Teriparatide

Teriparatide is a synthetic analogue of parathyroid hormone, specifically the biologically active amino-terminal portion of the hormone, and belongs to the class of bone-forming agents used to treat osteoporosis. It acts on parathyroid hormone receptors in bone, stimulating bone formation when administered intermittently at prescribed doses. This increases bone mineral density and can improve bone strength, helping reduce the risk of certain fractures in appropriately selected patients. Teriparatide is primarily used for adults with osteoporosis who have a high risk of fracture or who cannot adequately use other osteoporosis treatments. It is administered as a subcutaneous injection, usually once daily, into the thigh or abdominal area. Unlike medicines that primarily slow bone breakdown, teriparatide promotes new bone formation, although its effects depend on appropriate treatment selection, adherence, and adequate calcium and vitamin D intake. Treatment requires assessment of fracture risk, calcium balance, kidney function, relevant medical history, and other medicines. Possible adverse effects include nausea, joint or limb pain, dizziness, and temporary changes in blood calcium levels. Because certain bone disorders and previous skeletal radiation may affect suitability, clinicians must assess individual risk factors before prescribing. Teriparatide is not appropriate for every patient with osteoporosis, and treatment duration and follow-up should be determined according to current prescribing guidance and the patient's ongoing fracture risk.

Teriparatide was developed as a recombinant form of the active amino-terminal portion of human parathyroid hormone for the treatment of osteoporosis. Research established that intermittent administration of this hormone fragment stimulates bone-forming cells and can increase bone mineral density. The United States Food and Drug Administration (FDA) approved the reference teriparatide product in 2002 for osteoporosis treatment. The European Commission granted marketing authorisation for Forsteo, a teriparatide-containing medicine, on June 10, 2003. Subsequent clinical studies evaluated its effects in postmenopausal women, men with osteoporosis, and patients with glucocorticoid-associated osteoporosis. Additional teriparatide products, including biosimilar medicines, have since received authorisation in various regions. Regulatory indications, treatment duration, and product-specific instructions may differ between countries, so the applicable local prescribing information should be checked.

Teriparatide is used to treat osteoporosis in adults who have an increased risk of fractures. In the United States, approved uses include postmenopausal women with osteoporosis at high fracture risk or who have failed or cannot tolerate other osteoporosis therapies, men with primary or hypogonadal osteoporosis at high fracture risk or who have failed or cannot tolerate other available therapies, and men and women with osteoporosis associated with sustained systemic glucocorticoid treatment who are at high fracture risk. European indications include treatment of osteoporosis in postmenopausal women and men at increased fracture risk, as well as glucocorticoid-associated osteoporosis in women and men at increased risk. Teriparatide is generally administered as a single agent during its bone-forming treatment course. Following completion, clinicians may prescribe an antiresorptive osteoporosis medicine to help maintain gains in bone density, depending on the patient's clinical needs and applicable treatment guidance.

The usual adult dose is 20 micrograms administered subcutaneously once daily into the thigh or abdominal area. It is not intended for intravenous or intramuscular administration. Patients or caregivers should receive training in the correct use of the prescribed injection device, including safe injection technique, storage, handling, and disposal. The initial dose should be given in circumstances where the patient can sit or lie down if dizziness or postural hypotension occurs. Adequate calcium and vitamin D intake should be maintained, with supplementation based on individual dietary intake and clinical assessment. Under US prescribing information, treatment beyond two years over a patient's lifetime should be considered only when the patient remains at, or returns to, a high risk of fracture. Local product guidance may specify different duration restrictions. Treatment response, tolerability, calcium status, and ongoing fracture risk should guide follow-up and decisions about subsequent osteoporosis therapy.

Common adverse effects of teriparatide include pain in the limbs, joint pain, nausea, headache, dizziness, muscle cramps, and discomfort at the injection site. Some patients experience temporary increases in blood calcium levels or dizziness when standing, particularly after initial doses. Symptoms vary in type and severity between individuals and may improve with appropriate supportive measures. Patients should be counselled to sit or lie down if they experience light-headedness after injection and to report persistent, worsening, or troublesome symptoms to their healthcare professional. Treatment should not be modified or discontinued without appropriate clinical advice.

Important risks associated with teriparatide include hypercalcaemia, worsening of certain calcium-related disorders, urolithiasis, orthostatic hypotension, and rare serious hypersensitivity reactions. Treatment should generally be avoided in patients with conditions that increase the risk of osteosarcoma, including Paget's disease of bone, skeletal malignancy or bone metastases, previous radiation therapy involving the skeleton, and certain hereditary predispositions. It should not be used in patients with an underlying hypercalcaemic disorder or known hypersensitivity to the product. Patients with active or recent kidney stones require careful assessment because treatment may increase the risk of recurrence. Severe allergic reactions, fainting, or symptoms suggesting significant hypercalcaemia require prompt medical evaluation. If serious toxicity develops, the prescriber should reassess treatment and consider interruption or discontinuation according to the nature and severity of the event and the applicable product information.

Before starting teriparatide, clinicians should assess fracture risk, medical history, serum calcium, renal function, and relevant markers of bone metabolism where indicated. Additional evaluation may be required for patients with kidney stones, unexplained elevations in alkaline phosphatase, metabolic bone disorders, or previous skeletal radiation. Calcium and vitamin D intake should be reviewed to avoid inadequate intake or excessive supplementation. Teriparatide is not recommended during pregnancy, and breastfeeding is generally avoided during treatment according to the applicable product information. Safety and effectiveness are not established for routine paediatric use, and treatment is avoided in patients whose bones are still developing. Digoxin requires particular attention because teriparatide-associated increases in serum calcium may increase the risk of digitalis toxicity. Other medicines and supplements that influence calcium balance should also be reviewed. Patients with significant renal impairment require individual assessment because altered calcium handling and underlying bone disease may affect treatment suitability.

Confirm that the patient has an appropriate indication and elevated fracture risk before initiating treatment. Review baseline calcium status, renal function, vitamin D adequacy, history of nephrolithiasis, and risk factors for skeletal malignancy or osteosarcoma. Demonstrate injection-device use and provide clear instructions on daily administration, storage, handling, and device replacement according to the specific product label. Advise patients about possible dizziness after injection and recommend administering initial doses where they can sit or lie down if symptoms develop. Review digoxin and other medicines that may affect calcium levels, and arrange laboratory monitoring according to individual risk and local guidance. Assess adherence, new symptoms, fracture history, and treatment response during follow-up. Plan the next stage of osteoporosis management before teriparatide is stopped, as subsequent antiresorptive treatment may be appropriate to preserve improvements in bone density. Coordination between the prescribing clinician, pharmacist, and other members of the care team supports safe administration and continuity of treatment.