Which of the following drugs is both anti-receptive and bone formative?
Ans. is 'a' i.e., Strontium Ranelate Osteoporosis is an abnormal decrease in amount of bone, but whatever left, is of normal quality. It results from bone loss due to age related changes in bone remodelling.In adult bones, remodelling is the principal metabolic skeletal process.During remodelling the bone is first resorbed by osteoclasts and is then replaced by an equal amount of bone tissue due to action of osteoblasts.This process of bone resorption and formation goes on throughout the adult life, and it serves two purposes.To repair the micro damage within the skeleton.To supply calcium from the skeleton to maintain serum calcium.In young adult the resorbed bone is replaced by an equal amount of new bone tissue. Thus the mass of skeleton remains constant after peak bone mass in achieved in adulthood.However after the age of 35-40 the resorption and formation processes becomes imbalanced and resorption exceeds formation.Excessive bone loss can be due to an increase in osteoclastic activity and or decrease in osteoblastic activity. Mechanism of action of Strontium Ranelate in the t/t of osteoporosis.Strontium Ranelate increases bone mass throughout the skeleton. It appears to be modestly anti resorptive while at the same time not causing much decrease in bone formation.Strontium is incorporated into hydroxyapatite replacing calcium, a feature that might explain some of its fracture benefit.* It is approved in several European countries for the t/t of osteoporosis.Pharmacological agents used to manage osteoporosis either act byDecreasing the rate of bone resorption (anti resorptive therapy.)Promoting bone formation (anabolic therapy).Since bone remodelling is a coupled process, anti resorptive drugs ultimately decrease the rate of bone formation and therefore do not promote substantial gains in BMD."Thus, Strontium ranelate is unique because it decreases osteoblastosis as well as promote bone formation. "More on t/t of osteoporosisPharmacological treatment of osteoporosis is generally aimed at restoring bone strength and preventing fractures.The long standing centrepiece of this approach has been anti resorptive drugs such as: -BiphosphonateEstrogenSelective estrogen receptor modulator, RaloxifeneCalcitoninUntil recently, anti resorptive drugs were the only drugs approved in the United States for treating osteoporosis.This situation changed in 2002 when FDA approved Teriparatide (the biologically active PTH fragment). Teriparatide acts by increasing the bone massBecause teriparatide stimulates bone formation whereas biphosphonates reduce bone resorption, it was predicted that therapy combining the two would enhance the effect on bone marrow density more than treatment with either one alone.However addition of teriparatide to alendronate provided no additional benefit for bone mass density.Before the advent of strontium Ranelate there wasn't any drug which combined the two processes i.e., increasing bone formation and at the same time, decreasing bone resorption.Strontium Ranelate has a novel mechanism of action for an osteoporotic drug as it acts on bone resorption to reduce the rate of bone growth but also acts on bone formation promoting the growth of new bone.More on anti resorptive therapies for osteoporosis:BisphosphonatesAlendronate, PamidronateMost effective drugs currently approved for prevention and t/t of osteoporosis.They suppress bone resorption at doses that do not inhibit mineralization.Thiazide diureticsThey are not strictly anti resorptive but they reduce urinary Ca2+ excretion and constrain bone loss in patients with hypercalciuria.EstrogenThere is an unambiguous relationship between estrogen deficiency and osteoporosis. Post-menopausal status or estrogen deficiency at any stage significantly increases patient's risk for osteoporosis.Selective Estrogen receptor modulator (SERM)These are estrogenic compounds with tissue selective activities.Raloxifene (SERM) acts as an estrogen agonist on bone and liver and is inactive on the uterus.CalcitoninCalcitonin inhibits osteoclastic bone resorption.
Strontium ranelate
Calcitonin
Ibadronate
Teriperatide
Endocrinology