Less than two months after reporting plummeting first-quarter revenues and earnings, Schering-Plough (NYSE:SGP) is at it again. Today, the drug company warned that second-quarter results will fall short of prior expectations. The remainder of the year's not looking a whole lot better, either.

For Q2, Schering now expects to earn $0.12 per share -- substantially below the $0.18 analysts had anticipated. For its fiscal second half, Schering cautioned that earnings could come in below the estimated $0.24 it will earn in the first two quarters. Analysts had been expecting $0.37 per share for Q3 and Q4 combined. For perspective, the company netted $1.42 per share for all of fiscal 2002.

Allergy drug Claritin remains a major source of Schering's pain, as generic over-the-counter competition continues to eat away at U.S. sales. And there's not much Schering can do to contain the damage. First-quarter U.S. sales of Claritin dropped 83%, to $109 million from $659 million a year ago, and while Schering didn't offer any guidance regarding Q2 sales, it won't likely be pretty.

Unfortunately the company's Hepatitis C treatment, Intron/Rebetrol, is likewise under siege in the marketplace and isn't taking up Claritin's slack.

As for its pipeline, Schering's top drugs occupy the allergy/respiratory and anti-infective/anti-cancer spaces. With both Claritin and Intron/Rebetrol representing these two divisions, Schering's results appear increasingly vulnerable to the effects of increased competition.

Bottom line: Despite its 3.7% dividend yield and balance sheet sporting a chunk of cash and little debt, investors should stay away from Schering-Plough -- at least for now. The company's drug pipeline doesn't appear to boast any guaranteed blockbusters, and its star drugs are struggling with relentless competition.

Who knows, Schering-Plough may indeed end up the turnaround story many hope for, but wait for more evidence before jumping in.