NEUROLITE

NEUROLITE- bicisate dihydrochloride
Lantheus Medical Imaging, Inc.

DESCRIPTION

This kit formulation consists of two nonradioactive vials: Vial A contains bicisate dihydrochloride (N, N’-1,2-ethylenediylbis-L-cysteine diethyl ester dihydrochloride) and a reducing agent as a lyophilized solid and vial B contains a buffer solution. Both vials are sterile and non-pyrogenic.

Vial A –
Bicisate dihydrochloride (ECD•2HCl) 0.9 mg
Edetate disodium, dihydrate 0.36 mg
Mannitol 24 mg
Stannous chloride, dihydrate, theoretical
(SnCl2 •2H2 O) 72 µg
Stannous chloride, dihydrate,
minimum (SnCl2 •2H2 O) 12 µg
Total Tin, (stannous and stannic), dihydrate
(as SnCl2 •2H2 O) 83 µg

The contents of vial A are lyophilized and stored under nitrogen. The pH of the solution before lyophilization is 2.7 ± 0.25. This vial is stored at 15-25°C. Protect from light.

Vial B –
Sodium phosphate dibasic heptahydrate 4.1 mg
Sodium phosphate monobasic monohydrate 0.46 mg
Water for Injection qs 1 mL

The contents of vial B are stored under air. The pH of the solution is 7.6 ± 0.4. This vial is stored at 15-25°C.

This drug is administered by intravenous injection for diagnostic use after reconstitution with sterile, non-pyrogenic, oxidant-free Sodium Pertechnetate Tc99m Injection. The precise structure of the Technetium complex is [N, N'-ethylenedi-L-cysteinato(3-)]oxo[99m Tc] technetium (V), diethyl ester.

PHYSICAL CHARACTERISTICS

Technetium Tc99m decays by isomeric transition with a physical half-life of 6.02 hrs1. Photons useful for the detection and imaging studies are listed in Table 1.

Table 1. Principle Radiation Emission Data
Radiation Mean % / Disintegration Mean Energy (KeV)

1 Kocher, David C., “Radioactive Decay Data Tables”, DOE/TIC 11026, 108 (1981).

Gamma-2 89.07 140.5

External Radiation

The specific gamma ray constant for Tc99m is 5.4 microcoulombs/kg-MBq-hr (0.78R/mCi-hr) at 1cm. The first half value layer is 0.017cm of lead (Pb). Relative attenuation of the radiation emitted by this radionuclide results from the interposition of various thicknesses of Pb. The corresponding attenuation is shown in Table 2. To facilitate control of the radiation exposure from MBq (mCi) amounts of this radionuclide, a 0.25 cm thickness of Pb will attenuate the radiation by a factor of 1,000.

Table 2. Radiation Attenuation by Lead Shielding
Shield Thickness (Pb) cm Coefficient of Attenuation
0.017 0.5
0.08 10-1
0.16 10-2
0.25 10-3
0.33 10-4

To correct for the physical decay of this radionuclide, the fractions that remain at selected time intervals after the time of calibration are shown in Table 3.

Table 3. Physical Decay Chart; Technetium Tc99m Half-Life 6.02 Hours
Hours Fraction Remaining Hours Fraction Remaining

*Calibration Time

0* 1.000 7 .447
1 .891 8 .398
2 .794 9 .355
3 .708 10 .316
4 .631 11 .282
5 .562 12 .251
6 .501

CLINICAL PHARMACOLOGY

General

Neurolite®, Kit for the Preparation of Technetium Tc99m Bicisate for Injection forms a stable, lipophilic complex which can cross the blood brain barrier. Technetium Tc99m Bicisate crosses intact cell membranes and the intact blood brain barrier by passive diffusion. Five percent of the injected dose remains in the blood at one hour. The amount of Technetium Tc99m Bicisate in the brain is stable until about 6 hours. After background clearance, images of the brain can be obtained from 10 minutes to 6 hours after injection. Optimal images occur 30-60 minutes after injection. Technetium Tc99m Bicisate is cleared primarily by the kidneys.

Pharmacokinetics

In a study in 16 normals (13 men and 3 women, mean age of 31 ± 10 years; mean weight of 72 ± 11 kg), the pharmacokinetic profile in blood best fits a three compartment model with half-lives of 43 seconds, 49.5 minutes and 533 minutes. The highest concentration of radioactivity measured in blood was found at 0.5 minutes after intravenous injection and was 13.9% of the injected dose. Technetium Tc99m Bicisate and its major metabolites are not protein-bound.

Metabolism

Technetium Tc99m Bicisate is metabolized by endogenous enzymes to the mono- and di-acids of Technetium Tc99m Bicisate that can be detected in blood and urine. No studies have been performed to compare the concentration of Technetium Tc99m Bicisate or its metabolites in normal, ischemic and infarcted cells.

Technetium Tc99m Bicisate is excreted primarily through the kidneys. Within two hours, 50% of the injected dose is excreted and by 24 hours, 74% is found in urine. It is not known whether the parent drug molecule or its metabolites are dialyzable. Fecal excretion accounts for 12.5% of the injected dose after 48 hours.

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