Final answer:
Tenofovir, an antiviral medication used to treat HIV and hepatitis B infections, can cause Fanconi syndrome, decreased bone mineral density, and osteomalacia due to kidney damage leading to hypophosphatemia and hypocalcemia.
Step-by-step explanation:
The drug that can cause Fanconi syndrome, a decrease in bone mineral density, and osteomalacia is tenofovir. Tenofovir is an antiviral medication used to treat HIV and chronic hepatitis B infections. This drug has been associated with kidney damage that can lead to Fanconi syndrome, which is characterized by the inability of the renal proximal tubules to reabsorb electrolytes and nutrients back into the bloodstream, resulting in conditions such as hypophosphatemia (low phosphate levels) and, consequently, hypocalcemia due to vitamin D3 deficiency.
Decreased phosphate levels compromise bone health, leading to reduced bone mineral density and osteomalacia, the softening of the bones. While bisphosphonates are often prescribed to treat bone diseases like osteoporosis, they are not implicated in causing Fanconi syndrome.
Instead, bisphosphonates decrease the activity of osteoclasts and can help maintain bone density, although long-term use beyond 3-4 years may lead to an increased risk of bone fractures due to the old bone becoming brittle.