Changes in version 0.4.0 (2026-05-27)                  

New features

  - Added support for retrieving active and historical RxNorm product
    concepts in product discovery workflows, including
    products_for_ingredients() and related search helpers.
  - Added concept_status support to allow users to request active
    concepts only or active plus historical RxNorm concepts, where
    supported.
  - Added exclude_products_with_ingredients(), a product-level filtering
    helper for removing RxNorm products that contain user-specified
    ingredients.
  - exclude_products_with_ingredients() supports fixed-dose combination
    products represented with semicolon-delimited ingredient names or
    RxCUIs, such as "atenolol; chlorthalidone".
  - Added safer internal handling for historical concept verification
    and lookups, reducing failures when RxNorm returns incomplete,
    empty, or unexpected API responses.

Improvements

  - Improved retrieval of clinical product attributes for historical
    RxCUIs by attempting to recover dose form, dose form group, route,
    ingredient count, and ingredient metadata when available.
  - Improved route filtering workflows for products that include
    historical RxNorm concepts.
  - Improved fixed-dose combination formatting in
    get_clinical_attributes(). Ingredient fields such as
    ingredient_rxcui, ingredient_name, and ingredient_tty now use
    semicolon-delimited strings instead of pseudo-vector strings.
  - Improved consistency of product-level ingredient metadata to support
    cleaner downstream joins and filtering.
  - Improved reuse of cached API responses in product discovery,
    historical concept lookup, and clinical attribute workflows to
    reduce repeated calls to the RxNorm and RxClass APIs.
  - Added or improved progress reporting for longer-running product
    discovery workflows, including API retrieval steps where
    appropriate.
  - Updated route-specific vignette example datasets so package
    vignettes do not rely on live API calls during package checks.
  - Updated vignette example datasets to avoid duplicated .x / .y join
    columns and to use current, singular column naming conventions.
  - Updated README examples and package vignettes to reflect current
    function behavior, argument names, output columns, and recommended
    workflows.
  - Improved internal helper functions for normalizing product
    ingredient fields and handling fixed-dose combination products.

Bug fixes

  - Fixed issues where historical or obsolete RxCUIs could return
    incomplete clinical attributes and be unintentionally dropped from
    route-filtered workflows.
  - Fixed cases where historical product concepts could produce
    incorrect or inflated ingredient counts.
  - Fixed validation and test coverage for concept_status arguments.
  - Fixed issues arising from incomplete or malformed historical concept
    lookups.
  - Fixed vignette data-generation issues that could create unexpected
    NA rows in pre-built example datasets.
  - Fixed CRAN submission issues related to API name formatting, web
    references, and package citation handling.

Documentation

  - Updated package documentation to describe active and historical
    RxNorm concept support.
  - Updated documentation for product discovery, clinical attribute
    retrieval, route filtering, and fixed-dose combination handling.
  - Updated NEWS, README, vignettes, and CRAN-facing metadata for
    the 0.4.0 release.
  - Updated package citation handling to avoid errors when the package
    is not installed.

                        Changes in version 0.3.0                        

  - Removed the experimental set_backend() helper. rxref currently uses
    the RxNorm/RxClass APIs directly.