1. Clinical Overview
Calcitonin (Salmon) is a synthetic polypeptide hormone identical to salmon calcitonin. It is a potent inhibitor of osteoclastic bone resorption, leading to a rapid decrease in serum calcium levels. It also has analgesic properties in conditions like Paget's disease and vertebral fractures. In India, it is primarily used for the short-term management of hypercalcemia and as an adjunctive therapy for Paget's disease and postmenopausal osteoporosis, though its use has declined with the advent of more potent antiresorptives like bisphosphonates.
| Onset | Duration | Bioavailability |
|---|---|---|
| Within 15 minutes for hypocalcemic effect; analgesic effect may take several days to weeks. | Hypocalcemic effect: 6 to 8 hours for a single injection. Full therapeutic effects for bone conditions require sustained treatment. | Approximately 70% after intramuscular (IM) or subcutaneous (SC) injection. Intranasal bioavailability is significantly lower, around 3%. |
2. Mechanism of Action
Calcitonin binds with high affinity to specific calcitonin receptors (CTRs) on osteoclasts and renal tubular cells. In bone, it directly inhibits osteoclastic activity and proliferation, reducing bone resorption and hydroxyproline release. In the kidney, it increases the excretion of calcium, phosphate, sodium, magnesium, and chloride by reducing their tubular reabsorption. It may also have a central analgesic effect by increasing beta-endorphin levels and modulating pain pathways.
3. Indications & Uses
- Short-term management of symptomatic Paget's disease of bone (osteitis deformans)
- Short-term treatment of hypercalcemia (especially malignancy-associated)
- Postmenopausal osteoporosis (as an adjunct to calcium and vitamin D, to prevent bone loss and reduce fracture risk)
4. Dosage & Administration
Adult Dosage: Paget's Disease: 100 IU daily via SC or IM injection. Maintenance: 50 IU daily or 50-100 IU every other day. Hypercalcemia: 4 IU/kg body weight every 12 hours via SC or IM; may increase to 8 IU/kg every 12 hours if response inadequate. Max: 8 IU/kg every 6 hours. Postmenopausal Osteoporosis: 100 IU daily via SC or IM injection or 200 IU (one spray) intranasally daily.
Administration: For SC/IM Injection: Reconstitute lyophilized powder with the provided sterile diluent. Administer via deep subcutaneous or intramuscular injection, rotating sites (thigh, abdomen, buttock). Intranasal: Use only if specifically prescribed; prime pump before first use. Alternate nostrils daily. Store reconstituted solution in refrigerator and use within 24 hours.
5. Side Effects
Common side effects may include:
- Nausea (with or without vomiting)
- Flushing of face, ears, hands
- Local injection site reactions (pain, redness, swelling)
- Anorexia
6. Drug Interactions
| Drug | Effect | Severity |
|---|---|---|
| Lithium | Calcitonin may reduce serum lithium levels, potentially decreasing its efficacy. Monitor lithium levels. | Moderate |
| Loop Diuretics (e.g., Furosemide) | Concurrent use may potentiate the hypocalcemic effect. Monitor serum calcium closely. | Moderate |
| Bisphosphonates (e.g., Alendronate) | Additive hypocalcemic and bone resorption inhibition effects. Use combination with caution and monitor calcium. | Moderate |
| Vitamin D and Calcium Supplements | May antagonize the hypocalcemic effect of calcitonin. In osteoporosis therapy, they are used as adjuncts, but timing may need separation. | Mild |
7. Patient Counselling
- Do rotate injection sites to prevent local skin reactions.
- Do report any signs of allergy (rash, itching, swelling, dizziness) immediately.
- Do ensure adequate calcium and vitamin D intake as advised by your doctor for osteoporosis.
- Don't stop the medication abruptly without consulting your doctor.
- Don't use if the reconstituted solution is discolored or contains particles.
8. Toxicology & Storage
Overdose: Symptoms are primarily related to excessive hypocalcemia: paresthesias (tingling), muscle twitching, tetany, seizures, cardiac arrhythmias, and hypotension. Nausea and vomiting may be severe.
Storage: Store unopened vials/pens at 2°C to 8°C (in a refrigerator). Do not freeze. Protect from light. After reconstitution, the solution should be used immediately. If necessary, it may be stored in the refrigerator (2°C to 8°C) for up to 24 hours. Do not use if the solution is discolored or contains particulate matter.