Absorption after subarachnoid and subdural administration of iohexol, 51Cr-EDTA, and 125I-albumin to rabbits.

The absorption of the nonionic contrast medium iohexol, the clearance tracer 51Cr-ethylenediaminetetraacetic acid, and the blood-pool marker 125I-human serum albumin was studied after subarachnoid and subdural injection in rabbits. Subdural deposition of the contrast medium and 51Cr-ethylenediaminetetraacetic acid resulted in a faster absorption rate and higher achieved blood levels than a subarachnoid injection of the two substances, where a slow absorption to lower blood concentrations was observed. No significant differences in absorption rate could be shown after subdural and subarachnoid administration of iodine-labelled albumin. The excretion of iohexol was observed for 1 week after the intrathecal injection. For both the subdural and subarachnoid depositions, about 83% of the injected iohexol was found in urine within 24 hr after injection. The total recovery of iohexol after 1 week was 96% (range, 87%-101%).