Pharmacokinetics of iopamidol after intrathecal administration in humans

The kinetics of iopamidol, a new nonionic radiocontrast agent, were evaluated in 10 patients undergoing lumbar myelography. The doses of iopamidol administered intrathecally were 11 and 15 ml of a 200-mg iodine per ml solution in one and nine patients, respectively. Radiographs were made within 30 to 40 min and CTs were taken at about 1, 6, and 23 hr after iopamidol administration. The diagnostic quality and usefulness of the conventional and CT myelograms were considered excellent. In the lumbosacral subarachnoid space, the densitometry CT readings were maximal at 1 hr, whereas in the cervical subarachnoid space, peak CT values were reached at 6 hr. Plasma and urine samples were taken at frequent intervals up to 48 hr after the contrast agent was administered. Peak plasma levels of iopamidol were observed at 2.9 hr and were no longer detectable at 48 hr. The 48-hr urinary recovery for all patients averaged 66 ± 8% of the dose. In all but one patient, iopamidol was cleared almost completely from the CSF within 24 hr. Side effects after iopamidol administraition were transient and minor, and were not related to the CT readings or its systemic clearance.