NEW YORK (CNN/Money) - J.P. Morgan analyst Carl Seiden cut earnings estimates for Schering-Plough on Friday, citing weakness in its family of allergy drugs, including Claritin and Clarinex, and cut his price target for the stock.

Schering (SGP: down $0.50 to $28.50, Research, Estimates) shares sank nearly 2 percent to about $28.50, near its low for the year.

Seiden kept his projections for the company's 2002 earnings, but cut his forecast for 2003 earnings to $1.60 from $1.80 a share, citing lingering concerns about manufacturing problems and "the cannibalization" of prescription Claritin and next-generation Clarinex by over-the-counter versions of the allergy drug that cost about a third of the price.

Seiden also said in a research note that longer term he sees "huge risks" to the base business, with all the company's growth riding on cholesterol treatment Zetia, which Schering is co-developing with Merck & Co (MRK: up $2.00 to $54.15, Research, Estimates).

He said his forecast of Zetia "assumes a perceived 'clean' side-effect profile, which recently has been implicated with certain blemishes," but added he is not yet concerned about this.

Seiden cut his 12-month price target for Schering to $31 from $35.

Schering-Plough is expected to report first-quarter earnings on April 18, and on average analysts surveyed by First Call are looking for a profit of 41 cents per share.