In a previous note, Evans argued that Protonix has been used largely because it is priced lower that Prilosec.

FORBES: Wyeth's Diet Drug Risk Gets Fatter

He points out that Wyeth's largest products, including the antidepressant Effexor and Protonix, for ulcers, are the ones growing the fastest.

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He rates the stock "underperform, " although he does see strength in some of Wyeth's drugs, including Effexor for depression, Protonix for acid reflux, and pneumonia vaccine Prevnar.

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He thinks that sales of Protonix, an ulcer medicine, will be hurt by a generic version of AstraZeneca 's (nyse: AZN - news - people ) Prilosec.

FORBES: Wyeth's Diet Drug Risk Gets Fatter

Cheap, generic prilosec could still hurt Protonix sales eventually.

FORBES: Wyeth's Blowout Quarter

For the most part, Protonix, Prilosec and a third drug, Prevacid, which is sold by a joint venture of Abbott Laboratories (nyse: ABT - news - people ) and Japan's Takeda , are considered very similar.

FORBES: Magazine Article