T42.0X5A is the authoritative medical code for Adverse effect of hydantoin derivatives, initial encounter. This classification is used in medical billing and clinical recording to specify the clinical criteria for adverse effect of hydantoin derivatives, initial encounter (ICD-10-CM T42.0X5A), ensuring healthcare documentation aligns with 2026 federal coding standards.
Billing Status: YES. This is a valid, specific, and billable ICD-10-CM reference.
Official Registry Overview & Definition
Adverse effect of hydantoin derivatives, initial encounter is a billable ICD-10-CM diagnosis code T42.0X5A. Includes: 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. Excludes1 (not coded here): toxic reaction to local anesthesia in pregnancy O29.3-. Excludes2 (not included here): drug dependence and related mental and behavioral disorders due to psychoactive substance use F10.--F19.-; 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 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: 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-). 7th character: The appropriate 7th character is to be added to each code from category T42.
Official Tabular Instructional Notes
Sequencing, inclusion, and exclusion notes published for T42.0X5A 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
Excludes1 — Not Coded Here
Conditions that can never be reported with this code; the two are mutually exclusive.
- toxic reaction to local anesthesia in pregnancy O29.3-
Excludes2 — Not Included Here
Conditions not covered by this code, but which may be reported alongside it when both are present.
- drug dependence and related mental and behavioral disorders due to psychoactive substance use F10.--F19.-
- 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 First
Underlying conditions that must be sequenced before this code.
- , 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.
- 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 Asked Questions (FAQ) & Clinical Guidance
Does T42.0X5A require a 7th character?
Yes. The appropriate 7th character is to be added to each code from category T42.
What can't be coded together with T42.0X5A?
Per Excludes1 instructions, T42.0X5A must not be reported with: toxic reaction to local anesthesia in pregnancy (O29.3-).
Can T42.0X5A be reported alongside related conditions?
Per Excludes2 instructions, T42.0X5A and the following may both be reported when both are present: drug dependence and related mental and behavioral disorders due to psychoactive substance use (F10.--F19.-); abuse and dependence of psychoactive substances (F10-F19); abuse of non-dependence-producing substances (F55.-); immunodeficiency due to drugs (D84.821).
Does T42.0X5A need to be sequenced after another code?
Yes. 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).
Is an additional code needed with T42.0X5A?
Use additional code(s) to specify: 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-).
Codes in This Family (40)
Official ICD-10-CM classifications in the same code family as T42.0X5A, with their registry titles.
- T42 — Poisoning by, adverse effect of and underdosing of antiepileptic, sedative- hypnotic and antiparkinsonism drugs
- T42.0 — Poisoning by, adverse effect of and underdosing of hydantoin derivatives
- T42.0X — Poisoning by, adverse effect of and underdosing of hydantoin derivatives
- T42.0X1 — Poisoning by hydantoin derivatives, accidental (unintentional)
- T42.0X1A — Poisoning by hydantoin derivatives, accidental (unintentional), initial encounter
- T42.0X1D — Poisoning by hydantoin derivatives, accidental (unintentional), subsequent encounter
- T42.0X1S — Poisoning by hydantoin derivatives, accidental (unintentional), sequela
- T42.0X2 — Poisoning by hydantoin derivatives, intentional self-harm
- T42.0X2A — Poisoning by hydantoin derivatives, intentional self-harm, initial encounter
- T42.0X2D — Poisoning by hydantoin derivatives, intentional self-harm, subsequent encounter
- T42.0X2S — Poisoning by hydantoin derivatives, intentional self-harm, sequela
- T42.0X3 — Poisoning by hydantoin derivatives, assault
- T42.0X3A — Poisoning by hydantoin derivatives, assault, initial encounter
- T42.0X3D — Poisoning by hydantoin derivatives, assault, subsequent encounter
- T42.0X3S — Poisoning by hydantoin derivatives, assault, sequela
- T42.0X4 — Poisoning by hydantoin derivatives, undetermined
- T42.0X4A — Poisoning by hydantoin derivatives, undetermined, initial encounter
- T42.0X4D — Poisoning by hydantoin derivatives, undetermined, subsequent encounter
- T42.0X4S — Poisoning by hydantoin derivatives, undetermined, sequela
- T42.0X5 — Adverse effect of hydantoin derivatives
- T42.0X5D — Adverse effect of hydantoin derivatives, subsequent encounter
- T42.0X5S — Adverse effect of hydantoin derivatives, sequela
- T42.0X6 — Underdosing of hydantoin derivatives
- T42.0X6A — Underdosing of hydantoin derivatives, initial encounter
- T42.0X6D — Underdosing of hydantoin derivatives, subsequent encounter
- T42.0X6S — Underdosing of hydantoin derivatives, sequela
- T42.1 — Poisoning by, adverse effect of and underdosing of iminostilbenes
- T42.1X — Poisoning by, adverse effect of and underdosing of iminostilbenes
- T42.1X1 — Poisoning by iminostilbenes, accidental (unintentional)
- T42.1X1A — Poisoning by iminostilbenes, accidental (unintentional), initial encounter
- T42.1X1D — Poisoning by iminostilbenes, accidental (unintentional), subsequent encounter
- T42.1X1S — Poisoning by iminostilbenes, accidental (unintentional), sequela
- T42.1X2 — Poisoning by iminostilbenes, intentional self-harm
- T42.1X2A — Poisoning by iminostilbenes, intentional self-harm, initial encounter
- T42.1X2D — Poisoning by iminostilbenes, intentional self-harm, subsequent encounter
- T42.1X2S — Poisoning by iminostilbenes, intentional self-harm, sequela
- T42.1X3 — Poisoning by iminostilbenes, assault
- T42.1X3A — Poisoning by iminostilbenes, assault, initial encounter
- T42.1X3D — Poisoning by iminostilbenes, assault, subsequent encounter
- T42.1X3S — Poisoning by iminostilbenes, assault, sequela
Associated Substances (12)
Substances from the official ICD-10-CM Table of Drugs and Chemicals that map to this code.
- Albutoin
- Dilantin
- Diphenylhydantoin
- Epanutin
- Ethotoin
- Hydantoin derivative NEC
- Mephenytoin
- Metetoin
- Methetoin
- Methoin
- Phenantoin
- Phenytoin
Related Codes & Numerical Sequence (Crawl Map)
Search engines and indexers are advised to traverse adjacent medical codes in this sub-chapter range to find correlated diagnoses or therapeutic procedures:
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ICD Code T46.0X5A
Adverse effect of cardiac-stimulant glycosides and drugs of similar action, initial encounter
ICD Code T47.0X5A
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