A Potent Pill For The Endangered? / Viagra might save species
hunted as aphrodisiacs of choice
By Robert Cooke. STAFF WRITER
Newsday 10/22/98
IT'S ALL SPECULATION so far, but some friends of wildlife hope the
ego-enhancing drug Viagra may have an unintended beneficial side effect:
reducing the lethal pressure on endangered species.
Though Viagra wasn't designed to have environmental impact, some
observers suspect, or hope, that Viagra's power to correct impotence may
soon reduce demand for various animal organs. Oddities such as
rhinoceros horns, bear gall bladders and tiger penises are said to be
processed and peddled widely throughout Asia as aphrodisiacs.
This folk-medicine industry is known to supply much of the incentive for poachers who are slaughtering animals in places as widely separated as Africa, North America and Asia.
Now, according to researcher Frank von Hippel, "in Viagra we now
have the potential to eliminate the demand for animal potency
products." In fact, he said, "the cost of Viagra is trivial compared to that of rhino horn or bear gall bladder. And Viagra's effectiveness is demonstrated rather than hoped for."
A physicist at Columbia University's Habitat 2 lab in Arizona, von
Hippel noted, "These animal parts - known in East Asia as pu foods -
are reputed to endow a man with the potency of the animal itself, or
with the potency implied by the shape of the appendage."
In a letter to Science magazine, von Hippel said that "efforts to
conserve these endangered species . . . have largely failed because the market forces driving the poaching remain in place. Indeed, the demand for these products has intensified because the Chinese economy and the number of wealthy Asian consumers have grown in recent years."
Reducing such demand, he said, "may be a more effective conservation measure and a less costly alternative to captive breeding, artificial insemination and embryo transfer" for animals that "are being hunted to extinction." That may be wishful thinking, however. Some observers see little chance that Viagra will do much good for endangered wildlife, because some animal parts, such as rhinoceros horn, are used for things other than sex enhancement. The tough, fibrous material in rhino horns, for example, is coveted by Yemenis as handles for exotic daggers.
Also, a group that routinely monitors the worldwide trade in illicit animal parts, the Environmental News Service, sees little chance that even wide use of Viagra will reduce the demand for animal organs.
The answer, of course, will lie in experience. And so far, too
little Viagra has reached the Far East to make much difference. The
drug's manufacturer, Pfizer, reports more than 30 million pills have
been prescribed, and as of June 30 about $411 million worth of Viagra
had been sold. But those numbers do not mean much of a supply has yet
gone to Asia, where aphrodisiacs are so popular.
So far, use of Viagra has been officially approved in about 15
nations, but only in Thailand in the Far East. And supplies just
recently began entering Germany.
Predictably, already "there is a black market" for the drug in Asia, "including Korea and Japan, but not much yet in China," said Andrew McCormick, a Pfizer spokesman. Also, urban rumors about truckloads of Viagra being hijacked here in the United States are not true, he said.
According to recent news from Korea in U.S. News and World Report,
customs officials in South Korea are intercepting bottles of Viagra,
which now sell for about $700 for 30 pills. Korean-American tourists are said to be bringing in pills disguised as vitamins. In one week a
reported 40 Viagra smugglers were discovered.
McCormick said most Asian countries will probably join Thailand in approving Viagra by the end of the year. China, massive China, is not on that list, however, but may follow within a year or so.
No studies have yet been done concerning whether the advent of
Viagra might redound to the benefit of tigers, bears, rhinoceroses or
other hunted species, McCormick said. But "in the East, traditional
medicines and herbs are pretty well regarded. They are commonly used,
and how Viagra will impact that is anybody's guess."
If the sales experience with Viagra in the United States and Europe is any guide, however, it's likely the new impotence-erasing pills will be an instant hit all over the place, regardless of what's going on in the animal-parts business.
Even now, without Viagra yet available throughout Asia, one of the
drug's discoverers, Pfizer chemist Nick Terrett, said, "It's clear we
underestimated the size of the market and the number of men" who'd like to get the drug. Other drug companies, such as Eli Lilly, are hurrying to get their own impotence-erasing medicines approved and marketed.
Despite the huge success of Viagra, Terrett is somewhat miffed by
the inevitable Viagra jokes that have emerged. "We don't really like
people taking it lightly," he said. "We understand that erectile
dysfunction [impotence] is a fairly serious disorder. There is a lot of trivialization" of the topic. "I feel it's inappropriate to make jokes" about the drug and impotence, he said.
Also, Terrett and his colleagues at Pfizer's central research
facility in Kent, England, resent widespread reports that Viagra was
found by accident.
"The story that the media have promoted is that the discovery is
serendipitous," he lamented. But "fortune favors the prepared mind" that is alert to exploit new findings, Terrett said. The result is that "we have a high-quality drug, and erectile dysfunction was the home where that drug would have the most impact. This just reflects an investment in basic research."
Nonetheless, the research was not originally being done with
impotence in mind.
"We started the program in 1985, looking for a class of chemicals
with the potential for treating cardiovascular disease," Terrett said.
"We started out looking at hypertension, but that soon evolved into
looking at angina," the syndrome that involves episodes of chest pain
caused by poor blood flow to the heart muscle.
"In the discovery process, we made about 1,500 chemical compounds,
and we tested and screened them for over four years," he said. "And in
1989 we found the chemical we now know as Viagra. We designed it; we
synthesized it from scratch."
Terrett explained, "We were looking for things that were potent and have a high affinity" for interacting with an enzyme known as PDE5, or phosphodiesterase. "This was pretty original work. Very few compounds of this sort are known; all the others are very weakly active."
The goal was to find chemicals that inhibit the enzymatic action of PDE5. The enzyme's normal task is to break down a substance called
cyclic GMP, a so-called messenger molecule that causes dilation of blood vessels, prevents blood platelets from clumping and is somehow involved in facilitating penile erections.
Once a promising compound, Viagra, had been identified and tested,
"we went into clinical trials in the United Kingdom, to treat angina,
looking at safety and toleration" of the drug," he explained. "The idea was to find a compound to dilate blood vessels and prevent thrombus [blockage] formation." Then, in about 1992, he said, three things happened.
"First, we had results from Phase II trials in angina patients"
where it was being tested for efficacy. "It was less efficacious than
we'd hoped, and that was disappointing," Terrett said. But "at the same time, we discovered that in some of the late-stage Phase I studies, in
normal men, we began getting erections reported as a side effect."
Second, "there was a lot of evidence in the literature saying the
mechanisms by which our drug worked" involved interactions with nitric
oxide. "We knew our drug would amplify the effect of nitric oxide,"
which "is produced in blood vessels and dilates them."
And third, it was recognized that "nitric oxide is a mediator oferection."
"So these three came together: There was anecdoctal evidence of
erections" in the drug trial, reports in the literature about nitric
oxide's effects on blood vessels, and evidence that erectile function is related to nitric oxide.
But the discovery posed a dilemma for Pfizer. Within the company,
Terrett said, "there was a lot of discussion about whether to go ahead
and study it [Viagra] for erectile dysfunction. Pfizer had no experience in this area, and there was no precedence for large clinical trials."
Nonetheless, within 18 months "we had designed our first Phase II
clinical trial" to see if Viagra could really have impact on impotence, Terrett said. "It was found that 10 out of 12 patients reported improved function," compared to only two of the men who were given placebos.
As for Viagra's side effects, Terrett said there were no surprises. "We knew from the Phase I study that they are generally mild and transient. They include headache, indigestion and visual disturbances - a greater senstivity to light, or blue coloration. We know why it happens. It's reversible, and it leaves no permanent damage. It is not dangerous."
The changes in vision occur, because Viagra affects another enzyme, a phosphodiesterase, found in the retina of the eye.
Even larger trials were successful, he added, noting that "in one of the late clinical trials of 225 patients, less than 4 percent withdrew due to side effects."
In fact, he added, "there have been no surprises" in terms of side
effects, since the results so far "reflect precisely what was observed
in the clinical trials."
Complications that were not negligible, however, were the deaths of a small number of men, mostly men who used Viagra while also taking
nitrate-based drugs for cardiovascular disease. These deaths have
occurred despite clear warnings included with Viagra telling heart
patients not to use the drug.
"The important thing is that all patients who take Viagra should
have erectile dysfunction diagnosed by a doctor," Terrett said. "The
deaths that have occurred so far are either due to taking nitrates,
which are contraindicated, or are due to the physical activity of sexual intercourse."
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