1. Clinical Overview
Calcitonin (Salmon) is a synthetic polypeptide hormone identical to salmon calcitonin. It acts as a potent inhibitor of osteoclastic bone resorption, leading to a rapid decrease in serum calcium levels. It is used primarily for the treatment of postmenopausal osteoporosis, Paget's disease of bone, and hypercalcemia. In the Indian context, it is a second-line or adjunctive therapy, especially where bisphosphonates are contraindicated or not tolerated.
| Onset | Duration | Bioavailability |
|---|---|---|
| Onset of hypocalcemic effect: Within 2 hours of parenteral administration. | Duration of hypocalcemic effect: 6 to 8 hours for a single injection. | Intranasal: Approximately 3% (range 0.3% to 30.6%). Subcutaneous/Intramuscular: ~70%. |
2. Mechanism of Action
Calcitonin binds directly and with high affinity to specific calcitonin receptors (CTRs) on osteoclasts. This binding activates adenylate cyclase and increases intracellular cAMP. The increased cAMP inhibits osteoclast motility and ruffled border formation, leading to a rapid and potent inhibition of bone resorption. It also promotes renal excretion of calcium, phosphate, sodium, and magnesium.
3. Indications & Uses
- Postmenopausal Osteoporosis (as adjunctive therapy)
- Paget's Disease of Bone (Osteitis Deformans)
- Hypercalcemia (of malignancy or other causes)
4. Dosage & Administration
Adult Dosage: Postmenopausal Osteoporosis: SC/IM: 100 IU daily or every other day. Nasal: 200 IU (one spray) daily in one nostril. Paget's Disease: SC/IM: 100 IU daily initially, maintenance 50 IU daily or 50-100 IU every other day. Hypercalcemia: SC/IM: 4 IU/kg every 12 hours; may increase to 8 IU/kg every 12 hours if response inadequate.
Administration: Parenteral: Rotate subcutaneous or intramuscular injection sites (thigh, abdomen). Nasal: Use one spray per day in alternating nostrils. Prime nasal spray before first use. Patient should be sitting upright, not tilt head back. Avoid blowing nose immediately after.
5. Side Effects
Common side effects may include:
- Nausea, vomiting (especially with parenteral route)
- Flushing of face, ears, hands
- Local injection site reactions (pain, swelling, redness)
- Nasal irritation, dryness, rhinitis (with nasal spray)
6. Drug Interactions
| Drug | Effect | Severity |
|---|---|---|
| Bisphosphonates (e.g., Alendronate, Zoledronic acid) | Additive hypocalcemic effect. Monitor serum calcium closely. | Moderate |
| Loop Diuretics (e.g., Furosemide) | May reduce the hypocalcemic effect of calcitonin. | Moderate |
| Lithium | Calcitonin may decrease serum lithium levels; monitor lithium levels. | Moderate |
| Calcium and Vitamin D Supplements | May antagonize the hypocalcemic effect. Space administration if used for osteoporosis. | Mild |
7. Patient Counselling
- Do use calcium and vitamin D supplements as prescribed by your doctor for osteoporosis (unless being treated for hypercalcemia).
- Do rotate injection sites to prevent local reactions.
- Do prime the nasal spray before first use.
- Don't stop medication abruptly without consulting your doctor.
- Don't use the nasal spray if you have a severe nasal infection or ulcer.
8. Toxicology & Storage
Overdose: Symptoms are extensions of pharmacologic effects: Severe nausea, vomiting, flushing, dizziness, and profound hypocalcemia leading to tetany, seizures, and cardiac arrhythmias.
Storage: Store unopened vials/sprays in a refrigerator at 2°C to 8°C. Do not freeze. Protect from light. After opening, some nasal sprays can be kept at room temperature (up to 25°C) for up to 30 days. Refer to specific brand's package insert. Keep out of reach of children.