Which of the following drugs acts by increasing bone formation & inhibiting bone resorption
**Core Concept**
The question is testing the student's understanding of the pharmacological mechanism of action of drugs used in the treatment of osteoporosis. Specifically, it is asking for a drug that increases bone formation and inhibits bone resorption, which are key processes in maintaining bone health.
**Why the Correct Answer is Right**
The correct answer is **Bisphosphonates**. Bisphosphonates work by inhibiting osteoclast-mediated bone resorption, which is the process by which bone is broken down and released into the bloodstream. At the same time, they also stimulate bone formation by promoting the activity of osteoblasts, the cells responsible for bone building. This dual action leads to an overall increase in bone density and strength.
**Why Each Wrong Option is Incorrect**
* **Option A:** Estrogen replacement therapy (ERT) may have some beneficial effects on bone density, but it primarily works by inhibiting osteoclast activity, rather than stimulating bone formation.
* **Option C:** Risedronate is a bisphosphonate, but the question is asking for a drug that increases bone formation, which is not a primary action of bisphosphonates.
**Clinical Pearl / High-Yield Fact**
Bisphosphonates are a class of drugs that are commonly used in the treatment of osteoporosis, particularly in postmenopausal women and men with low bone density. They are also used to treat other bone diseases, such as Paget's disease and osteogenesis imperfecta.
**Correct Answer:** B. Bisphosphonates.