Actonel (P&G's drug) and Fosamax (Merck's drug) both reduce bone turnover, the rate at which bone material degenerates or breaks down. Fosamax tends to reduce bone turnover by a larger amount (60 percent or more) compared to roughly 50 percent for Actonel. P&G sought to demonstrate, however, that once a drug reduces bone turnover by a certain "threshold" amount—roughly 30 to 40 percent—any further reduction in bone turnover is not really significant because it does not actually result in fewer bone fractures.