Which drugs are known to reduce bone mass?

• A. H2 blockers
• B. Calcium supplements
• C. Glucocorticoids and anticonvulsants such as phenobarbital and phenytoin
• D. Vitamin D

Answer: (C)

The main concept here is that certain medications can cause bone loss (osteoporosis) by disrupting calcium balance or bone remodeling.

Glucocorticoids and enzyme-inducing anticonvulsants like phenobarbital and phenytoin lead to reduced bone mass through multiple mechanisms. Glucocorticoids directly suppress osteoblast function and survival, while promoting osteoclast activity, and they also decrease calcium absorption from the gut and increase its excretion by the kidneys. Over time, these effects tilt the balance toward bone resorption and weaken bone structure. Enzyme-inducing anticonvulsants accelerate the breakdown of vitamin D, reducing intestinal calcium absorption and triggering secondary hyperparathyroidism, which further promotes bone loss. Additionally, prolonged use of these drugs is a well-known risk factor for osteoporosis.

Calcium supplements and vitamin D typically support bone health by improving mineral availability and absorption, so they are not associated with reduced bone mass. H2 blockers do not have a strong, direct, and consistent effect on bone mass compared with the drugs listed in the correct option.