Teriparatide is a human parathyroid hormone analog with the same structure as the N-terminal 34 amino acid sequence of native parathyroid hormone (PTH). It binds to the PTH-1 receptor and exerts a physiological role in bones and kidneys, while there is no adverse effect of the C-terminal peptide on bone metabolism. Teriparatide is the first drug approved by the FDA for the treatment of osteoporosis and the promotion of bone formation. The drug has been shown to increase osteoblast activity, thereby promoting the formation of new trabecular and cortical bones. It ultimately increases bone mass and bone strength and reduces the risk of vertebral and non-vertebral fractures.
Teriparatide is recombinant human parathyroid hormone (rhPTH) 1-34. Similar to endogenous PTH, it can interact with specific high-affinity cell surface receptors to exert physiological effects. Teriparatide improves the trabecular bone microstructure and increases bone mass and bone strength by stimulating new bone formation in cancellous and cortical bone. Endogenous PTH is a major regulator of calcium and phosphate metabolism in bone and kidney. Its physiological functions include regulation of bone metabolism, reabsorption of calcium and phosphate by the renal tubules, and intestinal calcium absorption.
In patients with osteoporosis, subcutaneous injection of teriparatide can rapidly increase the level of serum bone formation markers and delay the increase of bone resorption markers. Short-term application can significantly improve lumbar spine bone mineral density. Teriparatide stimulates osteoblast activity in patients with primary osteoporosis and relatively inhibits osteoclast function, thereby promoting bone formation.
Pharmacokinetics and metabolism
Teriparatide is widely absorbed after subcutaneous injection, with the absolute bioavailability of approximately 95%, and the absorption and elimination are rapid. The peak of blood is reached in about 30 minutes after subcutaneous injection of 20 ug, and drops to an undetectable level within 3 hours. Studies on the metabolism or excretion of this product have not been carried out, and it may be metabolized in the liver by a non-specific enzymatic mechanism similar to PTH, and then excreted via the kidney. The half-life of serum administered by intravenous injection of teriparatide is 5 minutes, and the half-life of subcutaneous injection is about 1 hour.
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