What is the difference between actonel, (risedronate) fosamax?

Similar, but differ: Both are bisphosphonate drugs, taken orally, which decrease bone breakdown by osteoclast cells, and therefore increase bone density (a marker of bone strength). Different dosing, but can be weekly or monthly for either in osteoporosis. Were used in tumors to or to bone-now drugs mostly given IV for that. Fosamax (alendronate) stays in the system and bone longer; was thought to be more GI irritating (maybe not).