Letrozole: uses, appearance and warnings

Letrozole tablets are an aromatase inhibitor indicated for: Adjuvant treatment of postmenopausal women with hormone receptor positive early breast cancer. ( 1.1 ) Extended adjuvant treatment of postmenopausal women with early breast cancer who have received prior standard adjuvant tamoxifen therapy. ( 1.2 ) First and second-line treatment of postmenopausal women with hormone receptor positive or unknown advanced breast cancer. ( 1.3 ) 1.1 Adjuvant Treatment of Early Breast Cancer Letrozole tablets are indicated for the adjuvant treatment of postmenopausal women with hormone receptor positive early breast cancer. 1.2 Extended Adjuvant Treatment of Early Breast Cancer Letrozole tablets are indicated for the extended adjuvant treatment of early breast cancer in postmenopausal women, who have received 5 years of adjuvant tamoxifen therapy. The effectiveness of letrozole tablets in extended adjuvant treatment of early breast cancer is based on an analysis of disease-free survival (DFS) in patients treated with letrozole tablets for a median of 60 months [see Clinical Studies (14.2 , 14.3) ] . 1.3 First and Second-Line Treatment of Advanced Breast Cancer Letrozole tablets are indicated for first-line treatment of postmenopausal women with hormone receptor positive or unknown, locally advanced or metastatic breast cancer. Letrozole tablets are also indicated for the treatment of advanced breast cancer in postmenopausal women with disease progression following antiestrogen therapy [see Clinical Studies (14.4 , 14.5) ].

2.5 mg tablets: Yellow colored, film-coated, round shaped tablets debossed with one side 'N' and other side 'L'. 2.5 mg tablets. ( 3 )

Packaged in HDPE bottles with a child resistant closure (30 tablets & 90 tablets) and continuous thread closure (1000 tablets). 2.5 milligram tablets Bottles of 30 tablets NDC 51991-759-33 Bottle of 90 tablets NDC 51991-759-90 Bottles of 1000 tablets NDC 51991-759-10 Store at 25°C (77°F); excursions permitted to 15°C to 30°C (59°F to 86°F) [see USP Controlled Room Temperature].

Pregnancy: Letrozole can cause fetal harm [see Use in Specific Populations (8.1) ] . Known hypersensitivity to the active substance, or to any of the excipients [see Adverse Reactions (6) ] . Pregnancy. ( 4 ) Known hypersensitivity to the active substance, or to any of the excipients. ( 4 )

Decreases in bone mineral density may occur. Consider bone mineral density monitoring. ( 5.1 ) Increases in total cholesterol may occur. Consider cholesterol monitoring. ( 5.2 ) Fatigue, dizziness, and somnolence may occur. Exercise caution when operating machinery. ( 5.4 ) Embryo-Fetal Toxicity: Can cause fetal harm when administered to pregnant women. Obtain a pregnancy test in females of reproductive potential. Advise females of reproductive potential to use effective contraception. ( 5.6 , 8.1 , 8.3 ) 5.1 Bone Effects Use of letrozole tablets may cause decreases in bone mineral density (BMD). Consideration should be given to monitoring BMD. Results of a safety study to evaluate safety in the adjuvant setting comparing the effect on lumbar spine (L2-L4) BMD of adjuvant treatment with letrozole to that with tamoxifen showed at 24 months a median decrease in lumbar spine BMD of 4.1% in the letrozole arm compared to a median increase of 0.3% in the tamoxifen arm (difference = 4.4%) ( P <0.0001) [see Adverse Reactions (6) ] . Updated results from the BMD substudy (MA-17B) in the extended adjuvant setting demonstrated that at 2 years patients receiving letrozole had a median decrease from baseline of 3.8% in hip BMD compared to a median decrease of 2.0% in the placebo group. The changes from baseline in lumbar spine BMD in letrozole and placebo treated groups were not significantly different [see Adverse Reactions (6) ]. In the adjuvant trial (BIG 1-98) the incidence of bone fractures at any time after randomization was 14.7% for letrozole and 11.4% for tamoxifen at a median follow-up of 96 months. The incidence of osteoporosis was 5.1% for letrozole and 2.7% for tamoxifen [see Adverse Reactions (6) ] . In the extended adjuvant trial (MA-17), the incidence of bone fractures at any time after randomization was 13.3% for letrozole and 7.8% for placebo at a median follow-up of 62 months. The incidence of new osteoporosis was 14.5% for letrozole and 7.8% for placebo [see Adverse Reactions (6) ] . 5.2 Cholesterol Consideration should be given to monitoring serum cholesterol. In the adjuvant trial (BIG 1-98), hypercholesterolemia was reported in 52.3% of letrozole patients and 28.6% of tamoxifen patients. Grade 3-4 hypercholesterolemia was reported in 0.4% of letrozole patients and 0.1% of tamoxifen patients. Also in the adjuvant setting, an increase of greater than or equal to 1.5 × upper limit of normal (ULN) in total cholesterol (generally nonfasting) was observed in patients on monotherapy who had baseline total serum cholesterol within the normal range (i.e., less than =1.5 × ULN) in 155/1843 (8.4%) patients on letrozole vs 71/1840 (3.9%) patients on tamoxifen. Lipid lowering medications were required for 29% of patients on letrozole and 20% on tamoxifen [see Adverse Reactions (6) ] . 5.3 Hepatic Impairment Subjects with cirrhosis and severe hepatic impairment who were dosed with 2.5 mg of letrozole tablets experienced approximately twice the exposure to letrozole tablets as healthy volunteers with normal liver function [see Clinical Pharmacology (12.3) ]. Therefore, a dose reduction is recommended for this patient population. The effect of hepatic impairment on letrozole tablets exposure in cancer patients with elevated bilirubin levels has not been determined [see Dosage and Administration (2.5) ]. 5.4 Fatigue and Dizziness Because fatigue, dizziness, and somnolence have been reported with the use of letrozole tablets, caution is advised when driving or using machinery until it is known how the patient reacts to letrozole tablets use. 5.5 Laboratory Test Abnormalities No dose-related effect of letrozole tablets on any hematologic or clinical chemistry parameter was evident. Moderate decreases in lymphocyte counts, of uncertain clinical significance, were observed in some patients receiving letrozole tablets 2.5 mg. This depression was transient in about half of those affected. Two patients on letrozole tablets developed thrombocytopenia; relationship to the study drug was unclear. Patient withdrawal due to laboratory abnormalities, whether related to study treatment or not was infrequent. 5.6 Embryo-Fetal Toxicity Based on post-marketing reports, findings from animal studies and the mechanism of action, letrozole tablets can cause fetal harm and is contraindicated for use in pregnant women. In post-marketing reports, use of letrozole during pregnancy resulted in cases of spontaneous abortions and congenital birth defects. Letrozole caused embryo-fetal toxicities in rats and rabbits at maternal exposures that were below the maximum recommended human dose (MHRD) on a mg/m 2 basis. Advise pregnant women of the potential risk to a fetus. Advise females of reproductive potential to use effective contraception during therapy with letrozole tablets and for at least 3 weeks after the last dose [see Adverse Reactions (6.2) , Use in Specific Populations (8.1 , 8.3) , and Clinical Pharmacology (12.1) ] .

The following adverse reactions are discussed in greater detail in other sections of the labeling. Bone effects [see Warnings and Precautions (5.1) ] Increases in cholesterol [see Warnings and Precautions (5.2) ] Fatigue and Dizziness [see Warnings and Precautions (5.4) ] The most common adverse reactions (greater than 20%) were hot flashes, arthralgia; flushing, asthenia, edema, arthralgia, headache, dizziness, hypercholesterolemia, sweating increased, bone pain; and musculoskeletal. ( 6 ) To report SUSPECTED ADVERSE REACTIONS, contact Breckenridge Pharmaceutical, Inc., at 1-800-367-3395 or FDA at 1-800-FDA-1088 or www.fda.gov/medwatch . …

Tamoxifen Coadministration of letrozole tablets and tamoxifen 20 mg daily resulted in a reduction of letrozole plasma levels of 38% on average (Study P015). Clinical experience in the second-line breast cancer trials (AR/BC2 and AR/BC3) indicates that the therapeutic effect of letrozole tablets therapy is not impaired if letrozole tablets are administered immediately after tamoxifen. Cimetidine A pharmacokinetic interaction study with cimetidine (Study P004) showed no clinically significant effect on letrozole pharmacokinetics. Warfarin An interaction study (P017) with warfarin showed no clinically significant effect of letrozole on warfarin pharmacokinetics. Other Anticancer Agents There is no clinical experience to date on the use of letrozole tablets in combination with other anticancer agents.