Iohexol - How It Works
Clinical pharmacology details from the US FDA-approved label: how Iohexol works in your body, how it's absorbed, how long it stays active, and how it's eliminated.
Mechanism of Action
12.1 Mechanism of Action The iodine atoms in iohexol provide attenuation of X-rays in direct proportion to the concentration of iohexol. Since concentration changes over time, iohexol provides time-dependent image contrast which may assist in visualizing body structures.
12 CLINICAL PHARMACOLOGY 12.1 Mechanism of Action The iodine atoms in iohexol provide attenuation of X-rays in direct proportion to the concentration of iohexol.
Since concentration changes over time, iohexol provides time-dependent image contrast which may assist in visualizing body structures.
12.2 Pharmacodynamics Intrathecal Administration The initial concentration and volume of the contrast medium, in conjunction with patient manipulation and the volume of cerebrospinal fluid (CSF) into which the contrast medium is placed, will determine the extent of the contrast that can be achieved.
Following intrathecal injection in conventional radiography, OMNIPAQUE 180 mg iodine/mL, 240 mg iodine/mL, and 300 mg iodine/mL will continue to provide contrast for at least 30 minutes.
Slow diffusion of iohexol takes place throughout the CSF with subsequent absorption into the bloodstream.
At approximately 1 hour following injection, contrast will no longer be sufficient for conventional myelography.
After administration into the lumbar subarachnoid space, computerized tomography shows the presence of contrast medium in the thoracic region in about 1 hour, in the cervical region in about 2 hours, and in the basal cisterns in 3 to 4 hours.
Intravenous or Intra-arterial Administration Following intravenous or intra-arterial administration of OMNIPAQUE, the degree of contrast enhancement is directly related to the iodine concentration of an administered dose; peak iodine blood concentrations occur immediately (15 seconds to 120 seconds) following rapid intravenous injection.
The time to maximum contrast enhancement can vary, depending on the organ, from the time that peak blood iodine concentrations are reached to one hour after intravenous bolus administration.
When a delay between peak blood iodine concentrations and peak contrast is present, it suggests that radiographic contrast enhancement is at least in part dependent on the accumulation of iodine containing agent within the lesion and outside the blood pool.
Oral Administration Orally administered OMNIPAQUE produces visualization of the gastrointestinal tract.
Less than 1% of orally administered iohexol is recovered in the urine, suggesting minimal amounts are absorbed from the normal gastrointestinal tract.
This amount may increase in the presence of bowel perforation or bowel obstruction.
Intraarticular Administration Visualization of the joint spaces can be accomplished by direct injection of contrast medium.
For intraarticular cavities, the injected iohexol is absorbed into the surrounding tissue and subsequently absorbed into systemic circulation.
Body Cavity Administration For most body cavities, the injected iohexol is absorbed into the surrounding tissue and subsequently absorbed into systemic circulation.
Examinations of the uterus (hysterosalpingography) and bladder (voiding cystourethrography) involve the almost immediate drainage of contrast medium from the cavity upon conclusion of the radiographic procedure.
12.3 Pharmacokinetics Following the intravenous administration of iohexol (between 500 mg iodine/kg to 1,500 mg iodine/kg) to 16 adult subjects, apparent first-order terminal elimination half-life was 12.6 hours and total body clearance was 131 (98 to 165) mL/min.
Clearance was not dose dependent.
Absorption As evidenced by the amount recovered in urine, <1% of orally administered iohexol is absorbed from the normal gastrointestinal tract.
Pharmacokinetics
12.3 Pharmacokinetics Following the intravenous administration of iohexol (between 500 mg iodine/kg to 1,500 mg iodine/kg) to 16 adult subjects, apparent first-order terminal elimination half-life was 12.6 hours and total body clearance was 131 (98 to 165) mL/min. Clearance was not dose dependent. Absorption As evidenced by the amount recovered in urine, <1% of orally administered iohexol is absorbed from the normal gastrointestinal tract. This amount may increase in the presence of bowel perforation or bowel obstruction. Distribution In 16 adult subjects (receiving between 500 mg iodine/kg to 1,500 mg iodine/kg intravenous iohexol) the plasma volume of distribution was165 (108 to 219) mL/kg. In five adult patients receiving 16 mL to 18 mL of OMNIPAQUE (180 mg iodine/mL) by lumbar intrathecal injection the plasma volume of distribution was 559 (350 to 849) mL/kg. Elimination Metabolism No significant metabolism, deiodination or biotransformation occurs. Excretion Following intravenous, intra-arterial or intrathecal administration, iohexol is excreted unchanged by glomerular filtration. Approximately 90% of the intravenously injected iohexol dose is excreted within the first 24 hours. Following intravenous or intraarterial administration, peak urine concentration occurs in the first hour after injection.