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Clinical data
Synonyms 3-acetamido-2,4,6-triiodo-5-(N-methylacetamido)-N-[(3R,4R,5S,6R)-2,4,5-trihydroxy-6-(hydroxymethyl)oxan-3-yl]benzamide
AHFS/ Micromedex Detailed Consumer Information
ATC code
CAS Number
PubChem CID
ECHA InfoCard 100.045.872
Chemical and physical data
Formula C18H22I3N3O8
Molar mass 789.10 g/mol
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Metrizamide is a nonionic radiopaque contrast agent.
A density gradient medium for the centrifugation of biological particles.

Historically Metrizamide replaced Pantopaque as the contrast agent of choice for Myelography (an X-ray study of the spine now largely replaced by MRI). The radio opacity characteristics are such that finer detail is displayed with Metrizamide as well as the advantage of reabsorption from spinal fluid and excretion from the body.

Both agents are administered by spinal tap (lumbar puncture - LP or cisternal puncture at the cervicocranial junction). The human patient is rolled from the lateral decubitus (lying on the side) to prone. Ankles are strapped to the end of a hard X-ray, CT, or MRI table. To obtain images of the cervical region the patient is then carefully tilted cephalad (toward the head) so contrast agent (particularly Pantopaque) can enter the neck region. Care is given to prevent spilling dye into the posterior fossa (back of the head) or to enter the cranial cavity in general. This speaks to the inability to remove the heavier or more viscous Pantopaque without aspirating it with spinal fluid (CSF) through a lumbar puncture needle in the low back (sticking up vertically) or back of the neck. With Metrizamide the issue is that if entering the cranial cavity and high dose exposure to the blood brain barrier, side effects are more likely encountered. Issues related to absorption into the general circulation are also encountered.

Side Effects:

  • Headache
  • Nausea
  • Vomiting
  • Mass effect, herniation and major Central Nervous System complications including spinal cord compression
  • Seizures
  • Muscle rigidity and dystonic reaction