Drugmaker ViroPharma Inc. on Wednesday said fourth-quarter earnings fell 75 percent as net product sales decreased.

Net income totaled $18 million, or 25 cents per share, versus $72.7 million, or $1.17 per share in the year-ago period.

Revenue fell 5 percent to $38.6 million from $40.5 million in the prior-year quarter. Net product sales for its Vancocin treatment for intestinal bacterial infections fell 5 percent to $38.5 million, while milestone and license fee revenue was steady at $141,000.

Total costs and expenses increased 10 percent to $13.5 million, with marketing, general and administrative costs more than doubling to $7.1 million.

Analysts polled by Thomson Financial expected net income of 20 cents per share on revenue of $40 million.

For the year, net income fell 41 percent to $66.7 million, or 95 cents per share, from $113.7 million, or $2.02 per share in 2005.

Revenue grew 26 percent to $167.2 million from $132.4 million in 2005.

ViroPharma shares fell $1.60, or 9.8 percent, to $14.87 in morning trading on the Nasdaq.