The retinal side effects of Viagra according to the Barons article are now up to 10% from the previously published 2% ( I think ) in Phase III Viagra trials.
This is due to people's increasing use of the higher approved dose of 100 mg. At this higher dose, even though Viagra is a selective PDE5 inhibitor,it now becomes non-selective, like every other known phosphodiesterase inhibitor, and starts inhibiting PDE6 in the retina thus causing the blue vision .
In the long term this continued stimulation of the retina can cause premature retinal degeneration and blindness. This may cause a restriction in it's wide spread use even more than the deaths reported so far, although those too are worrisome.
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interactive.wsj.com
By Andrew Barry, Barons, July 6, 1998, page MW5
IS VIAGRA STARTING TO FADE?
Following a steady decline in new prescriptions during the past month, there's some concern on Wall Street that Pfizer's widely hyped impotence drug may not prove to be a multibillion-dollar blockbuster. The worries have depressed Pfizer's stock, which has become prisoner to developments surrounding Viagra in recent months.
Pfizer fell 4 7/16 to 107 1/2 last week, and is down from a record 121 3/4 at the time of the drug's launch in late April.
New prescriptions for Viagra peaked at over 278,000 in the week ended May 18 but fell to 151,000 in the week ended June 19, the most recent reporting period, according to IMS America, the Nielsen of the drug business. The weekly "script" data are still extraordinarily high for a new pharmaceutical, and refill prescriptions for Viagra continue to increase.
But given the enormous expectations for the drug and the runup in Pfizer's stock this year, any indication of slowing momentum for Viagra causes some nervousness among investors. Pfizer is up 44% in 1998, 78% in the past year and commands the highest multiple in the drug group, trading at over 50 times projected 1998 profits.
"A lot of people are saying Viagra will do $1 billion in sales this year and eventually hit $5-$10 billion annually. I don't think that will happen," says James Flynn, drug analyst at Furman Selz. Flynn, who recently downgraded Pfizer to Hold from Buy, sees Viagra ringing up $2 billion in annual sales in five years, an impressive level but below the most optimistic projections. Flynn says the recent prescription data show Viagra's U.S. sales running at an annual rate of $700 million.
"If you look at lifestyle drugs, they typically peak about three months after they're launched," he says. The big question regarding Viagra is whether it's just another "lifestyle" drug like diet pills or baldness remedies and thus lacks staying power. Or is Viagra, which already has had the strongest debut of any drug in history, on its way to becoming the biggest-selling prescription drug in history?
Flynn argues that most men who really wanted the product already have it. "Pfizer has probably seen 100% penetration of the easy-to-reach market," he adds. The challenge now for the company will be enticing the millions who might benefit from Viagra but haven't shown an interest in trying it yet. "You've got men who are embarrassed, don't care, or would care more if the drug weren't so expensive." Viagra costs about $10 a dose and isn't covered by many insurance plans.
So far, Pfizer has done a good job addressing safety concerns about the drug, including the deaths of men taking Viagra. But there hasn't been any long-term testing of Viagra. One concern is whether the drug begins to lose its effectiveness over time. Pfizer says there's no evidence of this.
However, Flynn points out that Viagra users are increasingly favoring higher-dose pills. "This suggests people aren't getting the desired effect from the lower dosage," he reasons. Viagra is available in dosages of 25, 50 and 100 milligrams. The 100-milligram pills have risen to 22% of prescriptions from 8% initially. One problem with the stronger pills is that they cause a higher incidence of visual color disturbances, or bluish vision, according to Neil Sweig, an analyst at Southeast Research Partners.
Pfizer downplays the blue-vision side effect, which occurs in about 10% of men taking the 100-milligram pills, saying it's "confident" there are no long-term effects on the vision of those taking the proper dosage. But Sweig, citing the views of many eye doctors, wrote recently that the blue-vision issue could be "serious." He said blue vision appears to be a "unique" side effect of Viagra that isn't present with any disease or other drug and that "some event" is occurring in the retina to trigger the problem. It's too early, he wrote, to determine whether Viagra has no long-term adverse effect on the eyes.
In downgrading Pfizer, Flynn also cited the company's surprise setback recently involving Zeldox, a schizophrenia drug, which got a "non-approval" letter from the Food and Drug Administration. The Street was hoping that Zeldox could become a $500 million product, but now it's unclear whether it will ever come to market.
Flynn also points out that Pfizer has reaped enormous benefits from co-marketing Warner-Lambert's blockbuster cholesterol drug, Lipitor, which could generate $2 billion in sales this year. But the downside for Pfizer is that it must reciprocate and give Warner-Lambert co-marketing rights to one of its new drugs. Flynn says Pfizer might have to give Warner the co-marketing rights to two drugs to make up for its Lipitor windfall, diminishing the value of its own admittedly strong pipeline. Neither Pfizer nor Warner have revealed much about the Lipitor agreement.
While Pfizer fell last week, Warner-Lambert hit a new record, rising 6 1/8 to 73 1/8 . Warner benefited from a recommendation by an analyst at Donaldson Lufkin & Jenrette, solid sales of its diabetes drug Rezulin, and optimism about its marketing agreement with Pfizer. Warner, which has doubled since the Rezulin safety scare last December, now sports a multiple that's nearly as high as Pfizer's. Warner trades at almost 50 times projected 1998 profits and at 40 times estimated 1999 earnings of $1.82.
Christina Heuer, Smith Barney's drug analyst, says investors are overreacting to the Viagra prescription data. "People are missing the big picture. Pfizer has a brilliant outlook and phenomenal earnings momentum." A Viagra bull, Heuer estimates that sales of the drug will hit $2 billion next year and $5 billion worldwide in 2002. Pfizer, she says, will be powered by Viagra, Lipitor and Celebra, the first of a new class of drugs being developed to treat arthritis pain.
Heuer, a long-time Pfizer fan, sees the company earning $2.15 a share this year, $2.70 in 1999. Her price target for the stock is $150 by the end of 1999.
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