Dexrazoxane (Page 2 of 3)
7 DRUG INTERACTIONS
No drug interactions have been identified [see Clinical Pharmacology (12.3) ].
8 USE IN SPECIFIC POPULATIONS
8.1 Pregnancy
Teratogenic Effects. Pregnancy Category D Risk Summary
Dexrazoxane for injection can cause fetal harm when administered to pregnant women. Dexrazoxane administration resulted in maternal toxicity, embryotoxicity and teratogenicity in rats and rabbits at doses significantly lower than the clinically recommended dose. If this drug is used during pregnancy, or if the patient becomes pregnant while taking this drug, the patient should be apprised of the potential hazard to a fetus [see Warnings and Precautions (5.5)].
Animal Data
Dexrazoxane resulted in maternal toxicity in rats at doses of ≥2 mg/kg (1/40 the human dose on a mg/m2 basis) and embryotoxicity and teratogenicity at 8 mg/kg (approximately 1/10 the human dose on a mg/m2 basis) when given daily to pregnant rats during the period of organogenesis. Teratogenic effects in the rat included imperforate anus, microphthalmia, and anophthalmia. In offspring allowed to develop to maturity, fertility was impaired in the male and female rats treated in utero during organogenesis at 8 mg/kg. In rabbits, doses of ≥5 mg/kg (approximately 1/10 the human dose on a mg/m2 basis) daily during the period of organogenesis caused maternal toxicity and doses of 20 mg/kg (1/2 the human dose on a mg/m2 basis) were embryotoxic and teratogenic. Teratogenic effects in the rabbit included several skeletal malformations such as short tail, rib and thoracic malformations, and soft tissue variations including subcutaneous, eye and cardiac hemorrhagic areas, as well as agenesis of the gallbladder and of the intermediate lobe of the lung.
8.3 Nursing Mothers
It is not known whether dexrazoxane or its metabolites are excreted in human milk. Because many drugs are excreted in human milk and because of the potential for serious adverse reactions in nursing infants from dexrazoxane, a decision should be made whether to discontinue nursing or discontinue the drug, taking into account the importance of the drug to the mother.
8.4 Pediatric Use
The safety and effectiveness of dexrazoxane in pediatric patients have not been established [see Warnings and Precautions (5.4)].
8.5 Geriatric Use
Clinical studies of dexrazoxane for injection did not include sufficient numbers of subjects aged 65 and over to determine whether they respond differently than younger subjects. 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 starting at 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.
8.6 Females of Reproductive Potential
Contraception
Dexrazoxane for injection can cause fetal harm when administered during pregnancy. Advise female patients of reproductive potential to use highly effective contraception during treatment [see Use in Specific Populations (8.1 )].
8.7 Renal Impairment
Greater exposure to dexrazoxane may occur in patients with compromised renal function. Reduce the dexrazoxane for injection dose by 50% in patients with creatinine clearance values <40 mL/min [see Dosage and Administration (2.2) and Clinical Pharmacology (12.3 )].
10 OVERDOSAGE
There are no data on overdosage in the cardioprotective trials; the maximum dose administered during the cardioprotective trials was 1000 mg/m2 every three weeks.
Disposition studies with dexrazoxane for injection have not been conducted in cancer patients undergoing dialysis, but retention of a significant dose fraction (>0.4) of the unchanged drug in the plasma pool, minimal tissue partitioning or binding, and availability of greater than 90% of the systemic drug levels in the unbound form suggest that it could be removed using conventional peritoneal or hemodialysis.
There is no known antidote for dexrazoxane. Instances of suspected overdose should be managed with good supportive care until resolution of myelosuppression and related conditions is complete. Management of overdose should include treatment of infections, fluid regulation, and maintenance of nutritional requirements.
11 DESCRIPTION
Dexrazoxane for Injection, a cardioprotective agent for use in conjunction with doxorubicin, is a sterile, pyrogen-free lyophilizate intended for intravenous administration.
Chemically, dexrazoxane is (+)-(S)-4,4’-Propylenedi-2,6-piperazinedione. The structural formula is as follows:
Structural Formula
C11 H16 N4 O4 M.W. 268.27
Dexrazoxane, an intracellular chelating agent, is a derivative of EDTA. Dexrazoxane is a whitish crystalline powder that melts at 191° to 197°C. It is sparingly soluble in water and 0.1 N HCl, slightly soluble in ethanol and methanol, and practically insoluble in nonpolar organic solvents. The pKa is 2.1. Dexrazoxane has an octanol/water partition coefficient of 0.025 and degrades rapidly above a pH of 7.0.
Each 250 mg vial contains dexrazoxane hydrochloride equivalent to 250 mg dexrazoxane. Hydrochloric Acid, NF is added for pH adjustment. When reconstituted as directed with 25 mL of Sterile Water for Injection, USP, each mL contains: 10 mg dexrazoxane. The pH of the resultant solution is 1.0 to 3.0.
Each 500 mg vial contains dexrazoxane hydrochloride equivalent to 500 mg dexrazoxane. Hydrochloric Acid, NF is added for pH adjustment. When reconstituted as directed with 50 mL of Sterile Water for Injection, USP, each mL contains: 10 mg dexrazoxane. The pH of the resultant solution is 1.0 to 3.0.
The reconstituted dexrazoxane for injection solutions prepared from Sterile Water for Injection, USP, are intended for further dilution with Lactated Ringer’s Injection, USP, for rapid intravenous drip infusion. DO NOT ADMINISTER VIA AN INTRAVENOUS PUSH [see Dosage and Administration (2.1 , 2.3)].
12 CLINICAL PHARMACOLOGY
12.1 Mechanism of Action
The mechanism by which dexrazoxane for injection exerts its cytoprotective activity is not fully understood. Dexrazoxane is a cyclic derivative of EDTA that penetrates cell membranes. Results of laboratory studies suggest that dexrazoxane is converted intracellularly to a ring-opened chelating agent that interferes with iron-mediated free radical generation thought to be responsible, in part, for anthracycline-induced cardiomyopathy.
12.3 Pharmacokinetics
The pharmacokinetics of dexrazoxane have been studied in advanced cancer patients with normal renal and hepatic function. The pharmacokinetics of dexrazoxane can be adequately described by a two-compartment open model with first-order elimination. Dexrazoxane has been administered as a 15 minute infusion over a dose range of 60 to 900 mg/m2 with 60 mg/m2 of doxorubicin, and at a fixed dose of 500 mg/m2 with 50 mg/m2 doxorubicin. The disposition kinetics of dexrazoxane are dose-independent, as shown by linear relationship between the area under plasma concentration-time curves and administered doses ranging from 60 to 900 mg/m2. The mean peak plasma concentration of dexrazoxane was 36.5 mcg/mL at 15- minute after intravenous administration of 500 mg/m2 dose of dexrazoxane for injection over 15 to 30 minutes prior to the 50 mg/m2 doxorubicin dose.
The important pharmacokinetic parameters of dexrazoxane are summarized in Table 2:
Table 2: SUMMARY OF MEAN (%CVa) DEXRAZOXANE PHARMACOKINETIC PARAMETERS AT A DOSAGE RATIO OF 10:1 OF DEXRAZOXANE FOR INJECTION:DOXORUBICIN
| Dose | Dose | Number of | Elimination | Plasma | Renal | bVolume of |
| Doxorubicin (mg/m2) | Dexrazoxane (mg/m2) | Subjects | Half-Life (h) | Clearance (L/h/m2) | Clearance (L/h/m2) | Distribution (L/m2) |
| 50 | 500 | 10 | 2.5 (16) | 7.88 (18) | 3.35 (36) | 22.4 (22) |
| 60 | 600 | 5 | 2.1 (29) | 6.25 (31) | — | 22.0 (55) |
a Coefficient of variation
b Steady-state volume of distribution
Distribution
Following a rapid distributive phase (0.2 to 0.3 hours), dexrazoxane reaches post-distributive equilibrium within two to four hours. The estimated mean steady-state volume of distribution of dexrazoxane is 22.4 L/m2 after 500 mg/m2 of dexrazoxane for injection dose followed by 50 mg/m2 of doxorubicin, suggesting distribution throughout total body water (25 L/m2).
In vitro studies have shown that dexrazoxane is not bound to plasma proteins.
Metabolism
Qualitative metabolism studies with dexrazoxane have confirmed the presence of unchanged drug, a diacid-diamide cleavage product, and two monoacid-monoamide ring products in the urine of animals and man. The metabolite levels were not measured in the pharmacokinetic studies.
Excretion
Urinary excretion plays an important role in the elimination of dexrazoxane. Forty-two percent of a 500 mg/m2 dose of dexrazoxane for injection was excreted in the urine. Renal clearance averages 3.35 L/h/m2 after the 500 mg/m2 dexrazoxane for injection dose followed by 50 mg/m2 of doxorubicin.
Specific Populations
Pediatric
Pharmacokinetics following dexrazoxane for injection administration have not been evaluated in pediatric patients.
Effect of Renal Impairment
The pharmacokinetics of dexrazoxane were assessed following a single 15-minute IV infusion of 150 mg/m2 of dexrazoxane for injection. Dexrazoxane clearance was reduced in subjects with renal dysfunction. Compared with controls, the mean AUC0-inf value was two-fold greater in subjects with moderate (CLCR 30-50 mL/min) to severe (CLCR <30 mL/min) renal dysfunction.
Modeling demonstrated that equivalent exposure (AUC-inf ) could be achieved if dosing were reduced by 50% in subjects with creatinine clearance values <40 mL/min compared with control subjects (CLCR >80 mL/min) [see Use in Specific Populations (8.7) and Dosage and Administration (2.2 )].
Effect of Hepatic Impairment
Pharmacokinetics following dexrazoxane for injection administration have not been evaluated in patients with hepatic impairment. The dexrazoxane for injection dose is dependent upon the dose of doxorubicin [see Dosage and Administration (2.2)].
Drug Interactions
There was no significant change in the pharmacokinetics of doxorubicin (50 mg/m2) and its predominant metabolite, doxorubicinol, in the presence of dexrazoxane (500 mg/m2) in a crossover study in cancer patients.
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