About T42.0X5
T42.0X5 is the ICD-10-CM diagnosis code for adverse effect of hydantoin derivatives. It belongs to category T42 (poisoning by, adverse effect of and underdosing of antiepileptic, sedative- hypnotic and antiparkinsonism drugs), block T36-T50 (poisoning by, adverse effects of and underdosing of drugs, medicaments and biological substances) and chapter 19 (injury, poisoning and certain other consequences of external causes). It is a header code, so it can't be reported by itself; one of its 3 subcodes must be used instead.
Within T42.0X (poisoning by, adverse effect of and underdosing of hydantoin derivatives), T42.0X5 is specifically for adverse effect of hydantoin derivatives. Related codes cover poisoning by hydantoin derivatives, accidental (unintentional) (T42.0X1), poisoning by hydantoin derivatives, intentional self-harm (T42.0X2), poisoning by hydantoin derivatives, assault (T42.0X3), poisoning by hydantoin derivatives, undetermined (T42.0X4) and underdosing of hydantoin derivatives (T42.0X6).
Codes in this range require a 7th character: A for initial encounter, D for subsequent encounter and S for sequela. Use placeholder "X" characters to fill any empty positions before the 7th character.
It has been part of ICD-10-CM since the code set took effect on October 1, 2015 and hasn't changed since.
7th character
The appropriate 7th character is to be added to each code from category T42
Notes that apply from higher levels
Instructions written at a parent level also apply to T42.0X5.
Broader instructions also apply from T36-T50 Poisoning by, adverse effects of and underdosing of drugs, medicaments and biological substances and Chapter 19: Injury, poisoning and certain other consequences of external causes.
Table of Drugs & Neoplasms entries
- Albutoin — Adverse effect
- Anticonvulsant › hydantoin — Adverse effect
- Dilantin — Adverse effect
- Diphenylhydantoin — Adverse effect
- Epanutin — Adverse effect
- Ethotoin — Adverse effect
- Hydantoin derivative NEC — Adverse effect
- Mephenytoin — Adverse effect
- Metetoin — Adverse effect
- Methetoin — Adverse effect
- Methoin — Adverse effect
- Phenantoin — Adverse effect
- Phenytoin — Adverse effect
Code history
- 2016
- 2017
- 2018
- 2019
- 2020
- 2021
- 2022
- 2023
- 2024
- 2025
- 2026
- 2027
- FY2016 (effective 10/1/2015): Added (first year of ICD-10-CM)
- No changes since FY2016.
Common questions about T42.0X5
Is T42.0X5 billable?
- No. T42.0X5 is a header code. Report one of its more specific subcodes instead.