Technetium Tc 99m Medronate

TECHNETIUM TC 99M MEDRONATE — medronic acid injection, powder, for solution
Jubilant DraxImage Inc., dba Jubilant Radiopharma

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DRAXIMAGE® MDP-25

Kit for the Preparation of Technetium Tc 99m Medronate Injection

For Intravenous Use

DIAGNOSTIC – FOR SKELETAL IMAGING

DESCRIPTION

The kit consists of reaction vials which contain the sterile, non-pyrogenic,non-radioactive ingredients necessary to produce Technetium Tc 99m Medronate Injection for diagnostic use by intravenous injection. MDP-25 reaction vials are intended to be used as multidose vials.
Each 10 mL MDP-25 reaction vial contains 25.0 mg medronic acid and not less than 2.0 mg of stannous chloride dihydrate (maximum total tin expressed as stannous chloride dihydrate 3.0 mg) and 5.0 mg of p-aminobenzoic acid in lyophilized form under an atmosphere of nitrogen.
The pH is adjusted to 6.8 to 6.9 with HCI or NaOH prior to lyophilization. The addition of sterile, non-pyrogenic, and oxidant-free sodium pertechnetate Tc-99m sterile solution produces a rapid labeling which is essentially quantitative and which remains stable in vitro throughout the 12-hours life of the preparation. No bacteriostatic preservative is present.
The structural formula of medronic acid is:

Structure
(click image for full-size original)

PHYSICAL CHARACTERISTICS

Technetium Tc-99m decays by isomeric transition with a physical half-life of 6.02 hours.1 The principal photon that is useful for detection and imaging studies is listed in Table 1.
Table 1 Principal Radiation Emission Data

Radiation Mean % / Disintegration

Energy

(keV)

Gamma-2

89.07

140.5

EXTERNAL RADIATION
The specific gamma ray constant for Tc-99m is 0.78 R/mCi-hr at 1 cm. The first half value layer is 0.017 cm of lead. To facilitate control of the radiation exposure from millicurie amounts of this radionuclide, the use of a 0.25 cm thickness of lead will attenuate the radiation emitted by a factor of about 1000. A range of values for the relative attenuation of the radiation emitted by this radionuclide that results from interposition of various thicknesses of lead is shown in Table 2.
Table 2 Radiation Attenuation by Lead Shielding

Shield Thickness(Pb) cm

Coefficient of Attenuation

0.017

0.08

0.16

0.25

0.33

0.5

10-1

10-2

10-3

10-4

To correct for physical decay of this radionuclide, the fractions that remain at selected intervals after the time of calibration are shown in Table 3.
1 Kocher, David C.: “Radioactive Decay Data Tables”, DOE/TIC-11026, 108 (1981)
Table 3 Physical Decay Chart: Tc-99m, half-life 6.02 hours

*Calibration time

Hours

Fraction

Remaining

Hours

Fraction

Remaining

0*

1

2

3

4

5

6

1.000

0.891

0.794

0.708

0.631

0.562

0.501

7

8

9

10

11

12

0.447

0.398

0.355

0.316

0.282

0.251

CLINICAL PHARMACOLOGY

When injected intravenously, Technetium Tc 99m Medronate is rapidly cleared from the blood; about 50% of the dose is accumulated and retained by the skeleton, while the remaining 50% is excreted in the urine within 24 hours. About 10% of the injected dose remains in the blood at 1 hour post-injection, 5% at 2 hours, and less than 1% remains at 24 hours. The resultant blood clearance curve is tri-exponential with the two fastest components accounting for all but a few percent of the injected dose.
Following intravenous administration of Technetium Tc 99m Medronate, skeletal uptake occurs as a function of blood flow to bone and bone efficiency in extracting the complex. Bone mineral crystals are generally considered to be hydroxyapatite, and the complex appears to have an affinity for the hydroxyapatite crystals in the bone.
The rapid blood clearance provides bone to soft-tissue ratios which favor early imaging. The skeletal uptake is bilaterally symmetrical and is greater in the axial skeleton than in the long bones. Areas of abnormal osteogenesis show altered uptake making it possible to visualize a variety of osseous lesions.

INDICATIONS & USAGE

MDP-25 (Kit for the Preparation of Technetium Tc 99m Medronate) may be used as a bone imaging agent to delineate areas of altered osteogenesis.

CONTRAINDICATIONS

None known at present.

WARNINGS

This class of compounds is known to complex cations such as calcium. Particular caution should be used with patients who have, or who may be predisposed to, hypocalcemia (i.e., alkalosis).
The contents of the kit before preparation are not radioactive. However, after the sodium pertechnetate Tc-99m is added, adequate shielding of the final preparation must be maintained.
Preliminary reports indicate impairment of brain images using Sodium Pertechnetate Tc 99m Injection which have been preceded by bone imaging using an agent containing stannous ions. The impairment may result in false-positive or false-negative brain images. It is recommended, where feasible, that brain imaging using Sodium Pertechnetate Tc 99m Injection precede bone imaging procedures. Alternatively, a brain imaging agent such as technetium Tc-99m pentetate may be employed.

PRECAUTIONS

Contents of the reaction vial are intended only for use in the preparation of Technetium Tc 99m Medronate and are NOT to be administered directly to the patient.
To minimize the radiation dose to the bladder, the patient should be encouraged to increase fluid intake and to void as often as possible after the injection of Technetium Tc 99m Medronate, and for 4 to 6 hours after the imaging procedure.
The preparation contains no bacteriostatic preservative.
Both the powdered and reconstituted forms of MDP-25 should be stored at 25°C (77°F); excursions permitted between 15° and 30°C (59° to 86°F). The reconstituted product should be stored in a suitable lead shield. The solution should not be used if it is cloudy.
Optimal imaging results are obtained 1 to 4 hours after administration. The image quality may be adversely affected by obesity, old age and impaired renal function.
General

The components of the kit are sterile and non-pyrogenic. It is essential to follow directions carefully and to adhere to strict aseptic procedures during preparation.
Technetium Tc 99m Medronate as well as other radioactive drugs must be handled with care. Once sodium pertechnetate Tc-99m is added to the vial, appropriate safety measures should be used to minimize external radiation to clinical occupational personnel. Care should also be taken to minimize radiation exposure to patients in a manner consistent with proper patient management.
The technetium Tc-99m labeling reactions involved depend on maintaining the stannous ion in the reduced state. Hence, sodium pertechnetate Tc-99m containing oxidants should not be employed.
Radiopharmaceuticals should be used only by physicians who are qualified by training and experience in the safe use and handling of radionuclides and whose experience and training have been approved by the appropriate government agency authorized to license the use of radionuclides.
Carcinogenesis, Mutagenesis, Impairment of Fertility
No long term animal studies have been performed to evaluate carcinogenic or mutagenic potential or whether Technetium Tc 99m Medronate affects fertility in males or females.
Pregnancy Category C
Animal reproduction and teratogenicity studies have not been conducted with Technetium Tc 99m Medronate. It is also not known whether Technetium Tc-99m Medronate can cause fetal harm when administered to a pregnant woman or can affect reproductive capacity. There have been no studies in pregnant women. Technetium Tc-99m should be given to a pregnant woman only if clearly needed.
Ideally, examinations using radiopharmaceuticals, especially those elective in nature, of a woman of childbearing capability should be performed during the first few (approximately 10) days following the onset of menses.
Nursing Mothers
Technetium Tc-99m is excreted in human milk during lactation. Therefore, formula feedings should be substituted for breast feedings.

Pediatric Use
Safety and effectiveness in pediatric patients have not been established.

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