2026 ICD-10-CM Diagnosis Code T37.3X5AAdverse effect of other antiprotozoal drugs, initial encounter
T37.3X5A is a billable ICD-10-CM diagnosis code for adverse effect of other antiprotozoal drugs, 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.
Code Identity
Code Classification
Code EditsBilling
Medicare Code Editor checks that affect claim validity for T37.3X5A.
Approximate SynonymsGuidance
Alternate terms and clinical phrases that map to this code.
- Adverse reaction to antimony and/or antimony compound
- Adverse reaction to diamidine
- Adverse reaction to dichloroacetamide
- Adverse reaction to emetine
- Antiprotozoal drug adverse reaction
- Atovaquone adverse reaction
- Diloxanide adverse reaction
- Nimorazole adverse reaction
- Nitroimidazole adverse reaction
- Pentamidine adverse reaction
- Sodium stibogluconate adverse reaction
- Tinidazole 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 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
Emetine
the principal alkaloid of ipecac, from the ground roots of uragoga (or cephaelis) ipecacuanha or u. acuminata, of the rubiaceae. it is used as an amebicide in many different preparations and may cause serious cardiac, hepatic, or renal damage and violent diarrhea and vomiting. emetine inhibits protein synthesis in eukaryotic cells but not prokaryotic cells.Glaucarubin
(1 beta,2 alpha,11 beta,12 alpha,15 beta(s))-11,20-epoxy-1,2,11,12-tetrahydroxy-15-(2-hydroxy-2-methyl-1-oxobutoxy)picras-3-en-16-one. a quassinoid (simaroubolide) from simaruba glauca, a tropical shrub. it has been used as an antiamebic agent and is found to be cytotoxic. it may be of use in cancer chemotherapy.Melarsoprol
arsenical used in trypanosomiases. it may cause fatal encephalopathy and other undesirable side effects.Misonidazole
a nitroimidazole that sensitizes normally radio-resistant hypoxic cells to radiation. it may also be directly cytotoxic to hypoxic cells and has been proposed as an antineoplastic.Nifurtimox
a nitrofuran thiazine that has been used against trypanosomiasis.Nimorazole
an antitrichomonal agent which is effective either topically or orally and whose urinary metabolites are also trichomonicidal.Ornidazole
a nitroimidazole antiprotozoal agent used in ameba and trichomonas infections. it is partially plasma-bound and also has radiation-sensitizing action.Pentamidine
antiprotozoal agent effective in trypanosomiasis, leishmaniasis, and some fungal infections; used in treatment of pneumocystis pneumonia in hiv-infected patients. it may cause diabetes mellitus, central nervous system damage, and other toxic effects.Tinidazole
a nitroimidazole alkylating agent that is used as an antitrichomonal agent against trichomonas vaginalis; entamoeba histolytica; and giardia lamblia infections. it also acts as an antibacterial agent for the treatment of bacterial vaginosis and anaerobic bacterial infections.
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 T37.3X5A to ICD-9-CMHistory
The closest ICD-9-CM equivalents under the General Equivalence Mappings.
Code HistoryHistory
Questions About T37.3X5AOverview
Is T37.3X5A (Adverse effect of other antiprotozoal drugs) a billable code?
Yes. This is a billable ICD-10-CM code, specific enough to report adverse effect of other antiprotozoal drugs, initial encounter on HIPAA-covered claims from October 1, 2025 through September 30, 2026.
What does the 7th character A in T37.3X5A mean?
The final character A marks the initial encounter: use it while the patient is receiving active treatment for adverse effect of other antiprotozoal drugs, such as an emergency visit or first evaluation.
What MS-DRG does T37.3X5A group to?
On inpatient claims, adverse effect of other antiprotozoal drugs, 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 T37.3X5A be a principal diagnosis?
No. The Medicare Code Editor rejects this code as a principal diagnosis because adverse effect of other antiprotozoal drugs, 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 T37.3X5A?
Under the General Equivalence Mappings, adverse effect of other antiprotozoal drugs, initial encounter converts to ICD-9-CM 995.29 (adv eff med/biol NEC/NOS) and E931.5 (adv eff antprotazoal 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.
