2026 ICD-10-CM Diagnosis Code T41.0X5AAdverse effect of inhaled anesthetics, initial encounter
T41.0X5A is a billable ICD-10-CM diagnosis code for adverse effect of inhaled anesthetics, initial encounter. The 7th character A marks it as an initial encounter code, used while the patient is receiving active treatment. It is valid on HIPAA claims for fiscal year 2026 (October 1, 2025 through September 30, 2026) and groups to MS-DRG 917 through 918. The code is not accepted as a principal diagnosis by the Medicare Code Editor. In AHRQ's Clinical Classifications Software (CCSR), this diagnosis falls under Adverse effects of drugs and medicaments, initial encounter; and Inhalant-related disorders.
Code Identity
Code Classification
Code EditsBilling
Medicare Code Editor checks that affect claim validity for T41.0X5A.
Approximate SynonymsGuidance
Alternate terms and clinical phrases that map to this code.
- Acute megaloblastic anemia
- Acute megaloblastic anemia caused by nitrous oxide
- Adverse reaction to inhaled anesthetic with ether structure
- Adverse reaction to nitrous oxide
- Chemical pneumonitis caused by anesthesia
- Desflurane adverse reaction
- Drug-induced apnea
- Drug-induced hepatitis
- Enflurane adverse reaction
- Enflurane hepatitis
- Enflurane poisoning
- Ether apnea
- Halothane adverse reaction
- Halothane hepatitis
- Halothane shakes
- Inhalational anesthetics adverse reaction
- Isoflurane adverse reaction
- Megaloblastic anemia caused by drugs
- Poisoning by halothane
- Trichloroethylene adverse reaction
Coding GuidelinesGuidance
When coding an adverse effect of a drug that has been correctly prescribed and properly administered, assign the appropriate code for the nature of the adverse effect followed by the appropriate code for the adverse effect of the drug.
The appropriate 7th character is to be added to each code from block Poisoning by, adverse effect of and underdosing of anesthetics and therapeutic gases (T41). 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
Enflurane
an extremely stable inhalation anesthetic that allows rapid adjustments of anesthesia depth with little change in pulse or respiratory rate.Halothane
a nonflammable, halogenated, hydrocarbon anesthetic that provides relatively rapid induction with little or no excitement. analgesia may not be adequate. nitrous oxide is often given concomitantly. because halothane may not produce sufficient muscle relaxation, supplemental neuromuscular blocking agents may be required. (from ama drug evaluations annual, 1994, p178)Isoflurane
a stable, non-explosive inhalation anesthetic, relatively free from significant side effects.Methoxyflurane
an inhalation anesthetic. currently, methoxyflurane is rarely used for surgical, obstetric, or dental anesthesia. if so employed, it should be administered with nitrous oxide to achieve a relatively light level of anesthesia, and a neuromuscular blocking agent given concurrently to obtain the desired degree of muscular relaxation. (from ama drug evaluations annual, 1994, p180)
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
Drug Reactions
Most of the time, medicines make our lives better. They reduce aches and pains, fight infections, and control problems such as high blood pressure or diabetes. But medicines can also cause unwanted reactions, such as drug interactions, side effects, and allergies.
The full article covers:
- What is a drug interaction?
- What are side effects?
- What are drug allergies?
- How can I stay safe when taking medicines?
Read the full article at MedlinePlus
Courtesy of MedlinePlus, a service of the U.S. National Library of Medicine.
Convert T41.0X5A to ICD-9-CMHistory
The closest ICD-9-CM equivalents under the General Equivalence Mappings.
Code HistoryHistory
Questions About T41.0X5AOverview
Is T41.0X5A (Adverse effect of inhaled anesthetics) a billable code?
Yes. This is a billable ICD-10-CM code, specific enough to report adverse effect of inhaled anesthetics, initial encounter on HIPAA-covered claims from October 1, 2025 through September 30, 2026.
What does the 7th character A in T41.0X5A mean?
The final character A marks the initial encounter: use it while the patient is receiving active treatment for adverse effect of inhaled anesthetics, such as an emergency visit or first evaluation.
What MS-DRG does T41.0X5A group to?
On inpatient claims, adverse effect of inhaled anesthetics, initial encounter maps to MS-DRG 917, 918, with relative weights from 0.8571 to 1.5684 depending on complications. Higher weights mean higher Medicare reimbursement.
Can T41.0X5A be a principal diagnosis?
No. The Medicare Code Editor rejects this code as a principal diagnosis because adverse effect of inhaled anesthetics, initial encounter describes a circumstance that influences health status rather than a current illness. Report it as a secondary diagnosis.
What is the ICD-9 equivalent of T41.0X5A?
Under the General Equivalence Mappings, adverse effect of inhaled anesthetics, initial encounter converts to ICD-9-CM 995.22 (adv eff anesthesia NOS) and E938.2 (adv eff gas anesthet NEC). 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.
