T37.8X5A Adverse effect of other specified systemic anti-infectives and antiparasitics, initial encounter

ICD-10-CM T37.8X5A: Adverse effect of other specified systemic anti-infectives and antiparasitics, initial encounter

ICD-10-CM code T37.8X5A is labeled as the adverse effect of other specified systemic anti-infectives and antiparasitics, initial encounter. The code appears in official terminology resources and payer billing articles. Antimicrobial therapies are associated with variable harms, including allergies and serious conditions, with about half of these adverse effects starting after community prescribing. 2 5 1 3 4

Plain-language overview

The official label for T37.8X5A is adverse effect of other specified systemic anti-infectives and antiparasitics, initial encounter. This terminology is explicitly provided by official electronic vocabulary sources. 2 5

What this code represents

The code T37.8X5A is listed alongside T37.8X5S, which is labeled as a sequela. This establishes a direct relationship between the two codes within the same ICD-10-CM concept family. 2

The T37.8X5A code is included in Centers for Medicare and Medicaid Services billing and coding articles for allergy testing and RAST type tests. This demonstrates its use in official payer documentation contexts. 3 4

Clinical context

Antimicrobial therapies are associated with variable harms that include allergies, short-term harms, and serious harms. Information on these adverse effects is often abbreviated or simplified in drug reference materials. 1

About half of adverse effects from antimicrobials start after taking these medications in community settings. These community-prescribed antimicrobials are often prescribed by non-family physician specialists for complex medical problems. 1

Documentation considerations

Clearly identifying the effects of any one drug is difficult because patients who are more ill have often taken many drugs. These patients are more likely to seek help from health care providers and be treated. 1

What the sources add

While clinical literature details specific antimicrobial harms like Clostridium difficile infections, official coding sources provide the exact T37.8X5A label. The payer articles list the code without detailing the specific medications involved. 1 2 3 4

The Centers for Medicare and Medicaid Services articles present T37.8X5A in the context of allergy testing and RAST type tests. The National Cancer Institute EVS Explore provides the exact code label and an order number. 3 4 5

Sources

1. Update on the adverse effects of antimicrobial therapies in community practice — pmc.ncbi.nlm.nih.gov; accessed 2026-07-25.
2. EVS Explore — evsexplore.semantics.cancer.gov; accessed 2026-07-25.
3. Article - Billing and Coding: Allergy Testing (A57531) — cms.gov; accessed 2026-07-25.
4. Article - Billing and Coding: RAST Type Tests (A57043) — cms.gov; accessed 2026-07-25.
5. EVS Explore — evsexplore.semantics.cancer.gov; accessed 2026-07-25.