Albenza Tablets (Glaxosmithkline)

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DESCRIPTION

Albenza (albendazole) is an orally administered broad-spectrum anthelmintic. Chemically it is Methyl 5-(propyl-thio)-2-benzimidazolecarbamate. Its molecular formula is C ₁₂ H ₁₅ N ₃ O ₂ S. Its molecular weight is 265.34.

Albendazole is a white to off-white powder. It is soluble in dimethylsulfoxide, strong acids and strong bases. It is slightly soluble in methanol, chloroform, ethyl acetate and acetonitrile. Albendazole is practically insoluble in water. Each white to off-white, film-coated tablet contains 200 mg of albendazole.

Inactive ingredients consist of: carnauba wax, hydroxypropyl methylcellulose, lactose monohydrate, magnesium stearate, microcrystalline cellulose, povidone, sodium lauryl sulfate, sodium saccharin, sodium starch glycolate, and starch.

CLINICAL PHARMACOLOGY

Pharmacokinetics

Absorption and Metabolism

Albendazole is poorly absorbed from the gastrointestinal tract due to its low aqueous solubility. Albendazole concentrations are negligible or undetectable in plasma as it is rapidly converted to the sulfoxide metabolite prior to reaching the systemic circulation. The systemic anthelmintic activity has been attributed to the primary metabolite, albendazole sulfoxide. Oral bioavailability appears to be enhanced when albendazole is coadministered with a fatty meal (estimated fat content 40 g) as evidenced by higher (up to 5-fold on average) plasma concentrations of albendazole sulfoxide as compared to the fasted state.

Maximal plasma concentrations of albendazole sulfoxide are typically achieved 2 to 5 hours after dosing and are on average 1.31 mcg/mL (range 0.46 to 1.58 mcg/mL) following oral doses of albendazole (400 mg) in six hydatid disease patients, when administered with a fatty meal. Plasma concentrations of albendazole sulfoxide increase in a dose-proportional manner over the therapeutic dose range following ingestion of a fatty meal (fat content 43.1 g). The mean apparent terminal elimination half-life of albendazole sulfoxide typically ranges from 8 to 12 hours in twenty-five normal subjects, as well as in fourteen hydatid and eight neurocysticercosis patients.

Following 4 weeks of treatment with albendazole (200 mg three times daily), twelve patients' plasma concentrations of albendazole sulfoxide were approximately 20% lower than those observed during the first half of the treatment period, suggesting that albendazole may induce its own metabolism.

Distribution

Albendazole sulfoxide is 70% bound to plasma protein and is widely distributed throughout the body; it has been detected in urine, bile, liver, cyst wall, cyst fluid, and cerebral spinal fluid (CSF). Concentrations in plasma were 3- to 10-fold and 2- to 4-fold higher than those simultaneously determined in cyst fluid and CSF, respectively. Limited in vitro and clinical data suggest that albendazole sulfoxide may be eliminated from cysts at a slower rate than observed in plasma.

Metabolism and Excretion

Albendazole is rapidly converted in the liver to the primary metabolite, albendazole sulfoxide, which is further metabolized to albendazole sulfone and other primary oxidative metabolites that have been identified in human urine. Following oral administration, albendazole has not been detected in human urine. Urinary excretion of albendazole sulfoxide is a minor elimination pathway with less than 1% of the dose recovered in the urine. Biliary elimination presumably accounts for a portion of the elimination as evidenced by biliary concentrations of albendazole sulfoxide similar to those achieved in plasma.

Special Populations

Patients with Impaired Renal Function:   The pharmacokinetics of albendazole in patients with impaired renal function have not been studied. However, since renal elimination of albendazole and its primary metabolite, albendazole sulfoxide, is negligible, it is unlikely that clearance of these compounds would be altered in these patients.

Biliary Effects:   In patients with evidence of extrahepatic obstruction (n=5), the systemic availability of albendazole sulfoxide was increased, as indicated by a 2-fold increase in maximum serum concentration and a 7-fold increase in area under the curve. The rate of absorption/conversion and elimination of albendazole sulfoxide appeared to be prolonged with mean T _max and serum elimination half-life values of 10 hours and 31.7 hours, respectively. Plasma concentrations of parent albendazole were measurable in only one of five patients.

Pediatrics:   Following single-dose administration of 200 mg to 300 mg (approximately 10 mg/kg) albendazole to three fasted and two fed pediatric patients with hydatid cyst disease (age range 6 to 13 years), albendazole sulfoxide pharmacokinetics were similar to those observed in fed adults.

Elderly Patients:   Although no studies have investigated the effect of age on albendazole sulfoxide pharmacokinetics, data in twenty-six hydatid cyst patients (up to 79 years) suggest pharmacokinetics similar to those in young healthy subjects.

Microbiology

The principal mode of action for albendazole is by its inhibitory effect on tubulin polymerization which results in the loss of cytoplasmic microtubules.

In the specified treatment indications albendazole appears to be active against the larval forms of the following organisms:

Echinococcus granulosus

Taenia solium

INDICATIONS AND USAGE

Albenza (albendazole) is indicated for the treatment of the following infections:

Neurocysticercosis.    Albenza is indicated for the treatment of parenchymal neurocysticercosis due to active lesions caused by larval forms of the pork tapeworm, Taenia solium .

Lesions considered responsive to albendazole therapy appear as nonenhancing cysts with no surrounding edema on contrast-enhanced computerized tomography. Clinical studies in patients with lesions of this type demonstrate a 74% to 88% reduction in number of cysts; 40% to 70% of albendazole-treated patients showed resolution of all active cysts.

Hydatid disease.    Albenza is indicated for the treatment of cystic hydatid disease of the liver, lung, and peritoneum, caused by the larval form of the dog tapeworm, Echinococcus granulosus .

This indication is based on combined clinical studies which demonstrated non-infectious cyst contents in approximately 80-90% of patients given Albenza for 3 cycles of therapy of 28 days each. (See DOSAGE AND ADMINISTRATION .) Clinical cure (disappearance of cysts) was seen in approximately 30% of these patients, and improvement (reduction in cyst diameter of >/=25%) was seen in an additional 40%.

NOTE: When medically feasible, surgery is considered the treatment of choice for hydatid disease. When administering Albenza in the pre- or post-surgical setting, optimal killing of cyst contents is achieved when three courses of therapy have been given.

NOTE: The efficacy of albendazole in the therapy of alveolar hydatid disease caused by Echinococcus multilocularis has not been clearly demonstrated in clinical studies.

CONTRAINDICATIONS

Albenza (albendazole) is contraindicated in patients with known hypersensitivity to the benzimidazole class of compounds or any components of Albenza .

WARNINGS

Rare fatalities associated with the use of Albenza have been reported due to granulocytopenia or pancytopenia. (See PRECAUTIONS .) Blood counts should be monitored at the beginning of each 28-day cycle of therapy, and every 2 weeks while on therapy with albendazole. Albendazole may be continued if the total white blood cell count and absolute neutrophil count decrease appear modest and do not progress.

Albendazole should not be used in pregnant women except in clinical circumstances where no alternative management is appropriate. Patients should not become pregnant for at least 1 month following cessation of albendazole therapy. If a patient becomes pregnant while taking this drug, albendazole should be discontinued immediately. If pregnancy occurs while taking this drug, the patient should be apprised of the potential hazard to the fetus.

PRECAUTIONS

General: Patients being treated for neurocysticercosis should receive appropriate steroid and anticonvulsant therapy as required. Oral or intravenous corticosteroids should be considered to prevent cerebral hypertensive episodes during the first week of anticysticeral therapy.

Cysticercosis may, in rare cases, involve the retina. Before initiating therapy for neurocysticercosis, the patient should be examined for the presence of retinal lesions. If such lesions are visualized, the need for anticysticeral therapy should be weighed against the possibility of retinal damage caused by albendazole-induced changes to the retinal lesion.

Information for Patients

Patients should be advised that:

• Albendazole may cause fetal harm, therefore, women of childbearing age should begin treatment after a negative pregnancy test.
• Women of childbearing age should be cautioned against becoming pregnant while on albendazole or within 1 month of completing treatment.
• During albendazole therapy, because of the possibility of harm to the liver or bone marrow, routine (every 2 weeks) monitoring of blood counts and liver function tests should take place.
• Albendazole should be taken with food.

Laboratory Tests

White Blood Cell Count: Albendazole has been shown to cause occasional (less than 1% of treated patients) reversible reductions in total white blood cell count. Rarely, more significant reductions may be encountered including granulocytopenia, agranulocytosis, or pancytopenia. Blood counts should be performed at the start of each 28-day treatment cycle and every 2 weeks during each 28-day cycle. Albendazole may be continued if the total white blood cell count decrease appears modest and does not progress.

Liver Function: In clinical trials, treatment with albendazole has been associated with mild to moderate elevations of hepatic enzymes in approximately 16% of patients. These have returned to normal upon discontinuation of therapy.

Liver function tests (transaminases) should be performed before the start of each treatment cycle and at least every 2 weeks during treatment. If enzymes are significantly increased, albendazole therapy should be discontinued. Therapy can be reinstituted when liver enzymes have returned to pretreatment levels, but laboratory tests should be performed frequently during repeat therapy.

Patients with abnormal liver function test results prior to commencing albendazole therapy should be carefully evaluated, since the drug is metabolized by the liver and has been associated with hepatotoxicity in a few patients.

Theophylline: Although single doses of albendazole have been shown not to inhibit theophylline metabolism (see Drug Interactions ), albendazole does induce cytochrome P450 1A in human hepatoma cells. Therefore, it is recommended that plasma concentrations of theophylline be monitored during and after treatment with Albenza (albendazole).

Drug Interactions

Dexamethasone: Steady-state trough concentrations of albendazole sulfoxide were about 56% higher when 8 mg dexamethasone was coadministered with each dose of albendazole (15 mg/kg/day) in eight neurocysticercosis patients.

Praziquantel: In the fed state, praziquantel (40 mg/kg) increased mean maximum plasma concentration and area under the curve of albendazole sulfoxide by about 50% in healthy subjects (n=10) compared with a separate group of subjects (n=6) given albendazole alone. Mean T _max and mean plasma elimination half-life of albendazole sulfoxide were unchanged. The pharmacokinetics of praziquantel were unchanged following coadministration with albendazole (400 mg).

Cimetidine: Albendazole sulfoxide concentrations in bile and cystic fluid were increased (about 2-fold) in hydatid cyst patients treated with cimetidine (10 mg/kg/day) (n=7) compared with albendazole (20 mg/kg/day) alone (n=12). Albendazole sulfoxide plasma concentrations were unchanged 4 hours after dosing.

Theophylline: The pharmacokinetics of theophylline (aminophylline 5.8 mg/kg infused over 20 minutes) were unchanged following a single oral dose of albendazole (400 mg) in 6 healthy subjects.

Carcinogenesis, Mutagenesis, Impairment of Fertility

Long-term carcinogenicity studies were conducted in mice and rats. In the mouse study, albendazole was administered in the diet at doses of 25, 100 and 400 mg/kg/day (0.1, 0.5, and 2 times the recommended human dose based on body surface area in mg/m ² , respectively) for 108 weeks. In the rat study, albendazole was administered in the diet at doses of 3.5, 7, and 20 mg/kg/day (0.04, 0.08, and 0.21 times the recommended human dose based on body surface area in mg/m ² , respectively) for 117 weeks. There was no evidence of increased incidence of tumors in the treated mice and rats when compared to the control group.

In genotoxicity tests, albendazole was found negative in an Ames Salmonella/Microsome Plate mutation assay with and without metabolic activation or with and without pre-incubation, cell-mediated Chinese Hamster Ovary chromosomal aberration test and in vivo mouse micronucleus test. In the in vitro BALB/3T3 cells transformation assay, albendazole produced weak activity in the presence of metabolic activation while no activity was found in the absence of metabolic activation.

Albendazole did not adversely affect male or female fertility in the rat at an oral dose of 30 mg/kg/day (0.32 times the recommended human dose based on body surface area in mg/m ² ).

Pregnancy

Teratogenic Effects-Pregnancy Category C: Albendazole has been shown to be teratogenic (to cause embryotoxicity and skeletal malformations) in pregnant rats and rabbits. The teratogenic response in the rat was shown at oral doses of 10 and 30 mg/kg/day (0.10 times and 0.32 times the recommended human dose based on body surface area in mg/m ² , respectively) during gestation days 6 to 15 and in pregnant rabbits at oral doses of 30 mg/kg/day (0.60 times the recommended human dose based on body surface area in mg/m ² ) administered during gestation days 7 to 19. In the rabbit study, maternal toxicity (33% mortality) was noted at 30 mg/kg/day. In mice, no teratogenic effects were observed at oral doses up to 30 mg/kg/day (0.16 times the recommended human dose based on body surface area in mg/m ² ), administered during gestation days 6 to 15.

There are no adequate and well-controlled studies of albendazole administration in pregnant women.Albendazole should be used during pregnancy only if the potential benefit justifies the potential risk to the fetus. (See WARNINGS .)

Nursing Mothers: Albendazole is excreted in animal milk. It is not known whether it is excreted in human milk. Because many drugs are excreted in human milk, caution should be exercised when albendazole is administered to a nursing woman.

Pediatric Use: Experience in children under the age of 6 years is limited. In hydatid disease, infection in infants and young children is uncommon, but no problems have been encountered in those who have been treated. In neurocysticercosis, infection is more frequently encountered. In five published studies involving pediatric patients as young as 1 year, no significant problems were encountered, and the efficacy appeared similar to the adult population.

Geriatric Use:   Experience in patients 65 years of age or older is limited. The number of patients treated for either hydatid disease or neurocysticercosis is limited, but no problems associated with an older population have been observed.

ADVERSE REACTIONS

The adverse event profile of albendazole differs between hydatid disease and neurocysticercosis. Adverse events occurring with a frequency of >/=1% in either disease are described in the table below.

These symptoms were usually mild and resolved without treatment. Treatment discontinuations were predominantly due to leukopenia (0.7%) or hepatic abnormalities (3.8% in hydatid disease). The following incidence reflects events that were reported by investigators to be at least possibly or probably related to albendazole.

The following adverse events were observed at an incidence of <1%:

Hematologic:   Leukopenia. There have been rare reports of granulocytopenia, pancytopenia, agranulocytosis, or thrombocytopenia. (See WARNINGS .)

Dermatologic:   Rash, urticaria.

Hypersensitivity:   Allergic reactions.

Renal:   Acute renal failure related to albendazole therapy has been observed.

OVERDOSAGE

Significant toxicity and mortality were shown in male and female mice at doses exceeding 5,000 mg/kg; in rats, at estimated doses between 1,300 and 2,400 mg/kg; in hamsters, at doses exceeding 10,000 mg/kg; and in rabbits, at estimated doses between 500 and 1,250 mg/kg. In the animals, symptoms were demonstrated in a dose-response relationship and included diarrhea, vomiting, tachycardia, and respiratory distress.

One overdosage has been reported with Albenza (albendazole) in a patient who took at least 16 grams over 12 hours. No untoward effects were reported. In case of overdosage, symptomatic therapy (e.g., gastric lavage and activated charcoal) and general supportive measures are recommended.

DOSAGE AND ADMINISTRATION

Dosing of Albenza will vary, depending upon which of the following parasitic infections is being treated.

Patients being treated for neurocysticercosis should receive appropriate steroid and anticonvulsant therapy as required. Oral or intravenous corticosteroids should be considered to prevent cerebral hypertensive episodes during the first week of treatment.

HOW SUPPLIED

Albenza (albendazole) is supplied as 200 mg, white to off-white, circular, biconvex, bevel-edged, film-coated Tiltab® tablets in bottles of 112.

NDC 0007-5500-40........................................ Bottles of 112

Store between 20° and 25°C (68° and 77°F).

Glaxosmithkline, Research Triangle Park, NC 27709

©2001, Glaxosmithkline. All rights reserved.

September 2001/AL:L3

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