Wyeth

(WYE)

beat first-quarter estimates Wednesday and boosted full-year earnings guidance.

The Madison, N.J., pharma giant said latest-quarter results were aided by a 12% rise in sales of its Effexor antidepressant. But Wyeth said domestic sales growth in the drug would flatten out this year as the class faces increasing scrutiny over possible dangerous side effects.

For the first quarter, Wyeth earned $1.08 billion, or 80 cents a share, on revenue of $4.58 billion. Analysts predicted a profit of 77 cents a share on revenue of $4.46 billion. For the same period last year, Wyeth earned $749.7 million, or 55 cents a share, on revenue of $4.01 billion.

The results were sufficiently strong to prompt the company to predict it would exceed its previous $2.70-to-$2.80-a-share full-year pro forma earnings target. Now, Wyeth says "it is likely that the upper end of the range will be exceeded." Finance chief Ken Martin said Wyeth would renew guidance at the end of the second quarter.

The company said Effexor recorded first-quarter sales of $868 million, up 12% over the same period last year. Sales growth is "moderating," partly because of "negative publicity" regarding antidepressants.

In mid-October, the Food and Drug Administration told Wyeth and the makers of other antidepressants to place a so-called black box warning on the drug labels, telling doctors to beware of prescribing these drugs to children and adolescents.

The black box warning -- the toughest required by the FDA -- said such medications "increase the risk of suicidal thinking and behavior in children and adolescents with major depressive disorders and other psychiatric disorders." The FDA adds that doctors contemplating prescribing an antidepressant for a child or adolescent "must balance the risk of increased suicidality with the clinical need."

Effexor and most antidepressants have never received FDA approval for use by children and adolescents, but doctors are permitted by law to make "off-label" prescriptions as long as a drug is approved for a single disease or condition.

A Wyeth spokesman said Wednesday that off-label use accounts for just 1% of total Effexor prescriptions. Wyeth made the labeling changes last month.

Bernard Poussot, president of Wyeth's pharmaceuticals division, told

TheStreet.com

Wednesday that he expects Effexor's U.S. sales growth to be "pretty flat" this year. Total Effexor growth should be in the "mid-single digits," thanks to healthy sales in Europe and Asia.

Poussot added that it is "difficult to predict" when U.S. sales growth might turn around. He told analysts during a telephone conference call that Wyeth has initiated a new Effexor promotion program to help identify potential patients earlier in their bouts with depression.

In terms of total prescriptions, Effexor remains the third-largest antidepressant in the U.S. market, according to IMS Health and A.G. Edwards. The leader is Zoloft from

Pfizer

(PFE) - Get Report

, followed by Lexapro from

Forest

(FRX)

.

A recent A.G. Edwards report notes that Effexor and several top-selling brand name antidepressants have failed to capitalize on the FDA's seizure of shipments of Paxil CR, a controlled-release antidepressant made by

GlaxoSmithKline

(GSK) - Get Report

. The FDA said it acted because the company had failed to improve manufacturing practices, and Paxil CR will remain off the market until the company complies.

As for other major products, Wyeth said sales of Prevnar, a vaccine to prevent pneumococcal disease in infants and children, more than doubled to $391 million. But sales of the Premarin family of drugs for treating menopausal symptoms dropped 21% to $211 million.

Sales of Protonix, for severe heartburn, were essentially flat at $409 million. The company said prescription trends show Protonix sales are shifting to more private managed care companies from Medicaid programs, an indication of higher profits ahead for this year. There are greater price discounts for Medicaid than for managed care, the company says.

Sales of the antibiotic Zosyn gained 26% to $229 million for the first quarter. Zosyn is aimed at bacteria that have become resistant to other drugs, and so is the experimental antibiotic Tygacil. This is a new type of antibiotic for which the company sought FDA approval in January. The agency has designated Tygacil a fast-track review candidate.

In other financial matters, CFO Martin describes as "adequate" the reserve set aside for making payments related to the fen-phen diet drug litigation. The reserves were raised during the fourth quarter to a cumulative amount of $21 billion. The reserves cover a 1999 national class-action suit settlement as well as payments to people who file separate suits against the company.

Wyeth's shares were down 15 cents to $43.76.