2027 ICD-10-CM Diagnosis Code T40.491SPoisoning by other synthetic narcotics, accidental (unintentional), sequela
T40.491S is a billable ICD-10-CM diagnosis code for poisoning by other synthetic narcotics, 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 2027 (October 1, 2026 through September 30, 2027) 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 Mental and substance use disorders; sequela; and Poisoning/toxic effect/adverse effects/underdosing, sequela.
Code Identity
Code Classification
Present on Admission (POA)Billing
T40.491S is exempt from POA reporting on inpatient claims to general acute care hospitals. Review the other POA exempt codes in Poisoning by, adverse effect of and underdosing of drugs, medicaments and biological substances (T36-T50).
Approximate SynonymsGuidance
Alternate terms and clinical phrases that map to this code.
- Accidental acetaminophen and/or dextropropoxyphene overdose
- Accidental acetaminophen and/or dextropropoxyphene poisoning
- Accidental buprenorphine overdose
- Accidental buprenorphine poisoning
- Accidental dextromoramide overdose
- Accidental dextromoramide poisoning
- Accidental dextropropoxyphene overdose
- Accidental dextropropoxyphene poisoning
- Accidental dipipanone overdose
- Accidental dipipanone poisoning
- Accidental levorphanol overdose
- Accidental levorphanol poisoning
- Accidental meperidine overdose
- Accidental nalbuphine overdose
- Accidental nalbuphine poisoning
- Accidental pentazocine overdose
- Accidental phenazocine overdose
- Accidental phenazocine poisoning
- Accidental phenoperidine overdose
- Accidental phenoperidine poisoning
- Accidental poisoning by pentazocine
- Accidental poisoning by pethidine
- Acetaminophen and/or dextropropoxyphene overdose
- Acetaminophen and/or dextropropoxyphene poisoning
- Buprenorphine overdose
- Buprenorphine poisoning
- Dextromoramide overdose
- Dextromoramide poisoning
- Dextropropoxyphene overdose
- Dextropropoxyphene poisoning
- Dipipanone overdose
- Dipipanone poisoning
- Levorphanol overdose
- Levorphanol poisoning
- Meperidine analog overdose
- Meperidine analog poisoning
- Meperidine overdose
- Morphinan opioid overdose
- Nalbuphine overdose
- Nalbuphine poisoning
- Pentazocine overdose
- Phenazocine overdose
- Phenazocine poisoning
- Phenoperidine overdose
- Phenoperidine poisoning
- Poisoning by meperidine
- Poisoning by pentazocine
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 narcotics and psychodysleptics [hallucinogens] (T40). 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 2027, published by CMS and the National Center for Health Statistics.
Instructional NotesGuidance
Instructions from the official ICD-10-CM Tabular List that apply to T40.491S: its own notes plus those printed at T40, block T36-T50, and Chapter 19. A note printed at a category, block or chapter applies to every code under it.
Includes
Further defines, or gives examples of, the content of the category.
- 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: the excluded code is never reported together with this one, unless the two conditions are unrelated.
- toxic reaction to local anesthesia in pregnancy (O29.3-)
Excludes2
Not included here: the excluded condition is not part of this code, but a patient may have both, so both codes may be reported.
Code First
The underlying condition named in the note is sequenced before this code.
Use Additional Code
Add a second code, after this one, to fully describe the condition.
- code to identify any retained foreign body, if applicable (Z18.-)
Notes
General instructions on how these codes are used.
- 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.
7th Character
Every code in the category takes a 7th character from the listed values, with the placeholder X filling any empty positions before it.
- The appropriate 7th character is to be added to each code from category T40
- Ainitial encounter
- Dsubsequent encounter
- Ssequela this code
Source: CMS ICD-10-CM Tabular List. How to read instructional notes.
Clinical ClassificationClinical
AHRQ’s CCSR groups this code into broader clinical categories.
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.
Code History & ChangesHistory
Replacement T40.491S replaces the following previously assigned code(s):
- T40.4X1S - Poisoning by oth synthetic narcotics, accidental, sequela
Questions About T40.491SOverview
Is T40.491S a billable code?
Yes. This is a billable ICD-10-CM code, specific enough to report poisoning by other synthetic narcotics, accidental (unintentional), sequela on HIPAA-covered claims from October 1, 2026 through September 30, 2027.
What does the 7th character S in T40.491S mean?
The final character S makes this a sequela code: it reports a lingering problem that remains after the poisoning by other synthetic narcotics, accidental (unintentional) itself has resolved, not the original event.
What MS-DRG does T40.491S group to?
When poisoning by other synthetic narcotics, accidental (unintentional), sequela is the principal diagnosis on an inpatient stay, it groups to MS-DRG 923, 922, with relative weights from 0.9980 to 1.6248 depending on complications. Higher weights mean higher Medicare reimbursement.
Is T40.491S 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 other synthetic narcotics, accidental (unintentional), sequela on inpatient claims. The code appears in the Poisoning by, adverse effect of and underdosing of drugs, medicaments and biological substances (T36-T50) range of the CMS exempt list.
Can T40.491S be reported with a code from O29.3?
Not as a rule. The Excludes1 note at block T36-T50, which applies to T40.491S, lists "toxic reaction to local anesthesia in pregnancy (O29.3-)". An Excludes1 note means the excluded code is never reported together with this one; the only exception is when the two conditions are unrelated to each other (Official Guidelines, Section I.A.12.a).
