2026 ICD-10-CM Diagnosis Code T42.8X2APoisoning by antiparkinsonism drugs and other central muscle-tone depressants, intentional self-harm, initial encounter
T42.8X2A is a billable ICD-10-CM diagnosis code for poisoning by antiparkinsonism drugs and other central muscle-tone depressants, intentional self-harm, 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. In AHRQ's Clinical Classifications Software (CCSR), this diagnosis falls under External cause codes: intent of injury, self-harm; External cause codes: poisoning by drug; and Poisoning by drugs, initial encounter.
Code Identity
Code Classification
Approximate SynonymsGuidance
Alternate terms and clinical phrases that map to this code.
- Amantadine overdose
- Antiviral drug overdose
- Baclofen overdose
- Bromocriptine overdose
- Bromocriptine poisoning
- Intentional amantadine overdose
- Intentional amantadine poisoning
- Intentional baclofen overdose
- Intentional bromocriptine overdose
- Intentional bromocriptine poisoning
- Intentional ergot alkaloid overdose
- Intentional ergot alkaloid poisoning
- Intentional levodopa overdose
- Intentional levodopa poisoning
- Intentional lysuride overdose
- Intentional lysuride poisoning
- Intentional selegiline overdose
- Intentional selegiline poisoning
- Levodopa overdose
- Lysuride overdose
- Lysuride poisoning
- Poisoning by amantadine
- Poisoning by levodopa
- Selegiline overdose
- Selegiline poisoning
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
Amantadine
an antiviral that is used in the prophylactic or symptomatic treatment of influenza a. it is also used as an antiparkinsonian agent, to treat extrapyramidal reactions, and for postherpetic neuralgia. the mechanisms of its effects in movement disorders are not well understood but probably reflect an increase in synthesis and release of dopamine, with perhaps some inhibition of dopamine uptake.Baclofen
a gamma-aminobutyric acid derivative that is a specific agonist of gaba-b receptors. it is used in the treatment of muscle spasticity, especially that due to spinal cord injuries. its therapeutic effects result from actions at spinal and supraspinal sites, generally the reduction of excitatory transmission.Receptors, GABA-B
a subset of gaba receptors that signal through their interaction with heterotrimeric g-proteins.Benserazide
an inhibitor of dopa decarboxylase that does not enter the central nervous system. it is often given with levodopa in the treatment of parkinsonism to prevent the conversion of levodopa to dopamine in the periphery, thereby increasing the amount that reaches the central nervous system and reducing the required dose. it has no antiparkinson actions when given alone.Bromocriptine
a semisynthetic ergotamine alkaloid that is a dopamine d2 agonist. it suppresses prolactin secretion.Cabergoline
an ergoline derivative and dopamine d2-agonist that inhibits prolactin secretion. it is used in the management of hyperprolactinemia, and to suppress lactation following childbirth for medical reasons. cabergoline is also used in the management of parkinson disease.Carisoprodol
a centrally acting skeletal muscle relaxant whose mechanism of action is not completely understood but may be related to its sedative actions. it is used as an adjunct in the symptomatic treatment of musculoskeletal conditions associated with painful muscle spasm. (from martindale, the extra pharmacopoeia, 30th ed, p1202)Chlorphenesin
a centrally acting muscle relaxant. its mode of action is unknown. (from martindale, the extra pharmacopoeia, 30th ed, p1203)Chlorzoxazone
a centrally acting central muscle relaxant with sedative properties. it is claimed to inhibit muscle spasm by exerting an effect primarily at the level of the spinal cord and subcortical areas of the brain. (from martindale, the extra pharmacopoea, 30th ed, p1202)Dantrolene
skeletal muscle relaxant that acts by interfering with excitation-contraction coupling in the muscle fiber. it is used in spasticity and other neuromuscular abnormalities. although the mechanism of action is probably not central, dantrolene is usually grouped with the central muscle relaxants.Levodopa
the naturally occurring form of dihydroxyphenylalanine and the immediate precursor of dopamine. unlike dopamine itself, it can be taken orally and crosses the blood-brain barrier. it is rapidly taken up by dopaminergic neurons and converted to dopamine. it is used for the treatment of parkinsonian disorders and is usually given with agents that inhibit its conversion to dopamine outside of the central nervous system.Lisuride
an ergot derivative that acts as an agonist at dopamine d2 receptors (dopamine agonists). it may also act as an antagonist at dopamine d1 receptors, and as an agonist at some serotonin receptors (serotonin receptor agonists).Mephenesin
a centrally acting muscle relaxant with a short duration of action.Metergoline
a dopamine agonist and serotonin antagonist. it has been used similarly to bromocriptine as a dopamine agonist and also for migraine disorders therapy.Methocarbamol
a centrally acting muscle relaxant whose mode of action has not been established. it is used as an adjunct in the symptomatic treatment of musculoskeletal conditions associated with painful muscle spasm. (from martindale, the extra pharmacopoeia, 30th ed, p1206)Pergolide
a long-acting dopamine agonist which has been used to treat parkinson disease and hyperprolactinemia but withdrawn from some markets due to potential for heart valve diseases.Piribedil
a dopamine d2 agonist. it is used in the treatment of parkinson disease, particularly for alleviation of tremor. it has also been used for circulatory disorders and in other applications as a d2 agonist.Selegiline
a selective, irreversible inhibitor of type b monoamine oxidase that is used for the treatment of newly diagnosed patients with parkinson disease, and for the treatment of depressive disorders. the compound without isomeric designation is deprenyl.Zoxazolamine
a uricosuric and muscle relaxant. zoxazolamine acts centrally as a muscle relaxant, but the mechanism of its action is not understood.
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
Poisoning
A poison is any substance that is harmful to your body. You might swallow it, inhale it, inject it, or absorb it through your skin. Any substance can be poisonous if too much is taken. Poisons can include:
Read the full article at MedlinePlus
Courtesy of MedlinePlus, a service of the U.S. National Library of Medicine.
Convert T42.8X2A to ICD-9-CMHistory
The closest ICD-9-CM equivalents under the General Equivalence Mappings.
Code HistoryHistory
Questions About T42.8X2AOverview
Is T42.8X2A a billable code?
Yes. This is a billable ICD-10-CM code, specific enough to report poisoning by antiparkinsonism drugs and other central muscle-tone depressants, intentional self-harm, initial encounter on HIPAA-covered claims from October 1, 2025 through September 30, 2026.
What does the 7th character A in T42.8X2A mean?
The final character A marks the initial encounter: use it while the patient is receiving active treatment for poisoning by antiparkinsonism drugs and other central muscle-tone depressants, intentional self-harm, such as an emergency visit or first evaluation.
What MS-DRG does T42.8X2A group to?
When poisoning by antiparkinsonism drugs and other central muscle-tone depressants, intentional self-harm, initial encounter is the principal diagnosis on an inpatient stay, it groups to MS-DRG 917, 918, with relative weights from 0.8571 to 1.5684 depending on complications. Higher weights mean higher Medicare reimbursement.
What is the ICD-9 equivalent of T42.8X2A?
Under the General Equivalence Mappings, poisoning by antiparkinsonism drugs and other central muscle-tone depressants, intentional self-harm, initial encounter converts to ICD-9-CM 966.4 (pois-anti-parkinson drug), 968.0 (pois-cns muscle depress), and E950.4 (poison-drug/medicin 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.
