Pfizer hopes other drugs will match the success of Lipitor and Viagra

The end of sales exclusivity on certain drugs hit Pfizer's second-quarter performance, with profits falling to $2.4bn (�1.29bn) from $3.4bn last year.

But Pfizer said its results were "quite encouraging", citing strong sales of anti-cholesterol drug Lipitor.

Pfizer is selling its consumer health arm to Johnson & Johnson to focus on research and production of new drugs.

'Meeting challenges'

The US firm - also the manufacturer of anti-impotence drug Viagra - said it would use some of the proceeds of the $16.6bn deal to boost its product pipeline through "targeted acquisitions".

Expiring patents are expected to reduce Pfizer's revenues from drug sales by about a third between 2004 and 2008.

Many companies could not survive such a profound loss of revenue Hank McKinnell, Pfizer chief executive Check Pfizer shares

The firm has also had to contend with the loss of painkiller Bextra, which it voluntarily withdrew from sale in 2005 amid health concerns.

But Pfizer said its business was strong enough to withstand these developments, as well as the increasingly fierce competition from generic producers of rival medicines.

"Many companies could not survive such a profound loss of revenue," said Hank McKinnell, Pfizer's chairman and chief executive.

"Our latest results show that we are consistently and successfully meeting the challenges we face - in particular, offsetting loss of exclusivity for several of our products with solid growth from in-line and new products."

Pfizer hailed a strong performance from cholesterol reduction drug Lipitor, whose global sales rose 9% to $3.1bn on the back of increased demand from Asia in particular.

Eight other leading drugs enjoyed double-digit growth in sales.

But Pfizer's overall sales rose a more modest 2.5% to $11.7bn.