Leton

Treatment Of Paget’s Disease Of Bone

Leton injection is indicated for the treatment of symptomatic Paget's disease of bone in patients with moderate to severe disease characterized by polyostotic involvement with elevated serum alkaline phosphatase and urinary hydroxyproline excretion. There is no evidence that the prophylactic use of calcitonin-salmon is beneficial in asymptomatic patients. Leton injection should be used only in patients who do not respond to alternative treatments or for whom such treatments are not suitable (e.g., patients for whom other therapies are contraindicated or for patients who are intolerant or unwilling to use other therapies).

Treatment Of Hypercalcemia

Leton injection is indicated for the early treatment of hypercalcemic emergencies, along with other appropriate agents, when a rapid decrease in serum calcium is required, until more specific treatment of the underlying disease can be accomplished. It may also be added to existing therapeutic regimens for hypercalcemia such as intravenous fluids and furosemide, oral phosphate or corticosteroids, or other agents.

Treatment Of Postmenopausal Osteoporosis

Leton injection is indicated for the treatment of postmenopausal osteoporosis in women greater than 5 years postmenopause. The evidence of efficacy for calcitonin-salmon injection is based on increases in total body calcium observed in clinical trials. Fracture reduction efficacy has not been demonstrated. Leton injection should be reserved for patients for whom alternative treatments are not suitable (e.g., patients for whom other therapies are contraindicated or for patients who are intolerant or unwilling to use other therapies).

Important Limitations Of Use

Due to the possible association between malignancy and calcitonin-salmon use, the need for continued therapy should be re-evaluated on a periodic basis.

Paget’s Disease Of Bone

The recommended dose of Leton injection for treatment of symptomatic Paget's disease of bone is 100 International Units (0.5 mL) per day administered subcutaneously or intramuscularly.

Hypercalcemia

The recommended starting dose of Leton injection for early treatment of hypercalcemia is 4 International Units/kg body weight every 12 hours by subcutaneous or intramuscular injection. If the response to this dose is not satisfactory after one or two days, the dose may be increased to 8 International Units/kg every 12 hours. If the response remains unsatisfactory after two more days, the dose may be further increased to a maximum of 8 International Units/kg every 6 hours.

Postmenopausal Osteoporosis

The recommended dose of Leton injection for treatment of postmenopausal osteoporosis in women greater than 5 years postmenopause is 100 International Units (0.5 mL) per day administered subcutaneously or intramuscularly. The minimum effective dose of Leton injection for the prevention of vertebral bone mineral density loss has not been established.

Preparation And Administration

Visually inspect Leton vials. Leton injection is a clear, colorless, solution. If the solution is not clear and colorless, or contains any particles, or if the vial is damaged, do not administer the solution.

If the volume of Leton injection to be injected exceeds 2 mL, intramuscular injection is preferable and the total dose should be distributed across multiple sites of injection.

Instruct patients to use sterile injection technique when administering Leton injection, and to dispose of needles properly.

Recommendations For Calcium And Vitamin D Supplementation

Patients who use Leton injection for treatment of postmenopausal osteoporosis should receive adequate calcium (at least 1000 mg elemental calcium per day) and vitamin D (at least 400 International Units per day).

Hypersensitivity to calcitonin-salmon or any of the excipients. Reactions have included anaphylaxis with death, bronchospasm, and swelling of the tongue or throat.

WARNINGS

Included as part of the PRECAUTIONS section.

PRECAUTIONS

Hypersensitivity Reactions

Serious hypersensitivity reactions have been reported in patients receiving Leton injection, e.g., bronchospasm, swelling of the tongue or throat, anaphylactic shock, and death due to anaphylaxis. Appropriate medical support and monitoring measures should be readily available when Leton injection is administered. If anaphylaxis or other severe hypersensitivity/allergic reactions occur, initiate appropriate treatment.

For patients with suspected hypersensitivity to calcitonin-salmon, skin testing should be considered prior to treatment utilizing a dilute, sterile solution of Leton injection. Healthcare providers may wish to refer patients who require skin testing to an allergist. A detailed skin testing protocol is available from the Medical Services Department of Novartis Pharmaceuticals Corporation.

Hypocalcemia

Hypocalcemia associated with tetany (i.e., muscle cramps, twitching) and seizure activity has been reported with Leton injection therapy. Hypocalcemia must be corrected before initiating therapy. Other disorders affecting mineral metabolism (such as vitamin D deficiency) should also be effectively treated. In patients at risk for hypocalcemia, provisions for parenteral calcium administration should be available during the first several administrations of calcitoninsalmon and serum calcium and symptoms of hypocalcemia should be monitored. Use of Leton injection for the treatment of Paget's disease or postmenopausal osteoporosis is recommended in conjunction with an adequate intake of calcium and vitamin D.

Malignancy

In a meta-analysis of 21 randomized, controlled clinical trials with calcitonin-salmon (nasal spray or investigational oral formulations), the overall incidence of malignancies reported was higher among calcitonin-salmon-treated patients (4.1%) compared with placebo-treated patients (2.9%). This suggests an increased risk of malignancies in calcitonin-salmontreated patients compared to placebo-treated patients. It is not possible to exclude an increased risk when calcitoninsalmon is administered long-term subcutaneously, intramuscularly, or intravenously. The benefits for the individual patient should be carefully considered against possible risks.

Antibody Formation

Circulating antibodies to calcitonin-salmon have been reported with Leton injection. The possibility of antibody formation should be considered in any patient with an initial response to Leton injection who later stops responding to treatment.

Urine Sediment Abnormalities

Coarse granular casts and casts containing renal tubular epithelial cells were reported in young adult volunteers at bed rest who were given injectable calcitonin-salmon to study the effect of immobilization on osteoporosis. There was no other evidence of renal abnormality and the urine sediment normalized after calcitonin-salmon was stopped. Periodic examinations of urine sediment should be considered.

Nonclinical Toxicology

Carcinogenesis, Mutagenesis, Impairment Of Fertility

Carcinogenicity

The incidence of pituitary adenomas was increased in rats after one and two years of subcutaneous exposure to synthetic calcitonin-salmon. The significance of this finding to humans is unknown because pituitary adenomas are very common in rats as they age, the pituitary adenomas did not transform into metastatic tumors, there were no other clear treatment-related neoplasms, and synthetic calcitonin-salmon related neoplasms were not observed in mice after two years of dosing.

Rat findings

The only clear neoplastic finding in rats dosed subcutaneously with calcitonin-salmon was an increase in the incidence of pituitary adenomas in male Fisher 344 rats and female Sprague Dawley rats after one year of dosing and male Sprague Dawley rats dosed for one and two years. In female Sprague Dawley rats, the incidence of pituitary adenomas after two years was high in all treatment groups (between 80% and 92% including the control groups) such that a treatment-related effect could not be distinguished from natural background incidence. The lowest dose in male Sprague Dawley rats that developed an increased incidence of pituitary adenomas after two years of dosing (1.7 International Units/kg/day) is approximately 1/6^thof the maximum recommended subcutaneous dose in humans (100 International Units/day) based on body surface area conversion between rats and humans. The findings suggest that calcitonin-salmon reduced the latency period for development of non-functioning pituitary adenomas.

Mouse findings

No carcinogenicity potential was evident in male or female mice dosed subcutaneously for two years with synthetic calcitonin-salmon at doses up to 800 International Units/kg/day. The 800 International Units/kg/day dose is approximately 39 times the maximum recommended subcutaneous dose in humans (100 International Units/day) based on body surface area conversion between mice and humans.

Mutagenesis

Synthetic calcitonin-salmon tested negative for mutagenicity using Salmonella typhimurium (5 strains) and Escherichia coli (2 strains), with and without rat liver metabolic activation, and was not clastogenic in a chromosome aberration test in Chinese Hamster V79 cells. There was no evidence that calcitonin-salmon was clastogenic in the in vivo mouse micronucleus test.

Fertility

Effects of calcitonin-salmon on fertility have not been assessed in animals.

Use In Specific Populations

Pregnancy

Pregnancy Category C

Risk Summary

There are no adequate and well-controlled studies in pregnant women. Leton injection should be used during pregnancy only if the potential benefit justifies the use as compared with potential risks to the patient and fetus. Based on animal data, Leton is predicted to have low probability of increasing the risk of adverse developmental outcomes above background risk.

Animal Data

Calcitonin-salmon has been shown to cause a decrease in fetal birth weights in rabbits when given by subcutaneous injection in doses 4-18 times the parenteral dose recommended for human use (of 54 International Units/m²).

No embryo/fetal toxicities related to Leton were reported from maternal subcutaneous daily doses in rats up to 80 International Units /kg/day from gestation day 6 to 15.

Nursing Mothers

It is not known whether this drug is excreted in human milk. No studies have been conducted to assess the impact of Leton on milk production in humans, its presence in human breast milk, or its effects on the breastfed child. Because many drugs are excreted in human milk, caution should be exercised when Leton is administered to a nursing woman. Calcitonin has been shown to inhibit lactation in rats.

Pediatric Use

Safety and effectiveness in pediatric patients have not been established.

Geriatric Use

Clinical studies of Leton injection did not include sufficient numbers of subjects aged 65 years and older to determine whether they respond differently from younger subjects. Other reported clinical experience has not identified differences in responses between the 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, or cardiac function, and of concomitant disease or other drug therapy.

The following serious adverse reactions are discussed in greater detail in other sections of the label:

• Hypersensitivity Reactions, including anaphylaxis
• Hypocalcemia
• Malignancy

Clinical Trials Experience

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.

The safety of calcitonin-salmon injection was assessed in open-label trials several months to two years in duration. The most common adverse reactions are discussed below.

Nausea

Nausea with or without vomiting has been noted in about 10% of patients treated with calcitonin-salmon. It is most evident when treatment is first initiated and tends to decrease or disappear with continued administration.

Dermatologic Reactions

Local inflammatory reactions at the site of subcutaneous or intramuscular injection have been reported in about 10% of patients. Flushing of face or hands occurred in about 2%–5% of patients. Skin rashes and pruritus of the ear lobes have also been reported.

Other Adverse Reactions

Nocturia, feverish sensation, pain in the eyes, poor appetite, abdominal pain, pedal edema, and salty taste have been reported in patients treated with calcitonin-salmon injection.

Malignancy

A meta-analysis of 21 randomized, controlled clinical trials with calcitonin-salmon (nasal spray or investigational oral formulations) was conducted to assess the risk of malignancies in calcitonin-salmon-treated patients compared to placebo-treated patients. The trials in the meta-analysis ranged in duration from 6 months to 5 years and included a total of 10883 patients (6151 treated with calcitonin-salmon and 4732 treated with placebo). The overall incidence of malignancies reported in these 21 trials was higher among calcitonin-salmon-treated patients (254/6151 or 4.1%) compared with placebo-treated patients (137/4732 or 2.9%). Findings were similar when analyses were restricted to the 18 nasal spray only trials [calcitonin-salmon 122/2712 (4.5%); placebo 30/1309 (2.3%)].

The meta-analysis results suggest an increased risk of overall malignancies in calcitonin-salmon-treated patients compared to placebo-treated patients when all 21 trials are included and when the analysis is restricted to the 18 nasal spray only trials (see Table 1). It is not possible to exclude an increased risk when calcitonin-salmon is administered by the subcutaneous, intramuscular, or intravenous route because these routes of administration were not investigated in the meta-analysis. The increased malignancy risk seen with the meta-analysis was heavily influenced by a single large 5-year trial, which had an observed risk difference of 3.4% [95% CI (0.4%, 6.5%)]. Imbalances in risks were still observed when analyses excluded basal cell carcinoma (see Table 1); the data were not sufficient for further analyses by type of malignancy. A mechanism for these observations has not been identified. Although a definitive causal relationship between calcitonin-salmon use and malignancies cannot be established from this meta-analysis, the benefits for the individual patient should be carefully evaluated against all possible risks.

Table 1: Risk Difference for Malignancies in Calcitonin-Salmon-Treated Patients Compared with Placebo-Treated Patients

Postmarketing Experience

Because postmarketing adverse reactions are reported voluntarily from a population of uncertain size, it is not always possible to reliably estimate their frequency or establish a causal relationship to drug exposure.

The following adverse reactions have been reported during post-approval use of Leton injection.

Allergic / Hypersensitivity Reactions: Serious hypersensitivity reactions have been reported in patients receiving calcitonin-salmon injection, e.g., bronchospasm, swelling of the tongue or throat, anaphylactic shock, and death due to anaphylaxis.

Skin and subcutaneous tissue disorders: Urticaria

Hypocalcemia: Hypocalcemia with tetany (i.e. muscle cramps, twitching) and seizure activity have been reported.

Body as a Whole: influenza-like symptoms, fatigue, edema (facial, peripheral, and generalized)

Musculoskeletal: arthralgia, musculoskeletal pain

Cardiovascular: hypertension

Gastrointestinal: abdominal pain, diarrhea

Urinary System: polyuria

Nervous System: dizziness, headache, paresthesia, tremor

Vision: visual disturbance

Immunogenicity

Consistent with the potentially immunogenic properties of medicinal products containing peptides, administration of Leton may trigger the development of anti-calcitonin antibodies. Circulating antibodies to calcitonin-salmon after 218 months of treatment have been reported in about one-half of the patients with Paget's disease in whom antibody studies were done. In some cases, high antibody titers are found; these patients usually will have a loss of response to treatment.

The incidence of antibody formation is highly dependent on the sensitivity and specificity of the assay. Additionally, the observed incidence of a positive antibody test result may be influenced by several factors, including assay methodology, sample handling, timing of sample collection, concomitant medications, and underlying disease. For these reasons, comparison of antibodies among different calcitonin-salmon products may be misleading.

The pharmacologic actions of Leton injection suggest that hypocalcemic tetany could occur in overdose. Therefore, provisions for parenteral administration of calcium should be available for the treatment of overdose.

A dose of calcitonin-salmon l000 International Units subcutaneously may produce nausea and vomiting. Doses of 32 International Units per kg per day for 1–2 days demonstrate no other adverse effects. Data on chronic high-dose administration are insufficient to assess toxicity.

Bone

Single injections of calcitonin-salmon caused a marked transient inhibition of the ongoing bone resorptive process. With prolonged use, there is a persistent, smaller decrease in the rate of bone resorption. Histologically, this is associated with a decreased number of osteoclasts and an apparent decrease in their resorptive activity.

In healthy adults, who have a relatively low rate of bone resorption, the administration of exogenous calcitonin-salmon results in decreases in serum calcium within the limits of the normal range. In healthy children and in patients whose bone resorption is more rapid, decreases in serum calcium are more pronounced in response to calcitonin-salmon.

Kidney

Studies with injectable calcitonin-salmon show increases in the excretion of filtered phosphate, calcium, and sodium by decreasing their tubular reabsorption.

Gastrointestinal Tract

Some evidence from studies with injectable preparations suggests that calcitonin-salmon may have effects on the gastrointestinal tract. Short-term administration of injectable calcitonin-salmon results in marked transient decreases in the volume and acidity of gastric juice and in the volume and the trypsin and amylase content of pancreatic juice. Whether these effects continue to be elicited after each injection of calcitonin-salmon during chronic therapy has not been investigated.

The absolute bioavailability of calcitonin-salmon is approximately 66% and 71% after intramuscular or subcutaneous injection, respectively. After subcutaneous administration, peak plasma levels are reached in approximately 23 minutes. The terminal half-life is approximately 58 minutes for intramuscular administration and 59 to 64 minutes for subcutaneous administration. The apparent volume of distribution is 0.15––0.3 L/kg.