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BENZNIDAZOLE
(benznidazole) Tablets, for Oral Use
Benznidazole Tablets contain benznidazole, a nitroimidazole antimicrobial. The chemical name of benznidazole is N-benzyl-2-(2-nitro-1H-imidazol-1-yl) acetamide. The empirical formula is C12H12N4O3 and the molecular weight is 260.246 g/mol. The structural formula is:
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Benznidazole is a yellowish, practically crystalline powder that is practically insoluble in water, sparingly soluble in acetone and ethanol, and slightly soluble in methanol.
Benznidazole Tablets are white round tablets each containing 12.5 mg or 100 mg of benznidazole, for oral use. The 100 mg white tablets are round and functionally scored twice as a cross on both sides debossed with “E” on one side of each quarter portion. The 12.5 mg white tablets are round and unscored debossed with “E” on one side.
The inactive ingredients are as follows: magnesium stearate, NF; microcrystalline cellulose, NF; monohydrate lactose, NF; pre-gelatinized corn starch, NF; and sodium croscarmellose, NF.
Benznidazole Tablets are indicated in pediatric patients 2 to 12 years of age for the treatment of Chagas disease (American trypanosomiasis) caused by Trypanosoma cruzi.
This indication is approved under accelerated approval based on the number of treated patients who became Immunoglobulin G (IgG) antibody negative against the recombinant antigens of T. cruzi [see Clinical Studies]. Continued approval for this indication may be contingent upon verification and description of clinical benefit in confirmatory trials.
The total daily dose for pediatric patients 2 to 12 years of age is 5 mg/kg to 8 mg/kg orally administered in two divided doses separated by approximately 12 hours, for a duration of 60 days (see Table 1).
Table 1: Recommended Dosage of Benznidazole Tablets in Pediatric Patients (2 to 12 Years of Age)
| Body Weight Range (kg) | Dose (mg) | Number of Benznidazole Tablets 12.5 mg | Number of Benznidazole Tablets 100mg | Duration and Frequency of Therapy |
| Less than 15 kg | 50 mg | 4 tablets | ½ tablet | Administered twice daily approximately 12 hours apart for 60 days. |
| 15 kg to less than 20 kg | 62.5 mg | 5 tablets | ||
| 20 kg to less than 30 kg | 75 mg | 6 tablets | ¾ tablet | |
| 30 kg to less than 40 kg | 100 mg | 1 tablet | ||
| 40 kg to less than 60 kg | 150 mg | 1 ½ tablets | ||
| Greater than or equal to 60 kg | 200 mg | 2 tablets |
Obtain a pregnancy test in females of reproductive potential prior to therapy with Benznidazole Tablets [see Use In Specific Populations].
Benznidazole Tablets 12.5 mg may be made into slurry in a specified volume of water for the pediatric population with body weight less than 30 kg (see Table 2). The 12.5 mg tablet slurry is prepared by the following method:
Table 2: Preparation and Administration of Slurry Using Benznidazole Tablets 12.5 mg for the Pediatric Population with Body Weight of Less than 30 kg
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| Body Weight Range (kg) | Dose (mg) | Number of Benznidazole Tablets 12.5 mg | Quantity of Water for Preparing the Slurry |
| Less than 15 kg | 100 mg | 4 tablets | 40 mL |
| 15 kg to less than 20 kg | 62.5 mg | 5 tablets | 50 mL |
| 20 kg to less than 30 kg | 75 mg | 6 tablets | 60 mL |
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Benznidazole Tablets 100 mg may be made into a slurry in a specified volume of water for the pediatric population with body weight of 30 kg or greater (see Table 3). The 100 mg tablet slurry is prepared as follows:
Table 3: Preparation and Administration of Slurry Using Benznidazole Tablets 100 mg for the Pediatric Population with Body Weight 30 kg or greater
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| Body Weight Range (kg) | Dose (mg) | Number of Benznidazole Tablets 100 mg | Quantity of Water for Preparing the Slurry |
| 30 kg to less than 40 kg | 100 mg | 1 tablet | 80 mL |
| 40 kg to less than 60 kg | 150 mg | 1 ½ tablets | 120 mL |
| Greater than or equal to 60 kg | 200 mg | 2 tablets | 160 mL |
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Benznidazole Tablets are available as 100 mg and 12.5 mg tablets.
The 100 mg white tablets are round and functionally scored twice as a cross on both sides, debossed with “E” on one side of each quarter portion.
The 12.5 mg white tablets are round and unscored, debossed with “E” on one side.
Benznidazole Tablets (12.5 mg or 100 mg) are supplied as follows:
Benznidazole Tablets 100 mg are available in bottles of 100 tablets (NDC 0642-7464-10).
Benznidazole Tablets 12.5 mg are available in bottles of 100 tablets (NDC 0642-7463-12).
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) [See USP Controlled Room Temperature]. Keep bottle tightly closed and protect from moisture.
REFERENCES
1. Sosa Estani S, et al., 1998, Efficacy of Chemotherapy with Benznidazole in Children in the Indeterminate Phase of Chagas’ Disease. Am J Trop Med Hyg 59: 526-529.
2. de Andrade, Ana Lucia S. Sgambatti, et al., 1996, Randomised Trial of Efficacy of Benznidazole in Treatment of Early Trypanosoma cruzi Infection. Lancet 348: 1407-1413.
3. Altcheh, Jaime, et al., 2014, Population Pharmacokinetic Study of Benznidazole in Pediatric Chagas Disease Suggests Efficacy Despite Lower Plasma Concentrations than in Adults. PLoS Negl Trop Dis 8:e2907.
4. García-Bournissen, F, S Moroni, ME Marson, et al., 2015, Limited Infant Exposure to Benznidazole Through Breast Milk During Maternal Treatment for Chagas Disease. Arch Dis Child 100:90-94.
Manufactured by: Laboratorios Liconsa S.A., Guadalajara, Spain. Revised: Aug 2017
The following serious and otherwise important adverse reactions are discussed in greater detail in other sections of labeling:
Because clinical trials are conducted under widely varying conditions, adverse reaction rates observed in the clinical trials of a drug cannot be directly compared to rates in the clinical trials of another drug and may not reflect the rates observed in practice.
Benznidazole was evaluated in two randomized, double-blind, placebo-controlled trials (Tril 11 and Trial 22) and one uncontrolled trial (Trial 33).
Trial 1 was conducted in pediatric patients 6 to 12 years of age with chronic indeterminate Chagas disease in Argentina. The chronic indeterminate form includes patients with serologic evidence of T. cruzi infection without symptoms of cardiac or gastrointestinal disease. A total of 106 patients were randomized to receive either benznidazole (5 mg/kg/day twice daily for 60 days; N= 55) or placebo (N=51) and followed for 4 years.
Trial 2 was conducted in pediatric patients 7 to 12 years of age with chronic indeterminate Chagas disease in Brazil. A total of 129 patients were randomized to receive either benznidazole (7.5 mg/kg/day twice daily for 60 days; N = 64) or placebo (N = 65) and followed for 3 years.
Trial 3 was an uncontrolled study in pediatric patients 2 to 12 years of age with chronic indeterminate Chagas disease. A total of 37 pediatric patients with Chagas disease were enrolled in this safety and pharmacokinetics study. Patients were treated with benznidazole 5 to 8 mg/kg/day twice daily for 60 days.
In Trial 1, benznidazole was discontinued due to an adverse reaction in 5/55 (9%) patients. Some patients had more than one adverse reaction resulting in treatment discontinuation. The adverse reactions included abdominal pain, nausea, vomiting, rash, decreased appetite, headache, and transaminases increased.
The most frequently reported adverse reactions in pediatric patients treated with benznidazole in Trial 1 were abdominal pain (25%), rash (16%), decreased weight (13%), and headache (7%). Table 4 lists adverse reactions occurring at a rate of 1% or greater in pediatric patients with Chagas disease aged 6 to 12 years of age in Trial 1.
Table 4: Adverse Reactions Occurring in Pediatric Patients with Chagas Disease aged 6 to 12 Years in Trial 1
| Body System | Adverse Reaction | Benznidazole (N=55) N (%) |
Placebo (N=51) N (%) |
| Gastrointestinal | Abdominal pain | 14 (25) | 4 (8) |
| Weight decreased | 7 (13) | 1 (2) | |
| Nausea | 3 (5) | 1 (2) | |
| Vomiting | 3 (5) | 0 | |
| Diarrhea | 2 (4) | 0 | |
| Decreased appetite | 3 (5) | 0 | |
| Skin and subcutaneous tissue | Rash | 9 (16) | 0 |
| Metabolism/Laboratory | Transaminases increased | 3 (5) | 0 |
| Nervous system Disorders | Dizziness | 2 (4) | 2 (4) |
| Peripheral neuropathy | 1 (2) | 0 | |
| Tremor | 1 (2) | 0 |
In Trial 2, skin lesions were reported in 7 of 64 (11%) pediatric patients treated with benznidazole and in 2 of 65 patients receiving placebo. Adverse reactions reported in fewer than 5% of benznidazole-treated patients included nausea, anorexia, headache, abdominal pain and arthralgia.
In a subset of 19 pediatric patients 2 to 6 years of age treated with benznidazole in Trial 3, 6 patients (32%) had the following adverse reactions: rash, leukopenia, urticaria, eosinophilia, decreased appetite, and neutropenia. These adverse reactions were similar to those observed in the overall population of 37 patients.
The following adverse reactions have been identified during the use of other formulations of benznidazole outside of the United States. Because these reactions are reported from a population of uncertain size, it is not always possible to reliably estimate their frequency or establish a causal relationship to drug exposure.
Table 5: Adverse Reactions Reported in the Published Literature
| Body System | Adverse Reactions |
| Dermatological |
|
| Neurological (central and peripheral nervous system) |
|
| Gastrointestinal |
|
| Hepatobiliary disorders |
|
| Skeletal Muscle |
|
| General / Constitutional Symptoms |
|
| Lymphatic |
|
| Bone Marrow |
|
| Metabolism / Laboratory |
|
Psychotic reactions have been reported in patients who are concurrently taking disulfiram and nitroimidazole agents (structurally related to benznidazole, but not with benznidazole). Benznidazole Tablets should not be given to patients who have taken disulfiram within the last two weeks [see CONTRAINDICATIONS].
Abdominal cramps, nausea, vomiting, headaches, and flushing may occur if alcoholic beverages or products containing propylene glycol are consumed during or following therapy with nitroimidazole agents which are structurally related to benznidazole. Although no similar reactions have been reported with benznidazole, discontinue alcoholic beverage or products containing propylene glycol during and for at least 3 days after therapy with Benznidazole Tablets [see CONTRAINDICATIONS].
Included as part of the "PRECAUTIONS" Section
Genotoxicity of benznidazole has been demonstrated in humans, in vitro in several bacterial species and mammalian cell systems, and in vivo in rodents [see Nonclinical Toxicology].
A study evaluating the cytogenetic effect of benznidazole in pediatric patients ranging from 11 months to 11 years of age (the safety and effectiveness of Benznidazole Tablets in patients less than 2 years old has not been established) with Chagas disease demonstrated a two-fold increase in chromosomal aberrations. In pediatric patients with Chagas disease who were treated with benznidazole, the median incidence of micronucleated interphase lymphocytes in 20 patients increased 2 fold compared to pre-dose values. In the same study, the mean incidence of chromosomal aberrations in 10 patients also increased 2 fold compared to pre-dose values.
Carcinogenicity has been observed in mice and rats treated chronically with nitroimidazole agents which are structurally similar to benznidazole. Similar data have not been reported for benznidazole [see Nonclinical Toxicology]. It is not known whether benznidazole is associated with carcinogenicity in humans.
Based on findings from animal studies, Benznidazole Tablets can cause fetal harm when administered to a pregnant woman. In animal reproduction studies, benznidazole administered orally to pregnant rats and rabbits during organogenesis was associated with fetal malformations at doses approximately 1-3 times the maximum recommended human dose (MRHD) in rats (anasarca, anophthalmia, and/or microphthalmia) and doses approximately 0.3-1 times the MRHD in rabbits (ventricular septal defect). In rats, reduced maternal weights and smaller litter sizes occurred at a dose approximately 3 times the MRHD. In rabbits, reduced maternal weight gain, and abortions in 2/20 females occurred at a dose approximately equal to the MHRD [see Use In Specific Populations]. Advise pregnant women of the potential risk to a fetus. Pregnancy testing is recommended for females of reproductive potential [see DOSAGE AND ADMINISTRATION]. Advise females of reproductive potential to use effective contraception during treatment with Benznidazole Tablets and for 5 days after the last dose [see Use In Specific Populations and CLINICAL PHARMACOLOGY].
Serious skin and subcutaneous disorders including acute generalized exanthematous pustulosis (AGEP), toxic epidermal necrolysis (TEN), erythema multiforme, and eosinophilic drug reaction have been reported with benznidazole. Discontinue treatment at the first evidence of these serious cutaneous reactions [see ADVERSE REACTIONS].
Extensive skin reactions, such as rash (maculopapular, pruritic macules, eczema, pustules, erythematous, generalized, and allergic dermatitis, exfoliative dermatitis) have also been reported. Most cases occurred after approximately 10 days of treatment with benznidazole. Most rashes resolved with treatment discontinuation.
In case of skin reactions presenting with additional symptoms or signs of systemic involvement such as lymphadenopathy, fever and/or purpura, discontinuation of treatment is recommended.
Treatment with Benznidazole Tablets can cause paresthesia or symptoms of peripheral neuropathy that may take several months to resolve. Headache and dizziness have been reported. In cases where neurological symptoms occur, immediate discontinuation of treatment is recommended. In most cases, symptoms occur late in the course of treatment.
There have been reports of hematological manifestations of bone marrow depression, such as neutropenia, thrombocytopenia, anemia and leukopenia, which resolved after treatment discontinuation [see ADVERSE REACTIONS]. Patients with hematological manifestations of bone marrow depression must take Benznidazole Tablets only under strict medical supervision. Monitor complete blood count. Total and differential leukocyte counts are recommended before, during and after therapy.
Long-term carcinogenicity studies for benznidazole have not been performed.
Nitroimidazoles, which have similar chemical structures to benznidazole have been reported to be carcinogenic in mice and rats.
Genotoxicity of benznidazole has been demonstrated in vitro in several bacterial species and mammalian cell systems and in vivo in mammals.
Benznidazole was mutagenic in several strains of S. typhimurium (TA 100, 102 1535, 1537, 1538, 97, 98 99 53 and UTH8414), E.coli, and K. pneumoniae.
Benznidazole was genotoxic in several in vitro mammalian cell assays including a chromosome aberration assay in human lymphocytes and in sister chromatid exchange assays in human lymphocytes and in Human Hep G2 cells
In vivo, benznidazole was shown to be positive for genotoxicity in a mouse bone marrow micronucleus assay, in mouse and human red blood cell micronucleus assays, in a mouse abnormal sperm head assay and in a human peripheral blood lymphocyte assay. However in other micronucleus studies in mice and rats, oral doses of benznidazole did not cause a significant increase in the frequency of chromosomal aberrations in bone marrow cells or micronuclei in peripheral blood cells.
In a 6-month, chronic repeated-dosing study with Wistar rats, benznidazole was shown to produce dose-dependent testicular and epididymal atrophy at a dose of 30 mg/kg/day (approximately equivalent to 0.6 times the MRHD based on whole body surface area comparisons). Aspermia was also evident in affected rats, but fertility was not assessed in this study. The NOAEL value in this study was considered to be 10 mg/kg/day (5 mg/kg twice daily) in males which is approximately 0.2-times the MRHD based on body surface area comparison. In other literature reports, benznidazole has been shown to cause testicular atrophy and inhibit spermatogenesis in pubertal and adult rats and mice5-7 .
In a female fertility study, oral (gavage) administration of benznidazole to female Wistar rats twice daily for a 2-week pre-mating period, during mating, and through day 7 of gestation was associated with transient lower body weight gain and food consumption. There was no benznidazole-related effect on mating performance or fertility and no adverse macroscopic or reproductive organ weight changes. However, benznidazole reproductive performance was associated with a higher post-implantation loss with lower live litter size at a dose of 150 mg/kg/day (equivalent to approximately 3 times the MRHD based on whole body surface area comparisons). The NOAEL value for this study was considered to be 50 mg/kg/day which is approximately equivalent to the MRHD based on whole body surface area comparison.
Based on findings from animal studies, Benznidazole Tablets may cause fetal harm when administered to a pregnant woman. Published postmarketing reports on benznidazole use during pregnancy are insufficient to inform a drug-associated risk of adverse pregnancy-related outcomes. There are risks to the fetus associated with Chagas Disease (see Clinical Considerations). In animal reproduction studies, benznidazole administered orally to pregnant rats and rabbits during organogenesis was associated with fetal malformations at doses approximately 1-3 times the MRHD in rats (anasarca, anophthalmia, and/or microphthalmia) and doses approximately 0.3-1.0 times the MRHD in rabbits (ventricular septal defect) (see Data). Advise pregnant women of the potential risk to a fetus.
The estimated background risk of major birth defects and miscarriage for the indicated population is unknown. All pregnancies have a background risk of birth defect, loss, or other adverse outcomes. In the U.S. general population, the estimated background risk of major birth defects and miscarriage in clinically recognized pregnancies is 2-4% and 15-20%, respectively.
Disease-associated Maternal and/or Embryo/Fetal Risk
Published data from case-control and observational studies on chronic Chagas disease during pregnancy are inconsistent in their findings. Some studies showed an increased risk of pregnancy loss, prematurity and neonatal mortality in pregnant women who have chronic Chagas disease while other studies did not demonstrate these findings. Chronic Chagas disease is usually not life-threatening. Since pregnancy findings are inconsistent, treatment of chronic Chagas disease during pregnancy is not recommended due to risk of embryo-fetal toxicity from Benznidazole Tablets.
Acute symptomatic Chagas disease is rare in pregnant women; however, symptoms may be serious or life-threatening. There have been reports of pregnant women with life-threatening symptoms associated with acute Chagas disease who were treated with benznidazole. If a pregnant women presents with acute symptomatic Chagas disease, the risks versus benefits of treatment with Benznidazole Tablets to the mother and the fetus should be evaluated on a case-by-case basis.
Animal Data
In an embryo-fetal toxicity study in pregnant rats, an oral dose of benznidazole of 150 mg/kg/day during organogenesis (days 6-17 of gestation) was associated with maternal weight loss, reduced fetal weights, and smaller litter sizes. Benznidazole was also associated with a low incidence of fetal malformations including anasarca in one fetus at a dose of 50 mg/kg/day and anasarca and eye abnormalities (anophthalmia and microphthalmia) in 5 fetuses in 5 litters at a high dose of 150 mg/kg/day (approximately equivalent to 1 and 3 times, respectively, the MRHD based on whole body surface area comparisons). The No Observed Adverse Effect Level (NOAEL) dose for maternal toxicity in this study, 50 mg/kg/day, is approximately equal to the MRHD based on body surface area comparisons. The NOAEL dose for fetal toxicity was 15 mg/kg/day which is approximately equivalent to 0.3 times the MRHD based on whole body surface area comparisons.
In an embryo-fetal study in pregnant rabbits, oral (gavage) administration of benznidazole during organogenesis (days 6 to 19 of gestation) at a high dose of 25 mg/kg/day was associated with maternal toxicity including reduced weight gain and food consumption and abortions in 2/20 females. Benznidazole was also associated with a low incidence of fetal abnormalities including ventricular septal defect in 2 fetuses in 2 litters at a dose of 7.5 mg/kg/day and in 1 fetus at a dose of 25 mg/kg/day (approximately equivalent to 0.3 and 1 times respectively the MRHD based on whole body surface area comparisons). The NOAEL values for maternal and fetal toxicity in this study were 7.5 and 2.5 mg/kg/day respectively, which are respectively equivalent to approximately 0.3 and 0.1 times the MRHD based on body surface area comparisons.
In a pre-postnatal study in rats, first generation (F1) pups born to dams administered 15, 50, and 75 mg/kg/day benznidazole demonstrated normal pre-weaning behavior, physical and functional development, neurological findings, and reproductive parameters. However, cesarean section data for the pregnant first generation (F1) females in the high-dose group included significantly higher pre-implantation loss and significantly lower mean values for corpora lutea counts, number of implantations, and number of live embryos. Also small testes and/or epididymides were observed in 1/20 and 2/20 first generation males in the mid-and high-dose groups respectively, and two of the affected animals failed to mate or induce pregnancy. However, the mean values for mating performance, fertility index, testes weight, testes and epididymides sperm counts, and epididymal sperm motility and progression were not altered in any of the F1 males in benznidazole treatment groups. The number of live second generation (F2) fetuses born to F1 dams was reduced in the high-dose group. The NOAEL value was considered to be 50 mg/kg/day which is approximately equal to the MRHD based on body surface area comparisons.
Limited published literature based on breast milk sampling reports that benznidazole is present in human milk at infant doses of 5.5 to 17% of the maternal weight-adjusted dosage and a milk/plasma ratio ranging between 0.32.79. There are no reports of adverse effects on the breastfed infant and no information on the effects of benznidazole on milk production. Because of the potential for serious adverse reactions, and transmission of Chagas disease, advise patients that breastfeeding is not recommended during treatment with Benznidazole Tablets.
Pregnancy testing is recommended for females of reproductive potential.
Females
Benznidazole Tablets can cause fetal harm when administered to a pregnant woman [see Pregnancy]. Advise females of reproductive potential to use effective contraception during treatment with Benznidazole Tablets and for 5 days after the final dose.
Males
Based on findings in rodents, Benznidazole Tablets may impair fertility in males of reproductive potential. It is not known whether effects on fertility are reversible [see Nonclinical Toxicology].
The safety and effectiveness of Benznidazole Tablets have been established in pediatric patients 2 to 12 years of age for the treatment of Chagas disease. Use in pediatric patients 2 to 12 years of age was established in two adequate and well-controlled trials in pediatric patients 6 to 12 years old with additional safety and pharmacokinetic data from pediatric patients 2 to 6 years of age. [see DOSAGE AND ADMINISTRATION , ADVERSE REACTIONS , Clinical Studies].
Safety and effectiveness in pediatric patients below the age of 2 years and above the age of 12 years have not been established.
Use of Benznidazole Tablets has not been evaluated in patients with hepatic impairment.
Use of Benznidazole Tablets has not been evaluated in patients with renal impairment.
REFERENCES
5. Bernacchi, AS, CR de Castro, EG de Toranzo, and JA Castro, 1986, Effects of Nifurtimox or Benznidazole Administration on Rat Testes: Ultrastructural Observations and Biochemical Studies, Exp Mol Pathol 45: 245-256.
6. Vieira, CL, TL Lamano-Carvalho, AL Favaretto, MM Valenca, J Antunes-Rodridgues, and AA Barreira, 1989, Testes Alterations in Pubertal Benznidazole-treated Rats, Braz J Med Biol Res, 22: 695-698.
7. Navarro, ML and R Nagel, 1990, Abnormal Sperm Induced in Mice by Oral Administration of Antichagasic Drugs, Comunicaciones Biologicas, 8: 251-258.
No Information Provided
Benznidazole Tablets are contraindicated in patients with a history of hypersensitivity reaction to benznidazole or other nitroimidazole derivatives. Reactions have included severe skin and soft tissue reactions [see ADVERSE REACTIONS].
Benznidazole Tablets are contraindicated in patients who have taken disulfiram within the last two weeks. Psychotic reactions may occur in patients who are using benznidazole and disulfiram concurrently [see DRUG INTERACTIONS].
Consumption of alcoholic beverages or products containing propylene glycol is contraindicated in patients during and for at least 3 days after therapy with Benznidazole Tablets. A disulfiram-like reaction (abdominal cramps, nausea, vomiting, headaches, and flushing) may occur due to the interaction between alcohol or propylene glycol and benznidazole [see DRUG INTERACTIONS].
Benznidazole is a nitroimidazole antimicrobial drug [see Microbiology].
The pharmacodynamics of benznidazole is unknown.
The absorption of benznidazole from three different 100 mg benznidazole preparations was comparable when administered as a single dose under fasting conditions in adult healthy volunteers (Table 6).
Table 6: Summary of Benznidazole Pharmacokinetic (PK) Parameters Following a Single Oral Dose of 100 mg Benznidazole Administered Under Fasting Conditions in Adult Healthy Volunteers
| Preparations for 100 mg Benznidazole Oral Dose | |||
| One Benznidazole 100 mg Tablets Taken Whole | Slurry prepared with one Benznidazole 100 mg Tablet | Slurry prepared with eight Benznidazole12.5 mg Tablets | |
| Parameter | Mean (SD) | Mean (SD) | Mean (SD) |
| Cmax (mg/L) | 2.4 (0.5) | 2.4 (0.4) | 2.4 (0.4) |
| Tmaxa (h) | 2 (1 – 4) | 2 (0.5 – 4) | 2 (1 – 4.5) |
| AUC (mg*h/L) | 43.5 (9.0) | 41.8 (9.6) | 44.1 (11.8) |
| aTmax is presented as median (range) | |||
Effect of Food
Benznidazole Cmax and AUC were not affected by the administration of Benznidazole 100 mg tablet with a high-fat, high-caloric meal (approximately 1034 total kcal, 67 kcal from fat, 42 kcal from carbohydrates, 59 kcal from protein) compared with fasted conditions in adult healthy volunteers. Serum concentrations of benznidazole reached peak levels at 3.2 hours (1-10 hours) after administration of Benznidazole Tablets 100 mg tablet after a high-fat, high-caloric meal, and at 2.0 hours (0.5-4 hours) in fasted conditions [see DOSAGE AND ADMINISTRATION].
Protein binding is reported to be approximately 44 to 60 %.
The elimination half-life of benznidazole is approximately 13 hours in healthy volunteers following single dose.
Metabolism
Benznidazole metabolism pathway is unknown.
Excretion
Benznidazole and unknown metabolites are reported to be excreted in the urine and feces.
The effect of sex, race, renal impairment, or hepatic impairment on the pharmacokinetics of benznidazole is unknown.
In vitro studies showed that benznidazole is a P-gp substrate and does not notably induce Cytochrome P450 enzymes 1A2, 2B6, and 3A4 at concentrations up to 100 uM.
Benznidazole inhibits the synthesis of DNA, RNA, and proteins within the T. cruzi parasite. Studies suggest that benznidazole is reduced by a Type I nitroreductase (NTR) enzyme of T. cruzi producing a series of short-lived intermediates that may promote damage to several macromolecules including DNA. In mammalian cells, however, benznidazole is metabolized by reduction of the nitro group to an amino group by a Type II NTR enzyme. The precise mechanism of action is not known.
Benznidazole is active against all three stages, trypomastigotes, amastigotes, and epimastigotes, of T. cruzi. However, the sensitivity of T. cruzi strains to benznidazole, from different geographic regions, may vary.
Studies in vitro and in mice infected with T. cruzi suggest a potential for development of resistance to benznidazole.
The mechanisms of drug resistance appear to be multifactorial. These mechanisms include decreased activity due to a mutation in the nitroreductase (TcNTR) gene. Other mechanisms include higher efflux activity due to over expression of TcPGP1 and TcPGP2 genes that encode p-glycoprotein as well as TcABCG1 genes that encode ATP-binding cassette transporters. Also, some studies reported overexpression of other genes TcFeSOD-A and TcCyP19 that encode superoxide dismutase and cyclophilin, respectively, which have diverse biological function and may help parasite survival. However, the clinical relevance of these findings is not known.
Single oral-dose toxicity studies in rats have established that benznidazole causes ultrastructural changes in the adrenal cortex, colon, esophagus, ovaries, and testis 5, 8-11In these tissues, the changes were associated with the presence of nitro reductase activity, the production of reactive metabolites, and/or covalent binding of metabolites.
Neurotoxicity including brain axonal degeneration and Purkinje cell degeneration was observed with repeated-oral dosing in dogs without adverse changes in peripheral nerves12-14. Neurological signs included: apathy, hypertonia, hyperreflexia, ataxia, loss of balance, oscillatory movements of the trunk and head, strong contractions of the back and leg muscles, opisthotonus and nystagmus. Neurotoxicity was not observed in other test species, including mouse, rat, guinea pig, and rabbit.
The safety and effectiveness of benznidazole for the treatment of Chagas disease in patients 6 to 12 years of age was established in two adequate and well-controlled trials (Trial 1 and Trial 2) as described below.
Trial 1 was a randomized, double-blind, placebo-controlled trial in children 6 to 12 years of age with chronic indeterminate Chagas disease conducted in Argentina. The chronic indeterminate form of Chagas disease includes patients with serologic evidence of T. cruzi infection without symptoms of cardiac or gastrointestinal disease. A total of 106 patients were randomized to receive either benznidazole (5 mg/kg/day for 60 days) or placebo and followed for 4 years. Patients with at least two positive conventional serologic tests for antibodies to T. cruzi were included in the study. The conventional serologic tests used include indirect hemagglutination assay (IHA), immunofluorescence antibody assay (IFA), and/or enzyme linked immunosorbent assay (ELISA) and were based on the detection of antibodies against T. cruzi parasites.
Trial 2 was a randomized, double-blind, placebo-controlled trial in pediatric patients 7 to 12 years of age with chronic indeterminate Chagas disease conducted in Brazil. A total of 129 patients were randomized to receive either benznidazole (7.5 mg/kg/day for 60 days) or placebo and followed for 3 years. Patients with three positive conventional serologic tests for antibodies to T. cruzi were included in the study. The conventional serologic tests include IHA, IFA, and/or ELISA and were based on the detection of antibodies against T. cruzi parasites.
Both trials measured antibodies by conventional and nonconventional assays. The nonconventional assays include F29-ELISA and AT-chemiluminescence-ELISA that are based on detection of anti-T. cruzi IgG antibodies against the recombinant antigens, F29 and AT from the flagella of T. cruzi parasites. Benznidazole treatment resulted in a significantly higher percentage of seronegative patients by a nonconventional assay. Results at the end of follow-up are reported in the following table.
Table 7. Nonconventional ELISAa Serologic Status at End-of-Follow-Up (mITT populationb)
| Benznidazole | Placebo | Difference (95% CI)c | |
| Trial 1 | N=40 | N=37 | |
| Seronegative | 24 (60.0) |
5 (13.5) |
46.5 (24.5, 64.4) |
| Seropositive | 15 | 29 | |
| Missing | 1 | 3 | |
| Trial 2 | N=64 | N=65 | |
| Seronegative | 35 (54.7) |
3 (4.6) |
50.1 (35.8, 63.4) |
| Seropositive | 23 | 51 | |
| Missing | 6 | 11 | |
| aEnzyme-linked immunosorbent assay (F29 ELISA in Study Trial 1 and AT chemiluminescence-ELISA in Trial 2); the F29 and AT antigens represent antigens from the flagella of T. cruzi parasites. bModified intent to treat (mITT) population includes subjects who are positive for the assay at baseline; cExact confidence intervals presented. |
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In Trial 1 using conventional ELISA, 4 of 53 (7.5%) benznidazole subjects and 2 of 50 (4.0%) placebo subjects seroconverted to negative by the end of follow-up (difference 3.5, 95% CI (-7.0, 14.9)). In Trial 2 using conventional ELISA, 4 of 64 (6.3%) of benznidazole subjects and 0 of 65 placebo subjects seroconverted to negative by the end of follow-up (difference 6.3, 95% CI (0.3, 15.2)).
REFERENCES
5. Bernacchi, AS, CR de Castro, EG de Toranzo, and JA Castro, 1986, Effects of Nifurtimox or Benznidazole Administration on Rat Testes: Ultrastructural Observations and Biochemical Studies, Exp Mol Pathol 45: 245-256.
8. de Castro, RC, EG Diaz de Toranzo, and JA Castro, 1992, Benznidazole-induced Ultrastructural Alterations in Rat Adrenal Cortex: Mechanistic Studies, Toxicology, 74: 223-232.
9. Diaz, EG, RC de Castro, M Montalto de Mecca, and JA Castro, 2000, Benznidazole-induced Ultrastructural and Biochemical Alterations in Rat Colon, Acta Pharmacol Sin, 21: 961-966.
10. de Castro, RC, M Montalto de Mecca, SL Fanelli, EC de Ferreyra, EG Diaz, and JA Castro, 2003, Benznidazole-induced Ultrastructural and Biochemical Alterations in Rat Esophagus, Toxicology, 191: 189198.
11. de Castro, CR, EGD de Toranzo, AS Bernacchi, M Carbone, and JA Castro, 1989, Ultrastructural Alterations in Ovaries from Nifurtimox or Benznidazole-treated Rats: Their Relation to Ovarian Nitroreductive Biotransformation of Both Drugs, Exp Mol Pathol, 50: 385-397.
12. Scharer, K, 1972, Selective Purkinje Cell Damage in Dogs after Oral Administration of High Doses of Nitroimidazole Derivatives, Verhandlungen der Deutschen Gesellschaft fur Pathologie, 56: 407-10.
13. Flores-Vieira, CLL and AA Barreira, 1997a, Experimental Benznidazole Encephalopathy: I. Clinical-Neurological Alterations, J Neurol Sci, 150: 3-11.
14. Flores-Vieira, CLL, L Chimelli, RMF Fernandez, and AA Barreira, 1997b, Experimental Benznidazole Encephalopathy: II. Electroencephalographic and Morphological Alterations, J Neurol Sci, 150:13-25.
Advise the patient to read the FDA-approved patient labeling (Instructions for Use).
Advise pregnant women and females of reproductive potential that exposure to Benznidazole Tablets during pregnancy can result in fetal harm. Advise females to inform their healthcare provider of a known or suspected pregnancy [see WARNINGS AND PRECAUTIONS and Use In Specific Populations].
Advise females of reproductive potential to use effective contraception while taking Benznidazole Tablets and for 5 days after the last dose [see Use In Specific Populations].
Advise women not to breastfeed during treatment with Benznidazole Tablets [see Use In Specific Populations].
Advise males of reproductive potential that Benznidazole Tablets may impair fertility [see Use In Specific Populations and Nonclinical Toxicology].
Advise patients and parents/caregivers of pediatric patients taking Benznidazole Tablets that:
Advise patients that serious skin reactions can occur with Benznidazole Tablets. In case of skin reactions, presenting with additional symptoms of systemic involvement such as lymphadenopathy, fever and/or purpura, discontinuation of treatment is necessary.
Advise patients that treatment can potentially cause paresthesia or symptoms of peripheral neuropathy. In cases where neurological symptoms occur, immediate discontinuation of treatment is recommended.
Advise patients that there have been hematological manifestations of bone marrow depression, such as anemia and leukopenia, which are reversible, and normalized after treatment discontinuation.
Advise patients to discontinue consumption of alcoholic beverages or products containing propylene glycol while taking Benznidazole Tablets and for at least three days afterward because abdominal cramps, nausea, vomiting, headaches, and flushing may occur.
INSTRUCTIONS FOR USE
BENZNIDAZOLE
tablets, for oral use
Read this Instructions for Use before you start taking BENZNIDAZOLE and each time you get a refill. There may be new information. This information does not take the place of talking to your doctor about your medical condition or treatment.
Note:
100 mg treatment (take the whole tablet)
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Full tablet side view
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How to break your BENZNIDAZOLE 100 mg tablet:
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75 mg treatment (take one-half of the tablet and one-fourth of the tablet)
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50 mg treatment (take one-half of the tablet)
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One half-tablet top view
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25 mg treatment (take one-fourth of the tablet)
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How should I store BENZNIDAZOLE?
Keep BENZNIDAZOLE and all medicines out of the reach of children.
This Instructions for Use has been approved by the U.S. Food and Drug Administration.
