2026 ICD-10-CM Diagnosis Code T37.2X5SAdverse effect of antimalarials and drugs acting on other blood protozoa, sequela
T37.2X5S is a billable ICD-10-CM diagnosis code for adverse effect of antimalarials and drugs acting on other blood protozoa, 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 2026 (October 1, 2025 through September 30, 2026) and groups to MS-DRG 922 through 923. The code is not accepted as a principal diagnosis by the Medicare Code Editor and exempt from POA reporting. In AHRQ's Clinical Classifications Software (CCSR), this diagnosis falls under Poisoning/toxic effect/adverse effects/underdosing, sequela.
Code Identity
Code Classification
Code EditsBilling
Medicare Code Editor checks that affect claim validity for T37.2X5S.
Present on Admission (POA)Billing
T37.2X5S is exempt from POA reporting on inpatient claims to general acute care hospitals. Review other POA exempt codes.
Approximate SynonymsGuidance
Alternate terms and clinical phrases that map to this code.
- Adverse reaction to Cinchona alkaloid
- Adverse reaction to cycloguanil
- Adverse reaction to sulfadoxine and pyrimethamine
- Aminoquinoline antimalarial adverse reaction
- Amodiaquine adverse reaction
- Antimalarial drug adverse reaction
- Biguanide adverse reaction
- Biguanide antimalarial adverse reaction
- Bilateral toxic maculopathy
- Chloroquine adverse reaction
- Chloroquine myopathy
- Chloroquine retinopathy
- Halofantrine adverse reaction
- Hemolytic anemia caused by drugs
- Left toxic maculopathy
- Mefloquine adverse reaction
- Mepacrine adverse reaction
- Post-artesunate delayed hemolysis
- Primaquine adverse reaction
- Primaquine sensitivity anemia
- Proguanil adverse reaction
- Pruritus caused by antimalarial
- Pruritus caused by drug
- Pyrimethamine adverse reaction
- Quinine adverse reaction
- Quinine retinopathy
- Right toxic maculopathy
- Toxic maculopathy
- Toxic maculopathy of bilateral eyes caused by antimalarial drug
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 other systemic anti-infectives and antiparasitics (T37). 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
Amodiaquine
a 4-aminoquinoline compound with anti-inflammatory properties.Chloroquine
the prototypical antimalarial agent with a mechanism that is not well understood. it has also been used to treat rheumatoid arthritis, systemic lupus erythematosus, and in the systemic therapy of amebic liver abscesses.Cinchona
a genus of rubiaceous south american trees that yields the toxic cinchona alkaloids from their bark; quinine; quinidine; chinconine, cinchonidine and others are used to treat malaria and cardiac arrhythmias.Cinchona Alkaloids
alkaloids extracted from various species of cinchona.Eflornithine
an inhibitor of ornithine decarboxylase, the rate limiting enzyme of the polyamine biosynthetic pathway.Mefloquine
a phospholipid-interacting antimalarial drug (antimalarials). it is very effective against plasmodium falciparum with very few side effects.Primaquine
an aminoquinoline that is given by mouth to produce a radical cure and prevent relapse of vivax and ovale malarias following treatment with a blood schizontocide. it has also been used to prevent transmission of falciparum malaria by those returning to areas where there is a potential for re-introduction of malaria. adverse effects include anemias and gi disturbances. (from martindale, the extra pharmacopeia, 30th ed, p404)Proguanil
a biguanide compound which metabolizes in the body to form cycloguanil, an anti-malaria agent.Pyrimethamine
one of the folic acid antagonists that is used as an antimalarial or with a sulfonamide to treat toxoplasmosis.Quinacrine
an acridine derivative formerly widely used as an antimalarial but superseded by chloroquine in recent years. it has also been used as an anthelmintic and in the treatment of giardiasis and malignant effusions. it is used in cell biological experiments as an inhibitor of phospholipase a2.Quinacrine Mustard
nitrogen mustard analog of quinacrine used primarily as a stain in the studies of chromosomes and chromatin. fluoresces by reaction with nucleic acids in chromosomes.Quinine
an alkaloid derived from the bark of the cinchona tree. it is used as an antimalarial drug, and is the active ingredient in extracts of the cinchona that have been used for that purpose since before 1633. quinine is also a mild antipyretic and analgesic and has been used in common cold preparations for that purpose. it was used commonly and as a bitter and flavoring agent, and is still useful for the treatment of babesiosis. quinine is also useful in some muscular disorders, especially nocturnal leg cramps and myotonia congenita, because of its direct effects on muscle membrane and sodium channels. the mechanisms of its antimalarial effects are not well 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
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 T37.2X5S to ICD-9-CMHistory
The closest ICD-9-CM equivalents under the General Equivalence Mappings.
Code HistoryHistory
Questions About T37.2X5SOverview
Is T37.2X5S a billable code?
Yes. This is a billable ICD-10-CM code, specific enough to report adverse effect of antimalarials and drugs acting on other blood protozoa, sequela on HIPAA-covered claims from October 1, 2025 through September 30, 2026.
What does the 7th character S in T37.2X5S mean?
The final character S makes this a sequela code: it reports a lingering problem that remains after the adverse effect of antimalarials and drugs acting on other blood protozoa itself has resolved, not the original event.
What MS-DRG does T37.2X5S group to?
On inpatient claims, adverse effect of antimalarials and drugs acting on other blood protozoa, sequela maps to MS-DRG 922, 923, with relative weights from 1.0177 to 1.7494 depending on complications. Higher weights mean higher Medicare reimbursement.
Can T37.2X5S be a principal diagnosis?
No. The Medicare Code Editor rejects this code as a principal diagnosis because adverse effect of antimalarials and drugs acting on other blood protozoa, sequela describes a circumstance that influences health status rather than a current illness. Report it as a secondary diagnosis.
Is T37.2X5S 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 adverse effect of antimalarials and drugs acting on other blood protozoa, sequela on inpatient claims.
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.
