2026 ICD-10-CM Diagnosis Code T42.3X1SPoisoning by barbiturates, accidental (unintentional), sequela
T42.3X1S is a billable ICD-10-CM diagnosis code for poisoning by barbiturates, accidental (unintentional), sequela. The 7th character S marks it as a sequela code, which reports a problem that remains after the original condition has resolved. It is valid on HIPAA claims for fiscal year 2026 (October 1, 2025 through September 30, 2026) and groups to MS-DRG 922 through 923. The code is exempt from POA reporting. In AHRQ's Clinical Classifications Software (CCSR), this diagnosis falls under Poisoning/toxic effect/adverse effects/underdosing, sequela.
Code Identity
Code Classification
Present on Admission (POA)Billing
T42.3X1S is exempt from POA reporting on inpatient claims to general acute care hospitals. Review other POA exempt codes.
Approximate SynonymsGuidance
Alternate terms and clinical phrases that map to this code.
- Accidental amylobarbitone overdose
- Accidental butabarbitone overdose
- Accidental cyclobarbitone overdose
- Accidental cyclobarbitone poisoning
- Accidental methylphenobarbitone overdose
- Accidental methylphenobarbitone poisoning
- Accidental phenobarbitone overdose
- Accidental poisoning by amobarbital
- Accidental poisoning by barbitone
- Accidental poisoning by barbiturates
- Accidental poisoning by butabarbitone
- Accidental poisoning by pentobarbitone
- Accidental poisoning by phenobarbitone
- Accidental poisoning by quinalbarbitone
- Accidental quinalbarbitone overdose
- Amylobarbitone overdose
- Barbiturate overdose
- Butabarbitone overdose
- Cyclobarbitone overdose
- Cyclobarbitone poisoning
- Methylphenobarbitone overdose
- Methylphenobarbitone poisoning
- Phenobarbitone overdose
- Poisoning by amobarbital
- Poisoning by barbital
- Poisoning by barbiturate
- Poisoning by butabarbital
- Poisoning by pentobarbital
- Poisoning by phenobarbital
- Poisoning by secobarbital
- Quinalbarbitone overdose
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.
Clinical ClassificationClinical
AHRQ’s CCSR groups this code into broader clinical categories.
Clinical InformationClinical
Barbital
a long-acting barbiturate that depresses most metabolic processes at high doses. it is used as a hypnotic and sedative and may induce dependence. barbital is also used in veterinary practice for central nervous system depression.Hexobarbital
a barbiturate that is effective as a hypnotic and sedative.Mephobarbital
a barbiturate that is metabolized to phenobarbital. it has been used for similar purposes, especially in epilepsy, but there is no evidence mephobarbital offers any advantage over phenobarbital.Pentobarbital
a short-acting barbiturate that is effective as a sedative and hypnotic (but not as an anti-anxiety) agent and is usually given orally. it is prescribed more frequently for sleep induction than for sedation but, like similar agents, may lose its effectiveness by the second week of continued administration. (from ama drug evaluations annual, 1994, p236)Phenobarbital
a barbituric acid derivative that acts as a nonselective central nervous system depressant. it potentiates gamma-aminobutyric acid action on gaba-a receptors, and modulates chloride currents through receptor channels. it also inhibits glutamate induced depolarizations.Secobarbital
a barbiturate that is used as a sedative. secobarbital is reported to have no anti-anxiety activity.
Table of Drugs and ChemicalsClinical
Substances in the Table of Drugs and Chemicals that reference this code family. Always confirm in the Tabular List before coding.
Patient EducationClinical
Medication Errors
Medicines treat infectious diseases, prevent problems from chronic diseases, and ease pain. But medicines can also cause harmful reactions if not used correctly. Errors can happen in the hospital, at the health care provider's office, at the pharmacy, or at home. You can help prevent errors by:
Read the full article at MedlinePlus
Courtesy of MedlinePlus, a service of the U.S. National Library of Medicine.
Convert T42.3X1S to ICD-9-CMHistory
The closest ICD-9-CM equivalents under the General Equivalence Mappings.
Code HistoryHistory
Questions About T42.3X1SOverview
Is T42.3X1S (Poisoning by barbiturates, accidental (unintentional)) a billable code?
Yes. This is a billable ICD-10-CM code, specific enough to report poisoning by barbiturates, accidental (unintentional), sequela on HIPAA-covered claims from October 1, 2025 through September 30, 2026.
What does the 7th character S in T42.3X1S mean?
The final character S makes this a sequela code: it reports a lingering problem that remains after the poisoning by barbiturates, accidental (unintentional) itself has resolved, not the original event.
What MS-DRG does T42.3X1S group to?
When poisoning by barbiturates, accidental (unintentional), sequela is the principal diagnosis on an inpatient stay, it groups to MS-DRG 922, 923, with relative weights from 1.0177 to 1.7494 depending on complications. Higher weights mean higher Medicare reimbursement.
Is T42.3X1S exempt from POA reporting?
Yes. CMS lists this code among those exempt from present on admission reporting, so hospitals do not assign a POA indicator for poisoning by barbiturates, accidental (unintentional), sequela on inpatient claims.
What is the ICD-9 equivalent of T42.3X1S?
Under the General Equivalence Mappings, poisoning by barbiturates, accidental (unintentional), sequela converts to ICD-9-CM 909.0 (late eff drug poisoning) and E929.2 (late eff acc poisoning). The mapping is approximate, so confirm the match fits the documentation.
Footnotes
[1] Not chronic - A diagnosis code that does not fit the criteria for chronic condition (duration, ongoing medical treatment, and limitations) is considered not chronic. Some codes designated as not chronic are acute conditions. Other diagnosis codes that indicate a possible chronic condition, but for which the duration of the illness is not specified in the code description (i.e., we do not know the condition has lasted 12 months or longer) also are considered not chronic.
