More than US$31 billion was on Friday knocked off the value of Pfizer, the world's largest pharmaceutical company and maker of Viagra, after doubts surfaced over the safety of one of its key drugs.
The revelation comes only weeks after rival Merck decided to withdraw its painkiller Vioxx, from the same family of drugs, because of similar side-effects fears.
News that one of Pfizer's main drugs, Celebrex, used to combat arthritis, could cause heart problems emerged on a dark day for the world's drug giants. British pharmaceuticals group AstraZeneca yesterday suffered its third setback in two months as a clinical trial showed its lung cancer drug Iressa failed to help patients live longer. The news saw the value of the company, one of the UK's largest corporations, drop ?2.8 billion in value yesterday.
There had been hopes that the drug offered a breakthrough in cancer treatment, but a study of just under 1,700 patients showed that it appeared to have no significant life-prolonging effects.
The blow follows recent news that AstraZeneca's drug, Exanta, used to treat strokes, had been blocked by the US regulatory authority.
Its anti-cholesterol drug, Crestor, has also faced stiff criticism from US officials. These setbacks have called into the question the future of AstraZeneca's chief executive, Sir Tom McKillop.
In New York Pfizer's shares plummeted after it said trials of Celebrex as a treatment for cancer rather than arthritis showed it more than doubled the risk of heart problems.
Celebrex comes from the family of drugs known as Cox-2 inhibitors which includes Vioxx. Cox-2 is a protein which is believed to cause inflammation of the joints.
Both Celebrex and Vioxx are anti-inflammatories and were launched in the US market five years ago backed by mammoth advertising campaigns.
Celebrex is one of Pfizer's biggest selling drugs, accounting for sales of US$1.9 billion last year. The US group also has a second newer drug in a similar area called Bextra which was worth US$687 million in sales last year.