Diagnostic agents are chemical substances used to reveal, pinpoint, and define pathological processes. The main types are X-ray contrast preparations, radioactive isotopes, and dyes. X-ray contrast agents make organs visible on scans by absorbing X-rays differently than tissues. They are introduced directly into organs or orally/intravenously. Diagnostic agents must be harmless, mix well with body fluids, accumulate selectively in organs, and eliminate completely from the body.

1. DIAGNOSTIC
AGENTS

2. DIAGNOSTIC AGENTS
Chemical substances used to revcal, pinpoint, and define the localization of a
pathological process.
The principal diagnostic agcnts are X-ray-contrast preparations, radioactive
isotopes, and dyes.
X-ray-contrast preparations are substances that possess the property of absorbing
and retaining X-radiation more weakly or more strongly than the tissues of the body;
introduction of these substances into the hollow organs makes it possible under X-
ray examination to get an idea of the configuration of the organ, its volume, the
character of its inner surfaces, and the presence of pathological changes.

3. DIAGNOSTIC AGENTS
Uscd as X-ray-contrast diagnostic agents are gascous substances (air, oxygen,
nitrous oxide, carbon dioxide), which absorb X-rays more
weakly than do body
tissues; fluid substances, such as
iodine-containing preparations in the form of
aqueous (Diodrast, Urokon Sodium, Sergosin) and oily (propyliodone) solutions or
suspensions; and substances administcred orally in the form of powders and
suspensions (Chlografin).
An aqueous suspension of barium sulfate is used for X-ray examination of the
gastrointestinal tract.
X-ray-contrast agents are introduced directly into the organ to be examined (for the
esophagus, stomach, intestine, bronchi, uterus, heart), orally or intravenously in
examining the liver, bilc ducts, and kidneys, or intraarterially in contrast
examination of the blood vessels (angiography) and heart.

4. DIAGNOSTIC AGENTS
Diagnostic agents are used in doses that are harmless to the body; they
are isotonic in relation to the body fluids and mix well with them,
accumulating selectively in the
readily and completely eliminated from the body in unaltered form.
ropriate organs, and they are

5. Contrast media/ Radiopaque agents
1. Water soluble contrast media: this may contain pharmaceutical
buffer like phosphates or citrate buffer and a sequestering agents.
they are mainly used for Urography, angiography.
2. Water insoluble contrast media: they are prepared as suspensions
and mainly used cholecystography, myelography.

6. DIAGNOSTIC AGENTS
Propyliodone
trade name: Dionosil
It is white crystalline powder
Odourless
Very slightly soluble in water
When heated with conc. Sulphuric acid, violet vapour of iodine is evolved.

7. Topanoic Acid
It is a white or creamy coloured powder which is odourless and almost tasteless
When it is heated with, violet vapours ofiodine is produced.
Duc to the prescnce of aromatic primary amino group, it undergoes diazotisation
and coupling reaction to give deep orange red ppt.
used in cholecystography

8. Sulfobromophthalein
It is a white crystalline powdcr which is odorless and has a bitter taste
It is soluble in water and practically insoluble in alcohol.
Stability and storage:
It is hygroscopic and hence is stored in tightly closed containers.
Uses:
It is used to test-the functional capacity of liver particularly its reticuloendothelial
cclls.
Dosage form: injection

9. Indigotindisulfonate
It is indoline-5-sulphonate derivative
It is dusky, purplish blue powder or blue granule with a coppery lustre
It is sparingly soluble in water
It is affected by light
Uses:
It is used to test kidney function
To localize urcteral orifices during ureteral catheterization and cystoscopy
Dosage form: injection

10. Evans Blue
It is an azo dye that has a very high affinity for serum albumin. Because ofthis, it can be
useful in physiology in estimating the proportion of body water contained in blood
plasma.
It is green or bluish green powder
Odorless
Soluble in water
Stability and storage:
It is hygroscopic and hence is stored in tightly closed containers.
Dosage form: injection

11. Congo Red
It is a secondary diazo dye. In biochemistry and histology, congo red is used to stain
microscopic preparates, especially as a cytoplasm and erythrocyte stain.
Apple-green birefringence of Congo red-stained preparates under polarized light is
ndicative ot the presencc of amyloid fibrils.
Additionally, congo red is used in microbiological epidemiology to rapidly identify the
prescncc of virulcnt serotype 2a Shigellaflexneri, whecre the dye binds the bacterium's
unique lipopolysaccharide structure.
It is dark red or reddish brown povwder and is odorless. It is soluble in water.
lt decomposes on exposure to fumes of mineral acids.
Dosage form: injection

12. Fluorescein Sodium
It is used extensively as a
diagnostic tool in the field of ophthalmology, where topical
fluorescein is used in the diagnosis of corneal abrasions, corneal ulcers, and herpetic
corneal infections. Intravenous or oral fluorescein is used in fluorescein angiography in
research and to diagnose and categorize vascular disorders in legs, including retinal
discase macular degeneration, diabctic retinopathy, inflammatory intraocular conditions,
and intraocular tumors, and increasingly during surgery for brain tumors.
It is orange red powder which is odorless and tasteless
Freely soluble in water
Stability and storage:
It is hygroscopic and hence is stored in tightly closed containers.