Absorption of metrizamide from cereb rospinal fluid to blood: pharmacokinetics in humans.

The rate of transfer of contrast agents from cerebrospinal fluid to blood is of clinical importance in radiological examinations of the subarachnoid space. Metrizamide, a potential contrast medium, was injected intrathecally to humans and serum levels at different times after injection were measured. A one-compartment open model was found to apply to the data. Considerable individual variations were found, but the mean absorption rate constant indicated that more than 50% of the absorbed dose had disappeared from the cerebrospinal fluid 0.75 hr after injection. TLC of the fraction excreted in the urine showed that metrizamide was not metabolized in the body.