Delivery of parathyroid hormone for the treatment of osteoporosis.

Parathyroid hormone (PTH), along with its fragments and analogues, potently restores bone mass and biomechanical strength in animal models of osteoporosis, and reduces fractures by up to 65% in clinical trials in osteoporotic patients. Despite this demonstrated efficacy, patient acceptance and compliance with PTH is limited by the need for daily subcutaneous injections. The development of an equally efficacious, noninjectable form of PTH would significantly expand the present market. A challenge to the development of an alternative delivery system is the requirement for low-dose, daily, intermittent pulses of PTH to induce the anabolic actions on bone. In this review, recent basic and clinical efforts to deliver PTH by oral, buccal, sublingual, transdermal, nasal and pulmonary approaches will be addressed.