2026 ICD-10-CM Diagnosis Code T40.2X5AAdverse effect of other opioids, initial encounter
T40.2X5A is a billable ICD-10-CM diagnosis code for adverse effect of other opioids, 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 Opioid-related disorders.
Code Identity
Code Classification
Code EditsBilling
Medicare Code Editor checks that affect claim validity for T40.2X5A.
Approximate SynonymsGuidance
Alternate terms and clinical phrases that map to this code.
- Codeine adverse reaction
- Decreased respiratory function
- Diamorphine adverse reaction
- Dihydrocodeine adverse reaction
- Drug-induced constipation
- Morphinan opioid adverse reaction
- Morphine adverse reaction
- Opioid analgesic adverse reaction
- Pruritus caused by drug
- Pruritus caused by opioid
- Respiratory depression caused by opioid
- Therapeutic opioid induced constipation
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 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 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
Codeine
an opioid analgesic related to morphine but with less potent analgesic properties and mild sedative effects. it also acts centrally to suppress cough.Dextrorphan
dextro form of levorphanol. it acts as a noncompetitive nmda receptor antagonist, among other effects, and has been proposed as a neuroprotective agent. it is also a metabolite of dextromethorphan.Ethylmorphine
a narcotic analgesic and antitussive. it is metabolized in the liver by ethylmorphine-n-demethylase and used as an indicator of liver function.Ethylmorphine-N-Demethylase
a drug-metabolizing enzyme of the hepatic microsomal oxidase system which catalyzes the oxidation of the n-methyl group of ethylmorphine with the formation of formaldehyde.Etorphine
a narcotic analgesic morphinan used as a sedative in veterinary practice.Hydrocodone
narcotic analgesic related to codeine, but more potent and more addicting by weight. it is used also as cough suppressant.Hydromorphone
an opioid analgesic made from morphine and used mainly as an analgesic. it has a shorter duration of action than morphine.Glucuronosyltransferase
a family of enzymes accepting a wide range of substrates, including phenols, alcohols, amines, and fatty acids. they function as drug-metabolizing enzymes that catalyze the conjugation of udpglucuronic acid to a variety of endogenous and exogenous compounds. ec 2.4.1.17.Morphine
the principal alkaloid in opium and the prototype opiate analgesic and narcotic. morphine has widespread effects in the central nervous system and on smooth muscle.Morphine Dependence
strong dependence, both physiological and emotional, upon morphine.Morphine Derivatives
analogs or derivatives of morphine.Receptors, Opioid, mu
a class of opioid receptors recognized by its pharmacological profile. mu opioid receptors bind, in decreasing order of affinity, endorphins, dynorphins, met-enkephalin, and leu-enkephalin. they have also been shown to be molecular receptors for morphine.Oxycodone
a semisynthetic derivative of codeine.Oxymorphone
an opioid analgesic with actions and uses similar to those of morphine, apart from an absence of cough suppressant activity. it is used in the treatment of moderate to severe pain, including pain in obstetrics. it may also be used as an adjunct to anesthesia. (from martindale, the extra pharmacopoeia, 30th ed, p1092)Thebaine
a drug that is derived from opium, which contains from 0.3-1.5% thebaine depending on its origin. it produces strychnine-like convulsions rather than narcosis. it may be habit-forming and is a controlled substance (opiate) listed in the u.s. code of federal regulations, title 21 part 1308.12 (1985). (from merck index, 11th ed)
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 T40.2X5A to ICD-9-CMHistory
The closest ICD-9-CM equivalents under the General Equivalence Mappings.
Code HistoryHistory
Questions About T40.2X5AOverview
Is T40.2X5A (Adverse effect of other opioids) a billable code?
Yes. This is a billable ICD-10-CM code, specific enough to report adverse effect of other opioids, initial encounter on HIPAA-covered claims from October 1, 2025 through September 30, 2026.
What does the 7th character A in T40.2X5A mean?
The final character A marks the initial encounter: use it while the patient is receiving active treatment for adverse effect of other opioids, such as an emergency visit or first evaluation.
What MS-DRG does T40.2X5A group to?
On inpatient claims, adverse effect of other opioids, 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 T40.2X5A be a principal diagnosis?
No. The Medicare Code Editor rejects this code as a principal diagnosis because adverse effect of other opioids, 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 T40.2X5A?
Under the General Equivalence Mappings, adverse effect of other opioids, initial encounter converts to ICD-9-CM 995.29 (adv eff med/biol NEC/NOS) and E935.2 (adv eff opiates). 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.
