2026 ICD-10-CM Diagnosis Code T40.5X5AAdverse effect of cocaine, initial encounter
T40.5X5A is a billable ICD-10-CM diagnosis code for adverse effect of cocaine, 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. Coders also document this condition as cocaine adverse reaction. In AHRQ's Clinical Classifications Software (CCSR), this diagnosis falls under Adverse effects of drugs and medicaments, initial encounter; and Stimulant-related disorders.
Code Identity
Code Classification
Code EditsBilling
Medicare Code Editor checks that affect claim validity for T40.5X5A.
Approximate SynonymsGuidance
Alternate terms and clinical phrases that map to this code.
- Cocaine 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 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
Cocaine
an alkaloid ester extracted from the leaves of plants including coca. it is a local anesthetic and vasoconstrictor and is clinically used for that purpose, particularly in the eye, ear, nose, and throat. it also has powerful central nervous system effects similar to the amphetamines and is a drug of abuse. cocaine, like amphetamines, acts by multiple mechanisms on brain catecholaminergic neurons; the mechanism of its reinforcing effects is thought to involve inhibition of dopamine uptake.Cocaine- and Amphetamine-Regulated Transcript Protein
neuropeptide that functions with neuropeptide y and leptin in the regulation of appetite. it also plays a role in neural development and is involved in the regulation of energy homeostasis and stress control.Cocaine Smoking
smoking of cocaine.Cocaine-Related Disorders
disorders related or resulting from use of cocaine.Crack Cocaine
the purified, alkaloidal, extra-potent form of cocaine. it is smoked (free-based), injected intravenously, and orally ingested. use of crack results in alterations in function of the cardiovascular system, the autonomic nervous system, the central nervous system, and the gastrointestinal system. the slang term crack was derived from the crackling sound made upon igniting of this form of cocaine for smoking.
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
Cocaine
Cocaine is a very addictive drug that is made from leaves of the coca plant found in South America. It is mostly available as an illegal drug that some people use to get high. In rare cases, it is also used as a prescription drug for for anesthesia during certain surgeries.
The full article covers:
- What is cocaine?
- How do people use cocaine?
- What are the short-term effects of cocaine?
- What are the long-term effects of cocaine?
- Can a person overdose on cocaine?
- What are the treatments for cocaine use disorder?
Read the full article at MedlinePlus
Courtesy of MedlinePlus, a service of the U.S. National Library of Medicine.
Convert T40.5X5A to ICD-9-CMHistory
The closest ICD-9-CM equivalents under the General Equivalence Mappings.
Code HistoryHistory
Questions About T40.5X5AOverview
Is T40.5X5A (Adverse effect of cocaine) a billable code?
Yes. This is a billable ICD-10-CM code, specific enough to report adverse effect of cocaine, initial encounter on HIPAA-covered claims from October 1, 2025 through September 30, 2026.
What does the 7th character A in T40.5X5A mean?
The final character A marks the initial encounter: use it while the patient is receiving active treatment for adverse effect of cocaine, such as an emergency visit or first evaluation.
What MS-DRG does T40.5X5A group to?
On inpatient claims, adverse effect of cocaine, 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 T40.5X5A be a principal diagnosis?
No. The Medicare Code Editor rejects this code as a principal diagnosis because adverse effect of cocaine, 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 T40.5X5A?
Under the General Equivalence Mappings, adverse effect of cocaine, initial encounter converts to ICD-9-CM 995.29 (adv eff med/biol NEC/NOS) and E939.7 (adv eff psychostimulants). 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.
