By Val Brickates Kennedy

Drug stocks inched lower in early trading Friday, as shares of Allergan Inc. (AGN) gained after the company issued a positive second-quarter earnings report.

The NYSE Arca Pharmaceutical Index and the NYSE Arca Biotechnology Index were both down marginally at 279.33 and 875.41, respectively.

Shares of Botox-maker Allergan climbed 3% to $54.14. Allergan said Friday its second-quarter earnings rose to $176.1 million, or 58 cents a share, from $143.4 million, or 47 cents a share, in the year-earlier period.

Excluding various items, Allergan would have posted adjusted earnings of 75 cents a share compared to the year-earlier 63 cents. Revenue for the quarter slipped to $1.13 billion from $1.17 billion.

Analysts polled by FactSet were expecting earnings of 67 cents a share, on average.

The Irvine, Calif.-based company also issued its financial forecast. It now sees adjusted earnings of 67 cents to 69 cents a share for the third quarter and $2.71 to $2.75 a share for the full year. According to FactSet, Wall Street is expecting per-share earnings of 72 cents for the third quarter and $2.70 for the full year.

Shares of Endo Pharmaceuticals (ENDP) advanced 4% to $21.66. On Thursday, Endo said that while its second-quarter profit fell on various charges, revenue rose 22% to $373 million.

Excluding various items, Endo would have reported adjusted earnings of 73 cents a share versus 59 cents for the 2008 period. Endo also said it believes it will be able to hit the upper end of its 2009 adjusted earnings forecast of $2.59 to $2.67 a share.

Merck & Co. (MRK) shares were up almost 2% to $30.39.

On Thursday, Sanofi-Aventis (SNY) said it was buying Merck's stake in their animal-health joint venture Merial Limited for $4 billion. Merck was expected to divest the venture as part of its impending merger with Schering-Plough Corp. (SGP), which also has a sizeable animal health-care business.

-Val Brickates Kennedy; 415-439-6400; AskNewswires@dowjones.com