Cases of peripheral neuropathy have been reported in patients treated with ZAVESCA®. All patients undergoing ZAVESCA® treatment should undergo baseline and repeat neurological evaluations at approximately 6-month intervals. Patients who develop symptoms such as numbness and tingling should have a careful reassessment of the risk/benefit of ZAVESCA® therapy and cessation of treatment may be considered.
Therapy should be directed by physicians knowledgeable in the management of patients with Gaucher disease.
Approximately 30% of patients have reported tremor or exacerbation of existing tremor on treatment. These tremors were described as an exaggerated physiological tremor of the hands. Tremor usually began within the first month of therapy and in many cases resolved between 1 to 3 months during treatment. Dose reduction may ameliorate the tremor usually within days but discontinuation with treatment may sometimes be required.
Diarrhea and Weight Loss
Diarrhea and weight loss were common in clinical studies of patients treated with ZAVESCA®, approximately 85% and up to 65% of treated patients, respectively, reporting these conditions. Diarrhea appears to be the result of the disaccharidase inhibitory activity of ZAVESCA®, with a resultant osmotic diarrhea. It is unclear if weight loss results from the diarrhea and associated gastrointestinal complaints, a decrease in food intake, or a combination of these or other factors. The incidence of diarrhea was noted to decrease over time with continued ZAVESCA® treatment, and was noted to result in an increase in the use of anti-diarrheal medications, most commonly loperamide. Patients may be instructed to avoid high carbohydrate content foods during treatment with ZAVESCA® if they present with diarrhea. The incidence of weight loss was most evident in the first 12 months of treatment.
Male patients should maintain reliable contraceptive methods while taking ZAVESCA®. Studies in the rat have shown that miglustat adversely affects spermatogenesis and sperm parameters, thereby reducing fertility. Until further information is available, it is advised that before seeking to conceive, male patients should cease ZAVESCA® and maintain reliable contraceptive methods for 3 months thereafter (see Carcinogenesis, Mutagenesis, and Impairment of Fertility).
INFORMATION FOR PATIENTS
Patients should be informed of the potential risks and benefits of ZAVESCA® and of alternative modes of therapy. Patients should be advised that diarrhea, gastrointestinal complaints, and weight loss are common side effects of ZAVESCA® therapy, and to adhere to dietary instructions. Patients should also be advised to promptly report any numbness, pain, or burning in the hands and feet, and the development of tremor or worsening in an existing tremor.
While co-administration of ZAVESCA® appeared to increase the clearance of Cerezyme by 70%, these results are not conclusive because of the small number of subjects studied and because patients took variable doses of Cerezyme. Combination therapy with Cerezyme (imiglucerase) and ZAVESCA® is not indicated (see CLINICAL PHARMACOLOGY, Drug Interactions).
Histopathology findings in the absence of clinical signs in the central nervous system of the monkey (brain, spine) that included vascular mineralization, in addition to mineralization and necrosis of white matter were observed at >750 mg/kg/day (4 times the human therapeutic systemic exposure based on area-under-the-plasma-concentration curve [AUC] comparisons) in a 52-week oral toxicity study using doses of 750 and 2000 mg/kg/d. Vacuolization of white matter was observed in rats dosed orally by gavage at >/= 180 mg/kg/d (6 times the human therapeutic exposure based on surface area comparisons, mg/m2) in a 4-week study using doses of 180, 840, and 4200 mg/kg/d. Vacuolization can sometimes occur as an artifact of tissue processing. Findings in dogs included tremor and absent corneal reflexes at 105 mg/kg/day (10 times the human therapeutic systemic exposure, based on body surface area comparisons mg/m2) after a 4-week oral gavage toxicity study using doses of 35, 70, 105, and 140 mg/kg/d. Ataxia, diminished/absent pupillary, palpebral, or patellar reflexes were observed in a dog at >/=495 mg/kg/day (50 times the human therapeutic systemic exposure based on body surface area comparisons, mg/m2), in a 2-week oral gavage toxicity study using doses of 85, 165, 495, and 825 mg/kg/d.
Cataracts were observed in rats at >/= 180 mg/kg/day (4 times the human therapeutic systemic exposure, based on AUC) in a 52-week oral gavage toxicity study using doses of 180, 420, 840, and 1680 mg/kg/d.
Gastrointestinal necrosis, inflammation, and hemorrhage were observed in dogs at >/= 85 mg/kg/day (9 times the human therapeutic systemic exposure based on body surface area comparisons, mg/m2) after a 2-week oral (capsule) toxicity study using doses of 85, 165, 495, and 825 mg/kg/d. Similar GI toxicity occurred in rats at 1200 mg/kg/day (7 times the human therapeutic systemic exposure, based on AUC) in a 26-week oral gavage toxicity study using doses of 300, 600, and 1200 mg/kg/d. In monkeys, similar GI toxicity occurred at >/=750 mg/kg/day (6x times the human therapeutic systemic exposure based on AUC) following a 52-week oral gavage toxicity study using doses of 750 and 2000 mg/kg/d.
CARCINOGENESIS, MUTAGENESIS, AND IMPAIRMENT OF FERTILITY
Long-term studies in animals to evaluate the carcinogenic potential of miglustat have not been conducted. Miglustat was not mutagenic or clastogenic in a battery of in vitro and in vivo assays including the bacterial reverse mutation (Ames), chromosomal aberration (in human lymphocytes), gene mutation in mammalian cells (Chinese hamster ovary), and mouse micronucleus assays.
Male rats, given 20 mg/kg/day miglustat by (systemic exposure less than the human therapeutic systemic exposure based on body surface area comparisons, mg/m2) oral gavage 14 days prior to mating, had decreased spermatogenesis with altered sperm morphology and motility and decreased fertility. Decreased spermatogenesis was reversible following 6 weeks of drug withdrawal. A higher doses of 60 mg/kg/day (2 times the human therapeutic systemic exposure based on body surface area comparison, mg/m2) resulted in seminiferous tubule and testicular atrophy/degeneration.
Female rats were given oral gavage doses of 20, 60, 180 mg/kg/day beginning 14 days before mating and continuing through gestation. Effects observed at 20 mg/kg/day (systemic exposure less than the human therapeutic systemic exposure, based on body surface area comparisons) included decreased corpora lutea, increased postimplantation loss, and decreased live births.
Pregnancy Category X. See CONTRAINDICATIONS section.
There are no adequate and well-controlled studies of miglustat in pregnant women. ZAVESCA® should not be used during pregnancy.
LABOR AND DELIVERY
Studies in pregnant rats exposed to ZAVESCA® during gestation through lactation are associated with dystocia and delayed parturition at systemic exposure 2 times the human therapeutic systemic exposure, based on body surface area comparisons.
It is not known whether miglustat is 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 miglustat, ZAVESCA® should not be used in nursing mothers unless the potential benefit justifies the potential risk to the infant. A decision should be made whether to discontinue nursing or discontinue the drug, taking into account the importance of the drug to the lactating woman.
The safety and effectiveness of ZAVESCA® have not been evaluated in patients under the age of 18. Treatment with ZAVESCA® is associated with diarrhea and weight loss in approximately 85% and up to 65%, respectively, of adult patients. The effects of ZAVESCA® on growth and development in children have not been evaluated.
Clinical studies of ZAVESCA® did not include sufficient numbers of patients aged 65 and over to determine whether they respond differently than younger patients. Other reported clinical experience has not identified differences in responses between 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, and cardiac function and of concomitant disease or other drug therapy.
Miglustat is known to be substantially excreted by the kidney, and the risk of adverse reactions to this drug may be greater in patients with impaired renal function. The clearance of miglustat is decreased by 40 to 60% in patients with mild to moderate renal impairment, and up to 70% in patients with severe renal impairment. As a result of this, dose reductions are recommended for those patients with mild to moderate renal impairment, the reduction being dependent upon the level of their creatinine clearance adjustment. For those patients with severe renal impairment, treatment with miglustat is not recommended. Since 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.