Blindness noted in men using impotence drugs
Levitra is sold in the United States by GlaxoSmithKline PLC and Schering-Plough Corp. and overseas by Bayer AG.
Viagra was approved by the government in 1998. It may aid in the treatment of enlarged hearts that can result from high blood pressure, tests on animals indicate.
Levitra was approved in August 2003, and Cialis in November of that year.
There have been no reports connecting Levitra to blindness, said Michael Fleming, a spokesman for GlaxoSmithKline PLC. “We are confident about the safety of our product,” said Fleming.
Viagra, approved to treat erectile dysfunction, should not be used by men with heart conditions whose doctors have warned them not to have sex. Also, patients taking drugs that contain nitrates have been warned not to take Viagra because of sudden, unsafe drops in blood pressure.
The drug’s label also warns of erections lasting longer than four hours, painful erections lasting longer than six hours, headache, flushed skin and vision problems.
Pfizer Inc. said in its most recent quarterly filing with the Securities and Exchange Commission that sales of the drug rose 5 percent — to $438 million in the first quarter of the year. Pfizer also said at the time that Viagra had a 68 percent worldwide market share.
Viagra sales have been under pressure from new competitors Cialis and Levitra, with revenue sinking 11 percent last year to $1.68 billion from $1.88 billion.
Doctors and patients have become increasingly wary of the downsides of prescription drugs after Merck & Co. yanked its pain reliever Vioxx from the market last year because of its potentially lethal side effects.
Merck potentially faces thousands of lawsuits over Vioxx and analysts have estimated its liability may reach $18 billion.
Pfizer was asked to remove its pain reliever Bextra from the market because of its side effects and sales of its other arthritis drug Celebrex are falling. Vioxx, Celebrex and Bextra all fall into a category of drugs known as Cox-2 inhibitors.
Industry critics have been demanding that drug companies conduct more post-marketing studies in order to do a better job of discovering side effects once drugs hit the market.
For more than two decades, Americans have mostly pressed for quicker approval of what they hope can be lifesaving drugs for such diseases as AIDS and cancer. But many now are wondering if medicines — a $200 billion industry annually — are coming out too fast and doing too much harm.
Viagra also is at the center of controversy over Medicaid’s payment for prescriptions of the drug to convicted sex offenders in New York and other states.