2.1 Radiation Safety – Drug Handling

After radiolabeling, handle Technetium Tc 99m Succimer Injection with appropriate safety measures to minimize radiation exposure [see Warnings and Precautions (5.2)]. Use waterproof gloves, effective radiation shielding, and other appropriate safety measures when preparing and handling Technetium Tc 99m Succimer Injection.

Radiopharmaceuticals should be used by or under the control of physicians who are qualified by specific training and experience in the safe use and handling of radionuclides, and whose experience and training have been approved by the appropriate governmental agency authorized to license the use of radionuclides.

2.2 Patient Preparation

Instruct patients to drink a sufficient amount of water to ensure adequate hydration prior to administration of Technetium Tc 99m Succimer Injection and to continue to drink and void frequently following administration to reduce radiation exposure [see Warnings and Precautions (5.2)].

2.3 Recommended Dosage

2.4 Drug Preparation

Prepare Technetium Tc 99m Succimer Injection according to the following procedure using asceptic technique:

1. Wear waterproof gloves.
2. Place the kit vial in lead shielding and disinfect the stopper (allow disinfectant to dry).
3. Use a sterile syringe to transfer 5 mL sodium pertechnetate Tc 99m injection obtained from a technetium Tc 99m generator with a maximum activity of 1,480 MBq (40 mCi) to the vial. The volume of sodium pertechnetate Tc 99m injection may be adjusted to 5 mL prior to adding to the kit vial using 0.9% sodium chloride injection, USP.
4. Use the same syringe to withdraw the appropriate gas volume from the vial for pressure compensation.
5. Lightly shake the vial to completely dissolve the powder. Ensure the stopper is well moistened.
6. Incubate the vial for 10 minutes at controlled room temperature 20°C to 25°C (68°F to 77°F).
7. Measure the product activity in a dose calibrator; complete the radiolabeled product vial label and affix to the vial shield.
8. Check radiochemical purity according to the method in 2.5 Radiochemical Purity Determination [see Dosage and Administration (2.5)].
9. Use Technetium Tc 99m Succimer Injection within 4 hours and store at controlled room temperature 20°C to 25°C (68°F to 77°F); excursions permitted to 15°C to 30°C (59°F to 86°F).

2.5 Radiochemical Purity Determination

Determine the radiochemical purity of Technetium Tc 99m Succimer Injection as follows:

1. Activate a 65 × 95-mm silicic acid thin-layer chromatographic (TLC) plate by heating at 100°C to 110°C (212°F to 230°F) for 30 minutes.
2. Cool the TLC plate over silica gel and immediately apply 1 microL of Technetium Tc 99m Succimer Injection about 17 mm from one end of the TLC plate and allow to dry. If necessary, the Technetium Tc 99m Succimer Injection may be diluted with 0.9% sodium chloride injection USP, to a radioactive concentration of 18.5 MBq to 370 MBq (0.5 mCi to 10 mCi) per mL.
3. Develop the TLC plate over a period of about 30 minutes to 45 minutes by ascending chromatography, using a solution of n-butanol saturated with 0.3 N hydrochloric acid (see Note 1). Air-dry the developed TLC Plate.
4. Determine the radioactive distribution on the TLC plate by scanning the chromatogram with a radiochromatographic scanner having a suitably collimated radiation detector.
5. The radioactivity associated with technetium Tc 99m succimer is at Rf between 0.45 and 0.7, hydrolyzed Tc 99m is located at the origin (Rf 0 to 0.15) and the unbound Tc 99m is located at the solvent front (Rf 1)
   
   
6. Calculate radiochemical purity using the following formula:
   
   
7. Technetium Tc 99m Succimer Injection preparation with not less than 85% radiochemical purity is suitable for administration. Discard preparation with less than 85% radiochemical purity.

Note 1: To prepare the n-butanol saturated with 0.3 N hydrochloric acid solution, place 50 mL of 0.3 N HCl and 50 mL of n-butanol in an Erlenmeyer flask. Place the mixture in an ultrasonic bath for 2 hours, during which time the solution heats up to about 50°C. Cool the solution to room temperature. After about 30 minutes to 45 minutes the phase separation of the mixture will complete. Collect the upper phase of the mixture and discard the lower phase. The solution is stable for up to 7 days when stored at controlled room temperature 20°C to 25°C (68°F to 77°F).

2.6 Administration

Prior to use, visually inspect the prepared Technetium Tc 99m Succimer Injection behind a lead glass shield. Only use solutions that are clear without visible particles.

In making dosage calculations, correction is to be made for radioactive decay. The radioactive half-life of Tc 99m is 6.0 hours.

Using a sterile shielded syringe, aseptically withdraw the prepared Technetium Tc 99m Succimer Injection, and measure the radioactivity in the syringe using a dose calibrator, prior to administration. Ensure that the injected radioactivity is within ±10% of the recommended dose.

Discard unused portion. Handle and dispose radioactive material in accordance with applicable regulations.

2.7 Image Acquisition

The patient should be placed in the prone or supine position, as required by scanning equipment characteristics. Begin image acquisition 1 hour to 4 hours after the intravenous administration of Technetium Tc 99m Succimer Injection.

Delay image acquisition up to 6 hours to 24 hours in patients with severely reduced glomerular filtration rate (eGFR). A specific eGFR threshold at which to delay imaging has not been established [see Warnings and Precautions (5.3)].

2.8 Radiation Dosimetry

The estimated absorbed radiation doses to an average adult and pediatric patients are shown in Table 2.

5.1 Hypersensitivity Reactions

Hypersensitivity reactions, including urticaria, rash, pruritus, and erythema have been reported with the use of technetium Tc 99m succimer injection in adults and pediatric patients. The time of onset of the reactions varied within 2 hours to several hours after the injection. Have appropriate instruments and medications necessary for immediate treatment of hypersensitivity reactions and monitor patients for reactions during and after administration [see Adverse Reactions (6)].

5.2 Radiation Risks

Technetium Tc 99m succimer injection contributes to a patient's overall long-term cumulative radiation exposure. Long-term cumulative radiation exposure is associated with an increased risk for cancer. Ensure safe handling to minimize radiation exposure to the patient and health care workers. Advise patients to hydrate before and after administration and to void frequently after administration [see Dosage and Administration (2.1, 2.2)].

5.3 Risk in Patients with Advanced Renal Failure

The use of technetium Tc 99m succimer injection in patients with severely reduced estimated glomerular filtration (eGFR) may have an effect on image interpretation as the kidneys may not absorb the technetium Tc 99m succimer and thus the Tc 99m succimer may distribute to organs or parts of the body other than the kidneys. It has been reported that satisfactory images may be obtained in some of these patients by delaying imaging between 6 hours to 24 hours [see Dosage and Administration (2.7)].

8.1 Pregnancy

8.2 Lactation

8.4 Pediatric Use

NEPHROSCAN, after radiolabeling with technetium Tc 99m, is indicated for use as an aid in the scintigraphic evaluation of renal parenchymal disorders in pediatric patients, including term neonates. Use of NEPHROSCAN in this age group for this indication is supported by evidence from effectiveness established in adult studies and data from published pediatric studies supporting the safety and effectiveness of weight-based dosing of Technetium Tc 99m Succimer Injection in renal parenchymal imaging in pediatric patients including term neonates [see Dosage and Administration (2.3)].

The recommended amount of radioactivity in pediatric patients, 1.85 MBq/kg (0.05 mCi/kg) with a range of 19 MBq to 74 MBq (0.5 mCi to 2 mCi), is based on published studies that used technetium Tc 99m succimer for the evaluation of acute pyelonephritis, renal scarring, and split renal function in pediatric patients [see Dosage and Administration (2.2)].

Hypersensitivity reactions, including urticaria, rash, pruritus, and erythema have been reported with the use of technetium Tc 99m succimer in pediatric patients [see Warnings and Precautions (5.1) and Adverse Reactions (6)].

8.5 Geriatric Use

Clinical studies of technetium Tc 99m succimer did not include sufficient numbers of subjects 65 years of age and over to determine whether they respond differently from younger patients. Other reported clinical experience has not identified differences in responses between the elderly and younger patients. In general, dose selection for an elderly patient should be cautious usually administering the low end of the dosing range, reflecting the greater frequency of decreased hepatic, renal or cardiac function, and of concomitant disease or other drug therapy.

This drug is known to be substantially excreted by the kidney, and the risk of toxic reactions to this drug may be greater in patients with decreased renal function. Because elderly patients are more likely to have decreased renal function, care should be taken in dose selection, and it may be useful to monitor renal function.

11.1 Chemical Characteristics

NEPHROSCAN is a sterile, single-dose kit for the preparation of Technetium Tc 99m Succimer Injection a radioactive diagnostic agent, for intravenous use.

The active ingredient, succimer is meso-2,3-dimercaptosuccinic acid with a molecular weight of 182.22 g/mol. The chemical structure of succimer is shown below. Subsequent to radiolabeling with sodium pertechnetate Tc 99m, the active moiety technetium Tc 99m succimer is obtained in situ.

Each vial contains 1 mg succimer, 0.1 mg ascorbic acid, 0.42 mg stannous (tin) chloride dihydrate, 0.02 mg hydrochloric acid and 0.2 mg sodium hydroxide as a white-yellowish to off-white lyophilized powder.

In addition, after radiolabeling with sodium pertechnetate Tc 99m injection, each vial contains up to 1,480 MBq (40 mCi) of technetium Tc 99m succimer in 0.9% sodium chloride injection as a sterile, clear, and colorless solution. pH of the final solution is between 3 and 3.5. FDA approved pH specifications differ from USP.

11.2 Physical Characteristics

Technetium Tc 99m decays by isomeric transition with a physical half-life of 6.02 hours. The principal photon that is useful for detection and imaging studies is listed in Table 3.

To correct for physical decay of this radionuclide, the fractions that remain at selected intervals after the time of calibration are shown in Table 4.

11.3 External Radiation

The specific gamma ray constant for technetium Tc 99m is 0.78 R/hr-mCi at 1 cm. The first half value layer is 0.017 cm of Pb. To facilitate control of the radiation exposure from millicurie amounts of this radionuclide, the use of a 0.25 cm thickness of Pb will attenuate the radiation emitted by a factor of about 1,000. Table 5 displays the radiation attenuation by lead shielding.

12.1 Mechanism of Action

Technetium Tc 99m succimer binds to the cortical region of kidneys and in conjunction with gamma scintigraphy or single photon emission computed tomography (SPECT) is used to image the renal cortices.

12.2 Pharmacodynamics

Technetium Tc 99m succimer only stays bound to viable cortical tissue for >24 hours following administration. The relationship between technetium Tc 99m succimer plasma concentrations and successful imaging is not known.

12.3 Pharmacokinetics

13.1 Carcinogenesis, Mutagenesis, Impairment of Fertility

No long-term animal studies were performed to evaluate the carcinogenicity potential of technetium Tc 99m succimer.

How Supplied

NEPHROSCAN (kit for the preparation of technetium Tc 99m succimer injection), containing 1 mg succimer, is supplied as a white-yellowish to off-white lyophilized powder packaged in a sterile, single-dose vial as a carton of 5 vials (NDC 71083-0020-5).

Storage and Handling

Before radiolabeling, store NEPHROSCAN in a refrigerator at 2°C to 8°C (36°F to 46°F) in original carton. Do not freeze.

After radiolabeling, store Technetium Tc 99m Succimer Injection upright, shielded, for up to 4 hours, at controlled room temperature 20°C to 25°C (68°F to 77°F); excursions permitted to 15°C to 30°C (59°F to 86°F) [see Dosage and Administration (2.4)].

This preparation is approved for use by persons under license by the Nuclear Regulatory Commission or the relevant regulatory authority of an Agreement State.

Adequate Hydration

Instruct patients to drink a sufficient amount of water to ensure adequate hydration before their imaging and urge them to drink and urinate as often as possible during the first hours following the administration of Technetium Tc 99m Succimer Injection, in order to reduce radiation exposure [see Dosage and Administration (2.2) and Warnings and Precautions (5.2)].

Lactation

Advise a lactating woman to temporarily discontinue breastfeeding and to pump and discard breast milk for at least 24 hours after Technetium Tc 99m Succimer Injection administration in order to minimize radiation exposure to a breastfed infant [see Use in Specific Populations (8.2)].