Brief Answer: Alendronate reduces calcium removal from bones Detailed Answer: Hi Young Lady, Thanks for your query. In order to understood better, the mechanism of action of alendronate, it would be helpful to know the composition and physiology of bone. A bone consists of a mesh-like structure, called Matrix, in which calcium is deposited. Strength of the bone depends on matrix and quantity of calcium deposits in the bone. There is continuous process of remodeling of the bone, primarily by the action of two types of cells:- 1. Osteoblasts, which help in deposition and distribution of calcium in the bone (you can call it as 'bone building') and, 2. Osteoclasts, which are responsible for removing aged component of bone and, calcium from the bone. The process is called bone resorption. The delicate balance between the activities of these cells is mediated by a complex process, which involves hormones- among others. The bone undergoes thinning and the bone density is reduced ((called osteoporosis), and thereby become fragile, weak and fracture-prone if the activity of osteoclasts exceeds that of osteoblasts. In view of the above, ALENDRONATE (and related products) belong to the Class of Medicines called Bisphosphonates, which strengthen the bones by inhibiting bone resorption by osteoclasts. Hence, in clinically significant osteoporosis, treatment is directed towards:- * promoting bone strength by increasing calcium deposition (through additional Calcium + Vitamin D supplements) and, * reducing bone resorption by inhibiting osteoclasts by Bisphosphonates. Hope I have addressed to your concerns to your complete satisfaction and you find my response helpful and informative. I will be happy to answer further queries, if any. Take care, Col (Dr.) Rakesh Karanwal

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