Prescription Drug Information: Radiogardase

RADIOGARDASE- ferric ferrocyanide capsule
Heyl Chem.-pharm. Fabrik GmbH & Co. KG

1 INDICATIONS AND USAGE

Radiogardase is indicated for treatment of patients with known or suspected internal contamination with radioactive cesium and/or radioactive or non-radioactive thallium, in order to increase their rates of elimination.

2 DOSAGE AND ADMINISTRATION

2.1 Important Administration Instructions

  • Obtain quantitative baseline of the internalized contamination by radioactive cesium (137Cs) and/or thallium by appropriate whole-body counting and/or by bioassay (e.g., biodosimetry), or feces/urine samples, whenever possible prior to Radiogardase treatment.
  • Initiate treatment with Radiogardase as soon as possible after contamination is suspected. Even when delayed, treatment with Radiogardase is effective and should not be withheld.
  • Take Radiogardase capsules with food to stimulate excretion of cesium or thallium.
  • In patients who cannot tolerate swallowing large numbers of capsules, open the capsules and mix with bland food or liquids.

2.2 Decontamination Procedures for Radioactive Cesium or Thallium Contamination

Prior to initiating treatment with Radiogardase, follow radioactive decontamination safety procedures including:

  • Use appropriate radiation protective attire and closely monitor personnel and treatment area for radiation levels using radiation detection, indication, and computation devices (RADIAC) or thermal luminescent devices (TLD).
  • Control spread of radiation contamination through the establishment of a patient decontamination area and a contaminated material disposal site (with proper labeling, handling, and disposal of contaminated material).

2.3 Recommended Dosage

  • Adults and Adolescents: 3 grams (6 capsules) taken orally three times a day (a total daily dose of 9 grams)
  • Pediatric Patients (2 – 12 years): 1 gram (2 capsules) taken orally three times a day (a total daily dose of 3 grams)

2.4 Treatment of Radioactive Cesium Contamination

  • Anticipate that treatment with Radiogardase may last 30 days or longer.
  • Base duration of Radiogardase treatment on weekly measurements of radioactivity in urine and fecal samples to monitor cesium elimination rate.
  • Obtain weekly laboratory evaluations (complete blood count, serum chemistry and electrolytes).

2.5 Treatment of Radioactive and Non-radioactive Thallium Contamination

  • Anticipate that treatment with Radiogardase may last 30 days or longer.
  • For radioactive thallium:
    • Base duration of Radiogardase treatment on weekly measurements of radioactivity inurine and fecal samples to monitor thallium elimination rate.
    • Continue Radiogardase treatment until a 24-hour urine thallium test is normal (less than 5 micrograms per liter) and radiation level is acceptable.
  • For non-radioactive thallium: Continue Radiogardase treatment until a 24-hour urine thallium test is normal (less than 5 micrograms per liter).
  • Obtain weekly laboratory evaluations (complete blood count, serum chemistry and electrolytes).
  • In cases of severe thallium intoxication, additional types of treatment may be necessary, such as:
    • Induced emesis, followed by gastric intubation and lavage
    • Forced diuresis until urinary thallium excretion is less than 1 mg/24 hours
    • Charcoal hemoperfusion may be useful during the first 48 hours after thallium ingestion (biodistribution phase).
    • Hemodialysis has also been reported to be effective in thallium intoxication.

3 DOSAGE FORMS AND STRENGTHS

Capsules: 0.5 grams — dark blue capsule is imprinted with the light blue inscription: Heyl imprint image PB

4 CONTRAINDICATIONS

None

5 WARNINGS AND PRECAUTIONS

5.1 Increased Radiation Absorbed Dose to Gastrointestinal Mucosa

Radiogardase can decrease gastrointestinal motility, thus slowing the transit time of radioactivity in the gastrointestinal tract. The slowed transit time can increase the radiation absorbed dose to the gastrointestinal mucosa.

5.2 Constipation

Radiogardase can cause constipation. Monitor and treat for signs and symptoms of constipation. Patients with disorders associated with decreased gastrointestinal motility are at higher risk.

5.3 Electrolyte Abnormalities

Radiogardase may bind to electrolytes found in the gastrointestinal tract. Hypokalemia, with serum potassium values of 2.5 – 2.9 (normal 3.5 – 5.0), was reported in 3 (7%) of 42 patients during treatement with Radiogardase. Monitor serum electrolytes during Radiogardase treatment, particularly when treating patients with pre-existing cardiac arrhythmias or electrolyte imbalances.

5.4 Blue Discoloration of Feces, Oral Mucosa, and Dentition

Radiogardase is excreted primarily in feces and turns stools blue. When Radiogardase capsules are opened and the contents eaten with food, the oral mucosa and dentition may also be colored blue.

6 ADVERSE REACTIONS

Constipation was reported in 10 (24%) of 42 patients treated with Radiogardase. Severity of constipation was mild in 7 patients and moderate in 3 patients [see Warnings and Precautions (5.2)].

7 DRUG INTERACTIONS

Based on animal data, co-administration of Radiogardase with other decorporation agents does not affect the efficacy of Radiogardase for treatment of internal contamination with radioactive cesium and/or radioactive or non-radioactive thallium.

8 USE IN SPECIFIC POPULATIONS

8.1 Pregnancy

Pregnancy Category C
It is not known whether Radiogardase can cause fetal harm when administered to a pregnant woman or if it can affect reproduction capacity. Animal reproduction studies have not been conducted with prussian blue insoluble. However, since Radiogardase is not absorbed from the gastrointestinal tract, effects on the fetus are not expected.

Radioactive cesium ( 137 Cs) crosses the human placenta. One patient, contaminated with 0.005 mCi 137 Cs during her 4 th month of pregnancy, was not treated with Radiogardase. At birth, the concentration of 137 Cs was the same in the mother and the infant.

Thallium crosses the human placenta. Reported fetal effects include failure to thrive and death. The toxicity from untreated radioactive cesium or thallium exposure is greater than the potential reproductive toxicity of Radiogardase.

8.3 Nursing Mothers

Studies to determine if Radiogardase is excreted in human milk have not been conducted. Since Radiogardase is not absorbed from the gastrointestinal tract, its excretion in milk is unlikely. However, cesium and thallium are transmitted from mother to infant in breast milk. Women internally contaminated with cesium or thallium should not breastfeed.

8.4 Pediatric Use

Radioactive Cesium Contamination
The safety and efficacy of Radiogardase in the treatment of 137 Cs in pediatric patients ages, 2 to 18 years old, was established from data from Radiogardase-treated pediatric patients exposed to 137 Cs in the Goiânia, Brazil, contamination incident and from Radiogardase-treated adults exposed to 137 Cs [see Clinical Studies (14.1)].

Overall, 27 pediatric patients received Radiogardase in the range of 3 to 10 grams per day in divided doses (the maximum recommended adolescent dosage is 9 grams per day). Radiogardase treatment reduced the whole body effective half-life of 137 Cs by 46% in adolescents and by 43% in children aged 4 to 12 years of age. In 12 patients for whom the rate of radiation elimination data are available, the rate was similar to that in adults treated with 3 grams three times daily and in pediatric patients treated with 1 gram three times daily. By body weight, the dose ranged from

0.32 gram/kg in the 12-year old patient (10 gram Radiogardase daily dose, 31 kg weight) to

0.21 gram/kg in the 4 year old patient (3 gram Radiogardase daily dose, 14 kg weight) [see Clinical Studies (14.1)] .

Pediatric patients aged 2 up to 4 years are expected to have biliary and gastrointestinal function that is comparable to that of a 4-year old.

The safety and efficacy of Radiogardase has not been established in the treatment of 137 Cs contamination in pediatric patients 0 to 2 years old. There are differences in the developmental maturity of the biliary system and gastrointestinal tract of neonates and infants (0 – 2 years). The dosage-related adverse reactions of Radiogardase on an immature gastrointestinal tract are not known.

Radioactive and Non-Radioactive Thallium Contamination
The safety and efficacy of Radiogardase for the treatment of radioactive and non-radioactive thallium contamination in pediatric patients has not been established.

8.5 Geriatric Use

The safety and efficacy of Radiogardase in patients aged 65 and over have not been evaluated, to determine whether they respond differently from younger subjects.. In general, elderly patients should be monitored closely, reflecting the greater frequency of decreased cardiac function and of concomitant disease or other drug therapy.

8.6 Hepatic Impairment

Radiogardase is not systemically bioavailable and does not rely on hepatic metabolism for activation or inactivation. However, Radiogardase may be less effective in patients with hepatic impairment, due to decreased excretion of cesium and thallium in the bile.

10 OVERDOSAGE

Based on reported adverse reactions and mechanism of action, possible overdosage symptoms may include constipation, obstruction, or severe decrease in electrolytes. Gastric distress was reported in 3 patients treated with 20 gram/day of Radiogardase (approximately 2.2 times the maximum recommended dosage). In these patients, the dose was reduced to 10 gram/day for continued treatment.

11 DESCRIPTION

Radiogardase (prussian blue insoluble) is a decorporation agent for oral use. Radiogardase capsules contain insoluble ferric hexacyanoferrate(II), with an empirical formula of Fe 4 [Fe(CN) 6 ] 3 and a molecular weight of 859.3 Daltons. It is supplied as 0.5 gram of blue powder in gelatin capsules with 0 – 38 mg of microcrystalline cellulose. The dark blue capsule is imprinted with the light blue inscription: Heyl imprint image PB. The powder may vary from uniformly fine, dark granules to coarse light and dark-colored granules. The structural formula for prussian blue insoluble is shown below.

Structural formula for Prussian blue insoluble
(click image for full-size original)

The crystal structure of prussian blue insoluble is a cubic lattice with the Fe II and Fe III atoms occupying the corners of the cube and the cyanide groups positioned on the sides.

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