TRENTON, N.J. (AP) — Shares of drugmaker Merck & Co. declined Monday after two analysts downgraded their ratings, mainly due to worries that results of patient studies could hurt prospects for a few drugs and drag down future revenue and profit.

The drugs involved are in two areas where Merck was a pioneer, eventually got hit with generic competition and has since been trying to regain leadership. The company invented the first widely used pills for treating osteoporosis, with its Fosamax, and controlling high cholesterol, with Mevacor, the first drug in the blockbuster class called statins that includes Pfizer Inc.’s Lipitor. Mevacor’s successor, Zocor, was an even bigger seller for Merck, with annual revenue of about $5 billion.