DESCRIPTION
In-111 DTPA is supplied as a sterile, pyrogen-free, isotonic, aqueous solution that is buffered to pH 7 to 8. At calibration time, each milliliter contains 2.5 mCi of Pentetate Indium Disodium In-111 (no carrier-added) and sodium bicarbonate for pH adjustment.
CHARACTERISTICS
Indium 111 decays by electron capture with a physical half-life of 67.9 hour. The energies of the photons that are useful for detection and imaging studies are:
Radiation Mean % Disintegration Mean Energy (keV)
Gamma-2 90.2 171.3
Gamma-3 94.0 245.4
CLINICAL PHARMACOLOGY
After intrathecal administration, the In-111 DTPA is absorbed from the subarachnoid space and the remainder flows superiorly to the basal cisterns within 2 to 4 hours and subsequently will be apparent in the Sylvian cisterns, the interhemispheric cisterns, and over the cerebral convexities. In normal individuals, the it will have ascended to the parasagittal region within 24 hours with simultaneous partial or complete clearance of activity from the basal cisterns and Sylvian regions. In contrast to air, In-111 DTPA does not normally enter the cerebral ventricles
DOSAGE AND ADMINISTRATION
Extreme care must be exercised to assure aseptic conditions in intrathecal injections. The maximum recommended intrathecal dose in the average patient (70kg) is 18.5 megabecquerels (500 microcuries). The patient dose should be measured by a suitable radioactivity calibration system immediately prior to administration. Parenteral drug preparations should be inspected visually for particulate matter and discoloration prior to administration whenever solution and container permit.
