Two giant American drug companies - Pfizer and Warner-Lambert - have announced they're merging to create the second biggest pharmaceutical group in the world.

The deal is worth some ninety billion dollars and their products include the anti-impotence drug, Viagra.

Pfizer will be the main partner, with its chief executive taking control of the new group.

The BBC business correspondent says the cost of developing new drugs is so high, both companies believe that combining their budgets will give them a crucial advantage and he says many more mergers are likely in the industry.

From the newsroom of the BBC World Service