Merck & Co. says its third-quarter profit plunged 35 percent because of competition from generic drugs, lower sales of its top-selling medicine, and restructuring and acquisition charges.

The world’s third-biggest drugmaker says net income was $1.12 billion, or 38 cents per share, down from $1.73 billion, or 56 cents per share, a year earlier.

The maker of Type 2 diabetes pill Januvia says that excluding the one-time items, net income would have been $2.73 billion, or 92 cents per share. Analysts surveyed by FactSet were expecting 88 cents per share.

Revenue totaled $11.03 billion, down 4 percent. That missed expectations for $11.13 billion in revenue.

The company lowered its 2013 profit forecast to $1.61 to $1.79 per share, from its July forecast of $1.84 to $2.05.