Diagnostic agents are the substances used to examine the body in order to detect impairment of its normal functions. Usually, these agents find no other use in medicine.

Diagnostic agents are divided according to the use as

  • drugs used as X-ray contrast media
  • drugs used to test organ functions
  • drugs used to determine blood volume and haemopoietic function and
  • drugs used for miscellaneous agents.


They are classified according to their test functionalities as

  1. Gall bladder function, cholecystography, and cholangiography: eg. Iocetamic acid, Iodipamide, Tyropanoate sodium.
  2. Gastric function: eg. Pentagastrin, Congored.
  3. Liver function: eg. Indocyanine green.
  4. Ophthalmic diagnostic aid: eg. Fluorescein sodium.
  5. Pancreatic function: eg. Bentiromide.
  6. Intestinal function: eg. Barium sulfate, Xylose.
    • Radiological Contrast Media A) Heavy metals and salts: eg. i) Barium Sulphate (BaSO4) –
      • Low systematic toxicity -Low water solubility –
      • Lack of osmotic activity –
      • Used for examination of GIT -Used as suspension or thick cream
      • Orally or through rectal route – sod.citrate is added to stabilize preparation
      • Sorbitol added to enhance the function
  7. Kidney function: eg. Aminohippurate sodium, Indigotin disulfonate, Phenolsulphophthalein.
  8. Lymphatic system: eg. Isosulfan blue.
  9. Bronchial airway hyperacidity: eg. Methacholine.
  10. Drug – hypersensitivity: eg. Benzyl penicilloyl polylysine.
  11. Drugs used in X-ray contrast medium: eg. Diatriazoic acid, Iocetamic acid, Iothalamic acid, Propyliodone.
  12. Miscellaneous: eg. Erythrosin sodium, Evans blue.

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