Eli Lilly and Co. said its quarterly earnings plunged 58 percent, hurt by special charges and generic competition for its Cymbalta depression drug, but it affirmed its earlier full-year profit forecast.

The U.S. drugmaker on Thursday said it had earned $501 million, or 47 cents per share, in the third quarter. That compared with $1.20 billion, or $1.11 per share, a year earlier.

Excluding special items such as charges of $95 million from research collaborations, Lilly earned 66 cents per share. Analysts on average expected 67 cents, according to Thomson Reuters I/B/E/S.

Sales fell 16 percent to $4.88 billion, but topped Wall Street's expectations of $4.83 billion.

Lilly's sales and earnings have suffered since late 2011, when its top-selling Zyprexa schizophrenia drug lost U.S. patent protection and faced competition from cheaper generics.

The pain worsened last December, when Lilly lost U.S. patent protection on Cymbalta, then its biggest drug. And its osteoporosis treatment Evista began facing cheaper generics in March.

Cymbalta sales fell 73 percent in the third quarter to $368 million, while Evista's tumbled 65 percent to $90 million.