Wyeth posted a first-quarter profit increase of 4% on Friday, as sales rose 6% on the back of contributions from its arthritis drug Enbrel, antidepressant Effexor and gastrointestinal drug Protonix.

Net income was $1.12 billion, ahead of analyst expectations, on revenues of $4.8 billion for the first quarter. Wyeth said the results were buoyed by a restructuring that reduced costs and boosted sales force productivity, and the figures spurred a 1.6% rise in the company’s share price by the close of trading, ending at $47.50.

Sales of Effexor (venlafaxine), Wyeth’s flagship product, rose a healthy 9% to $945 million, shrugging off a general downturn in the market for antidepressants that has followed concerns over an increased risk of suicidal thoughts and behaviour in children and adolescents.

There’s a dark spot on the horizon for Effexor, however, as it will soon be facing generic competition in the important US market when Teva Pharmaceutical Industries rolls out a copycat version of the drug later this year. Wyeth still maintains that sales of Effexor will maintain ‘mid-single-digit’ growth through the remainder of 2006.

Paediatric vaccine Prevnar had another good quarter, growing 10% to $432 million and providing additional evidence of the rewards that can be accrued by operating in the resurgent vaccines sector, while Protonix (pantoprazole), also under the threat of generic competition, leaped 18% to $482 million.

Teva said on Friday said that it has received tentative FDA approval to market a generic, delayed-release version of pantoprazole, depending on the outcome of ongoing patent litigation between the two companies.

Sales of Enbrel (etanercept), a drug for rheumatoid arthritis marketed by Wyeth outside North America, surged 42% to $335 million. And also putting in a recovery was hormone replacement therapy Premarin (conjugated oestrogens), which advanced 26% to $266 million despite the safety concerns linked to HRT of late.

Meanwhile, Wyeth said it has agreed to settle 50,000 of the 62,000 suits filed by users of the diet drug combination, known as fen-phen, that are not part of a national class-action settlement. Wyeth has put aside more than $21 billion to cover the costs of settling the cases, which involve plaintiffs who claim injury after taking the drugs to lose weight. The combination has been linked to heart valve problems.