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CERETEC™
Kit for the Preparation of Technetium Tc99m Exametazime Injection

Diagnostic Radiopharmaceutical
For intravenous use only

DRUG DESCRIPTION

The Ceretec (technetium tc99m exametazime injection) kit is supplied as five packs of three vials for use in the preparation of a technetium Tc99m exametazime intravenous injection as a diagnostic radiopharmaceutical for use as an adjunct in the detection of altered regional cerebral perfusion and for the radiolabeling of autologous leukocytes. Each vial of Ceretec (technetium tc99m exametazime injection) contains a pre-dispensed sterile, non-pyrogenic, lyophilized mixture of 0.5 mg exametazime [(RR,SS)-4.8-diaza-3,6,6,9-tetramethylundecane-2,10-dione bisoxime], 7.6 µg stannous chloride dihydrate (minimum stannous tin 0.6 µg; maximum total stannous and stannic tin 4.0 µg per vial) and 4.5 mg sodium chloride, sealed under nitrogen atmosphere with a rubber closure. The product contains no antimicrobial preservative.

In addition, each package contains five 1 ml vials of Methylene Blue Injection USP 1% containing 10 mg methylene blue USP in Water for Injection q.s. pH adjusted with sodium hydroxide and/or hydrochloric acid, when necessary.

Methylene Blue Injection USP is a sterile, non-pyrogenic solution of phenothiazin-5-ium,3,7-bis (dimethylamino)-chloride, trihydrate. Each package also contains five 4.5 ml vials of 0.003 M Monobasic Sodium Phosphate USP and Dibasic Sodium Phosphate USP in 0.9% Sodium Chloride Injection USP. The solution is sterile and non-pyrogenic. Each ml contains 0.276 mg monobasic sodium phosphate monohydrate, 0.142 mg dibasic sodium phosphate anhydrous and 9 mg sodium chloride in Water for Injection q.s. The total calculated osmolarity of the 0.003 M Monobasic Sodium Phosphate USP and Dibasic Sodium Phosphate USP in 0.9% Sodium Chloride Injection USP is 317 mOsmol/L. Each ml provides 0.285 mg (3mM) of phosphate, 0.157 mEq of sodium and 0.154 mEq of chloride. When used according to the preparation instructions (see DOSAGE AND ADMINISTRATION), Methylene Blue Sodium Phosphates/Sodium Chloride mixture acts as a stabilizer.

Prior to publication of the USAN, exametazime was formerly known as hexamethylpropylene amine oxime (HM-PAO). The name HM-PAO appears in many publications.

The structural formula of exametazime is:

Exametazime Structural Formula Illustration

When sterile pyrogen-free sodium pertechnetate Tc99m in isotonic saline is added to the vial of Ceretec (technetium tc99m exametazime injection) , aTc99m complex of exametazime is formed.

Administration is by intravenous injection for diagnostic use.

Physical Characteristics

Technetium Tc99m decays by isomeric transition with a physical half-life of 6.03 hours.(1) Photons that are useful for imaging studies are listed in Table 1.

Table 1. Principal Radiation Emission Data-technetium Tc99m

Radiation Mean %/ Disintegration Mean Energy (keV)
Gamma 2 87.87 140.5
(1)Dillman, L.T. and Von der Lage, F.C. Radionuclide decay schemes and nuclear parameters for use in radiation-dose estimation. MIRD Phamphlet No. 10, p. 62,1975.

External radiation

The specific gamma ray constant for technetium Tc99m is 206 microCoulomb kg-1/37 MBq-h, (0.8 R/millicurie-h) at 1 cm. The first half-value thickness of lead (Pb) for technetium Tc99m is 0.2 mm. A range of values for the relative attenuation of the radiation emitted by this radionuclide that results from interposition of various thicknesses of Pb is shown in Table 2. For example, the use of a 2.7 mm thickness of Pb will decrease the external radiation exposure by a factor of 1,000.

Table 2. Radiation Attenuation by Lead Shielding

Shield Thickness (Pb) mm Coefficient of Attenuation
0.2 0.5
0.95 10-1
1.8 10-2
2.7 10-3
3.6 10-4
4.5 10-5

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

Table 3. Physical Decay Chart - Tc99m half-life 6.03 hours

Hours Fraction Remaining Hours Fraction Remaining
0* 1.000 7 0.447
1 0.891 8 0.399
2 0.795 9 0.355
3 0.708 10 0.317
4 0.631 11 0.282
5 0.563 12 0.252
6 0.502 24 0.063
*Calibration time (time of preparation)

Last reviewed on RxList: 1/21/2009
This monograph has been modified to include the generic and brand name in many instances.