Irvine-based drug maker Anchen Pharmaceuticals Inc. is being acquired for $410 million by Par Pharmaceutical Companies Inc., Par said Wednesday.

Woodcliff Lake, N.J.-based Par has annual sales of just more than $1 billion. It said it was buying Anchen to expand its generic drug offerings.

Par and other generic makers are looking for deals with patent expirations coming up.

Anchen, which has about 220 workers, is a privately held specialty drug company that develops generic products on a niche basis.

It has five marketed products, including a generic version of Wellbutrin XL, a popular antidepressant, and one of Cipro, a drug that’s used to treat anthrax and bacterial infections.

Par said that Anchen is profitable and expects to launch eight to 10 niche generic drugs over the next two years.

The deal is expected to close by the end of 2011. Par is using cash and a $350 million loan to buy Anchen.