Calcitonin

• Postmenopausal Osteoporosis
• Paget's Disease of Bone
• Hypercalcemia
• Bone Pain from Fractures

Calcitonin-salmon is a synthetic form of calcitonin, a naturally occurring hormone involved in calcium regulation and bone metabolism. This medication is used for the treatment of postmenopausal osteoporosis and Paget's disease of bone, providing both anti-resorptive effects and analgesic properties for bone pain.

Mechanism of Action

Calcitonin is a 32-amino acid peptide hormone that primarily acts on osteoclasts to inhibit bone resorption. The salmon form is used therapeutically because it is more potent and has a longer duration of action than human calcitonin. Calcitonin binds to specific receptors on osteoclasts, causing them to lose their ruffled borders and reduce their resorptive activity. This results in decreased release of calcium and phosphorus from bone, leading to a reduction in serum calcium levels and inhibition of bone turnover. Additionally, calcitonin has analgesic effects, possibly through direct effects on the central nervous system, making it particularly useful for bone pain.

Available Formulations

Calcitonin-salmon is available as a nasal spray (200 IU/spray) and as an injection (200 IU/mL). The nasal spray is administered into alternating nostrils daily. The injectable form can be given subcutaneously or intramuscularly. The nasal spray should be primed before first use and stored in the refrigerator before opening, then at room temperature for up to 35 days after opening.

Medical Uses

Calcitonin-salmon is FDA-approved for the treatment of postmenopausal osteoporosis in women more than 5 years postmenopause (nasal spray) and for Paget's disease of bone, hypercalcemia, and postmenopausal osteoporosis (injection). Due to an increased risk of malignancy seen in clinical trials, the nasal spray should be reserved for patients who cannot or will not take other osteoporosis medications. The analgesic effect makes it useful for acute vertebral fracture pain. It is considered a second-line agent for osteoporosis.

Dosing Guidelines

For postmenopausal osteoporosis using nasal spray, the recommended dose is 200 IU (one spray) daily, alternating nostrils. For injectable administration, 100 IU daily or every other day is typical for osteoporosis. For Paget's disease, 50-100 IU daily or every other day is used initially, with dose reduction possible after response. For hypercalcemia, 4 IU/kg every 12 hours may be increased to 8 IU/kg every 6-12 hours. Adequate calcium and vitamin D intake should be ensured during treatment.

Important Safety Information

An increased risk of malignancy has been observed with calcitonin-salmon use. The FDA advises that the nasal spray should be reserved for patients who cannot use other osteoporosis therapies. Hypersensitivity reactions, including anaphylaxis, have been reported; a skin test may be considered before treatment in patients with suspected sensitivity. Nasal adverse effects (rhinitis, epistaxis, nasal irritation) are common with the spray. The medication should be discontinued if severe nasal ulceration occurs. Antibody formation may reduce effectiveness over time.

Drug Interactions

Calcitonin-salmon has minimal significant drug interactions. Lithium may reduce the hypocalcemic effect of calcitonin. The medication may enhance the hypocalcemic effect of other agents that lower calcium (bisphosphonates, denosumab). Concurrent use with other bone-active agents should be approached with caution due to potential additive effects on bone metabolism. No significant CYP450 interactions are expected.

Where Calcitonin Fits Today

Calcitonin-salmon is now a niche drug. For osteoporosis it reduces vertebral fracture risk modestly and has no demonstrated effect on hip or other non-vertebral fractures, which places it behind every other approved class: oral bisphosphonates such as alendronate, intravenous zoledronic acid, denosumab, raloxifene, and the anabolic agents. The malignancy signal described above narrowed its place further, and current osteoporosis guidance summarized by NIAMS does not list it among the usual first- or second-line options. The realistic uses that remain are short-term pain relief after an acute vertebral compression fracture, where its analgesic effect is distinct from its bone effect and is typically used for a few weeks; a patient who cannot take or has failed every other agent; and the injectable form as a rapid, short-acting bridge in hypercalcemia while longer-acting therapy takes hold, since its calcium-lowering effect fades within days as receptors down-regulate.

Practical Points and Monitoring

The nasal spray is easy to use badly. Doses are alternated between nostrils, the bottle must be re-primed after any period of disuse, and nasal irritation or crusting is the usual reason for stopping; a nasal examination at follow-up catches ulceration early. Loss of effect over time is real, so a patient who was responding and then stops responding is more likely developing neutralizing antibodies than doing anything wrong. When it is used for fracture pain, an end date is set at the start so that it does not drift into indefinite use. The MedlinePlus calcitonin monograph covers the patient instructions for both forms.

Because the drug is weak, it is never a reason to defer a more effective agent. A patient started on calcitonin for post-fracture pain is transitioned to a bisphosphonate or denosumab as soon as the acute period passes, and calcium and vitamin D are repleted from day one. Bone density is followed on the same schedule as any other osteoporosis treatment, and a new fracture on calcitonin is treated as failure of the regimen rather than a reason to continue. Our endocrine team manages this transition, and the article on bone health after 50 covers the fundamentals that every agent depends on. Patients with osteopenia rarely have a reason to use it at all.

Special Populations

There are no adequate studies in pregnant women; animal studies showed decreased fetal birth weights. Calcitonin does not cross the placenta and is unlikely to affect the fetus, but use only if clearly needed. It is unknown whether calcitonin-salmon is excreted in human breast milk; calcitonin has been shown to inhibit lactation in animals. Safety and efficacy have not been established in pediatric patients. Elderly patients may be more susceptible to nasal adverse effects. No dose adjustment is needed for renal or hepatic impairment. Patients should be tested for hypersensitivity before initiating therapy.