WARNINGS
Hypercalcemia and Tumor Flare: As with other antiestrogens, hypercalcemia and tumor flare have been reported in some breast cancer patients with bone metastases during the first weeks of treatment with FARESTON. Tumor flare is a syndrome of diffuse musculoskeletal pain and erythema with increased size of tumor lesions that later regress. It is often accompanied by hypercalcemia. Tumor flare does not imply failure of treatment or represent tumor progression. If hypercalcemia occurs, appropriate measures should be instituted and if hypercalcemia is severe, FARESTON treatment should be discontinued.
Tumorigenicity: Since most toremifene trials have been conducted in patients with metastatic disease, adequate data on the potential endometrial tumorigenicity of long-term treatment with FARESTON are not available. Endometrial hyperplasia has been reported. Some patients treated with FARESTON have developed endometrial cancer, but circumstances (short duration of treatment or prior antiestrogen treatment or premalignant conditions) make it difficult to establish the role of FARESTON.
Endometrial hyperplasia of the uterus was observed in monkeys following 52 weeks of treatment at ≥1 mg/kg and in dogs following 16 weeks of treatment at ≥3 mg/kg with toremifene (about 1/4 and 1.4 times, respectively, the daily maximum recommended human dose on a mg/m2 basis).
Pregnancy: FARESTON may cause fetal harm when administered to pregnant women. Studies in rats at doses ≥1.0 mg/kg/day (about 1/4 the daily maximum recommended human dose on a mg/m2 basis) administered during the period of organogenesis, have shown that toremifene is embryotoxic and fetotoxic, as indicated by intrauterine mortality, increased resorption, reduced fetal weight, and fetal anomalies; including malformation of limbs, incomplete ossification, misshapen bones, ribs/spine anomalies, hydroureter, hydronephrosis, testicular displacement, and subcutaneous edema. Fetal anomalies may have been a consequence of maternal toxicity. Toremifene has been shown to cross the placenta and accumulate in the rodent fetus.
In rodent models of fetal reproductive tract development, toremifene produced inhibition of uterine development in female pups similar to diethylstilbestrol (DES) and tamoxifen. The clinical relevance of these changes is not known.
Embryotoxicity and fetotoxicity were observed in rabbits at doses ≥1.25 mg/kg/day and 2.5 mg/kg/day, respectively (about 1/3 and 2/3 the daily maximum recommended human dose on a mg/m2 basis); fetal anomalies included incomplete ossification and anencephaly.
There are no studies in pregnant women. If FARESTON is used during pregnancy, or if the patient becomes pregnant while receiving this drug, the patient should be apprised of the potential hazard to the fetus or potential risk for loss of the pregnancy.
PRECAUTIONS
General: Patients with a history of thromboembolic diseases should generally not be treated with FARESTON. In general, patients with preexisting endometrial hyperplasia should not be given long-term FARESTON treatment. Patients with bone metastases should be monitored closely for hypercalcemia during the first weeks of treatment (see WARNINGS). Leukopenia and thrombocytopenia have been reported rarely; leukocyte and platelet counts should be monitored when using FARESTON in patients with leukopenia and thrombocytopenia.
Information for Patients: Vaginal bleeding has been reported in patients using FARESTON. Patients should be informed about this and instructed to contact their physician if such bleeding occurs.
Patients with bone metastases should be informed about the typical signs and symptoms of hypercalcemia and instructed to contact their physician for further assessment if such signs or symptoms occur.
Laboratory Tests: Periodic complete blood counts, calcium levels, and liver function tests should be obtained.
Drug-drug Interactions: Drugs that decrease renal calcium excretion, eg, thiazide diuretics, may increase the risk of hypercalcemia in patients receiving FARESTON. There is a known interaction between antiestrogenic compounds of the triphenylethylene derivative class and coumarin-type anticoagulants (eg, warfarin), leading to an increased prothrombin time. When concomitant use of anticoagulants with FARESTON is necessary, careful monitoring of the prothrombin time is recommended.
Cytochrome P450 3A4 enzyme inducers, such as phenobarbital, phenytoin, and carbamazepine increase the rate of toremifene metabolism, lowering the steady-state concentration in serum. Metabolism of toremifene may be inhibited by drugs known to inhibit the CYP3A4-6 enzymes. Examples of such drugs are ketoconazole and similar antimycotics as well as erythromycin and similar macrolides. This interaction has not been studied and its clinical relevance is uncertain.
Carcinogenesis, Mutagenesis, and Impairment of Fertility: Conventional carcinogenesis studies in rats at doses of 0.12 to 12 mg/kg/day (about 1/100 to 1.5 times the daily maximum recommended human dose on a mg/m2 basis) for up to 2 years did not show evidence of carcinogenicity. Studies in mice at doses of 1.0 to 30.0 mg/kg/day (about 1/15 to 2 times the daily maximum recommended human dose on a mg/m2 basis) for up to 2 years revealed increased incidence of ovarian and testicular tumors, and increased incidence of osteoma and osteosarcoma. The significance of the mouse findings is uncertain because of the different role of estrogens in mice and the estrogenic effect of toremifene in mice. An increased incidence of ovarian and testicular tumors in mice has also been observed with other human antiestrogenic agents that have primarily estrogenic activity in mice.
Toremifene has not been shown to be mutagenic in in vitro tests (Ames and E. coli bacterial tests). Toremifene is clastogenic in vitro (chromosomal aberrations and micronuclei formation in human lymphoblastoid MCL-5 cells) and in vivo (chromosomal aberrations in rat hepatocytes). No significant adduct formation could be detected using 32P post-labeling in liver DNA from rats administered toremifene when compared to tamoxifen at similar doses. A study in cultured human lymphocytes indicated that adducting activity of toremifene, detected by 32P post-labeling, was about 1/6 that of tamoxifen at approximately equipotent concentrations. In addition, the DNA adducting activity of toremifene in salmon sperm, using 32P post-labeling, was 1/6 and 1/4 that observed with tamoxifen at equivalent concentrations following activation by rat and human microsomal systems, respectively. However, toremifene exposure is fourfold the exposure of tamoxifen based on human AUC in serum at recommended clinical doses.
Toremifene produced impairment of fertility and conception in male and female rats at doses ≥25.0 and 0.14 mg/kg/day, respectively (about 3.5 times and 1/50 the daily maximum recommended human dose on a mg/m2 basis). At these doses, sperm counts, fertility index, and conception rate were reduced in males with atrophy of seminal vesicles and prostate. In females, fertility and reproductive indices were markedly reduced with increased pre- and post-implantation loss. In addition, offspring of treated rats exhibited depressed reproductive indices. Toremifene produced ovarian atrophy in dogs administered doses ≥3 mg/kg/day (about 1.5 times the daily maximum recommended human dose on a mg/m2 basis) for 16 weeks. Cystic ovaries and reduction in endometrial stromal cellularity were observed in monkeys at doses ≥1 mg/kg/day (about 1/4 the daily maximum recommended human dose on a mg/m2 basis) for 52 weeks.
Pregnancy: Pregnancy Category D: (see WARNINGS).
Nursing mothers: Toremifene has been shown to be excreted in the milk of lactating rats. It is not known if this drug is excreted in human milk. (See WARNINGS and PRECAUTIONS).
Pediatric use: There is no indication for use of FARESTON in pediatric patients.
Geriatric use: The median ages in the three controlled studies ranged from 60 to 66 years. No significant age-related differences in FARESTON effectiveness or safety were noted.
Race: Fourteen percent of patients in the North American Study were non-Caucasian. No significant race-related differences in FARESTON effectiveness or safety were noted.
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