Teriparatide Initiation Protocol and Mechanism of Action
Teriparatide should be initiated as a 20 mcg subcutaneous injection once daily, administered in the thigh or abdominal region, with concurrent calcium and vitamin D supplementation. 1
Mechanism of Action
- Teriparatide is an anabolic (bone-forming) agent consisting of the first 34 amino acids of the N-terminal region of parathyroid hormone 2
- Unlike anti-resorptive medications that prevent bone loss, teriparatide stimulates new bone formation, improving bone mineral density (BMD) and microarchitecture 2, 3
- It creates an "anabolic window" with a rapid increase in bone formation markers followed by a later increase in bone resorption markers 4
- The pharmacokinetics show rapid absorption (peak blood level at approximately 15 minutes) with a short half-life (about 1 hour) 4
Indications for Use
- Treatment of postmenopausal women with osteoporosis at high risk for fracture (defined as having a history of osteoporotic fracture or multiple risk factors) 1
- Increasing bone mass in men with primary or hypogonadal osteoporosis at high risk for fracture 1
- Treatment of osteoporosis associated with sustained systemic glucocorticoid therapy in men and women at high risk for fracture 1
- Reserved for patients with severe osteoporosis who have failed or cannot tolerate first-line therapies like bisphosphonates 5, 6
Administration Protocol
- Administer 20 mcg subcutaneously once daily in the thigh or abdominal region 1
- Initial administration should occur where the patient can sit or lie down in case of orthostatic hypotension 1
- Patients should receive proper training on using the delivery device (pen) 1
- Each pen contains 28 daily doses (620 mcg/2.48 mL) and can be used for up to 28 days 1
- Store the pen under refrigeration at 2°C to 8°C (36°F to 46°F) at all times 1
- Do not freeze the medication or transfer contents to a syringe 1
Supplementation Requirements
- All patients should receive supplemental calcium (1,000-1,200 mg/day) and vitamin D (600-800 IU/day) 5, 1
- Optimize calcium and vitamin D levels before starting therapy 5
Contraindications
- Hypersensitivity to teriparatide or its excipients 1
- Patients with increased baseline risk of osteosarcoma, including:
- Open epiphyses (pediatric and young adult patients) 1
- Metabolic bone diseases other than osteoporosis, including Paget's disease 1
- Bone metastases or history of skeletal malignancies 1
- Prior external beam or implant radiation therapy involving the skeleton 1
- Hereditary disorders predisposing to osteosarcoma 1
- Pre-existing hypercalcemia or underlying hypercalcemic disorders 1
Duration of Treatment
- Treatment duration should not exceed 2 years during a patient's lifetime 1
- Extended use beyond 2 years should only be considered if a patient remains at or has returned to having a high risk for fracture 1
- After completing teriparatide therapy, patients should transition to an antiresorptive medication to preserve bone mass gains 3
Monitoring and Side Effects
- Monitor for symptoms of hypercalcemia (nausea, vomiting, constipation, lethargy, muscle weakness) 1
- Watch for orthostatic hypotension, especially during initial administration 1
- Patients should be informed about the theoretical risk of osteosarcoma, though increased risk has not been observed in human studies 1
- Long-term studies show sustained fracture reduction benefits even after discontinuation of therapy 7
Common Pitfalls to Avoid
- Avoid transferring medication from the pen to a syringe 1
- Do not use beyond the 28-day period after first use, even if solution remains 1
- Avoid leaving the pen out of refrigeration for extended periods 1
- Do not use in patients with cancer or history of malignancy prone to metastasize to bone 5
- Do not combine with bisphosphonates as this may diminish the anabolic potential of teriparatide 3