SUN CITY, Ariz. (AP) _ A retirement community might seem an unlikely hotbed for sexual revolution, but such is the power of a little blue pill. Down palm-lined streets where golf, grandkids and gallstones are the usual topics of conversation, the new talk of the town is Viagra, a potent new medicine for male impotence.

Some here call it ``that sex pill.'' Harold Dennis, 61, calls it something close to a miracle.

``I've been impotent since 1986. But last night, I felt good.'' He puts his arm around his wife, Juanita, and flashes a big grin. ``It was very satisfactory.''

In the three weeks Viagra has been available, drugstores nationwide have filled an estimated 150,000 prescriptions. Across America, men have found satisfaction in a way they haven't for years _ and both men and women engaged in the eternal scrimmage of the sexes have found the playing field shifting once again.

There are other treatments for impotence _ vacuum pumps, inflatable implants and drugs that are injected into the penis or plunged down the urethra _ but their disadvantages are obvious.

Viagra is something new: the first pill that makes erections possible. Take the tablet. Wait a half hour. Add a little old-fashioned sexual stimulation. And things begin to happen, perhaps for the first time in a long while.

No wonder doctors can't write prescriptions fast enough.

``It's the biggest thing since the Beatles,'' said Dr. Rafael Wurzel of New Britain General Hospital in Connecticut. He has already made out more than 300 Viagra prescriptions.

``There are about 30 million guys out there'' with erectile dysfunction _ as impotence is called now by most doctors _ ``and hardly any will acknowledge the problem and get help,'' Wurzel said. ``All of a sudden, I see this taboo totally debunked because of Viagra.''

Overnight, patients he'd seen for years for kidney stones, prostate woes, bladder tumors, whatever, began calling him to talk about this other little matter they'd never gotten around to mentioning.

Typical of his patients is Bernard, 58, a retired construction worker who, like many taking the pill, doesn't want to see his name in the newspaper. Cancer and emphysema, plus the side effects of his medicines, have made erections unpredictable for him the past four years, but he's still grinning about the first time he took Viagra.

``I didn't say a word to my partner before,'' he said. ``But afterward, she asked what got into me. This took me back 10 years. It's changed my life. It's given me more self-confidence. I feel good about who I am.''

Doctors generally appear to be prescribing the drug for men like Bernard who have clear physical reasons for their impotence. Among the most common causes are diseases that damage the nerves or interfere with blood flow to the penis. These include high blood pressure, diabetes, clogged arteries, multiple sclerosis and reactions to medications.

``It definitely works, but it won't work for everybody,'' said Dr. William Steers, chairman of urology at the University of Virginia Health Science Center. ``I tell patients that the chance of a home run is 50-50.''

Among those most interested in Viagra are men who have had their cancerous prostate glands removed. The operation often snips nerves essential for erections. Many of these men are still vigorous and healthy, and still interested in sex. But only about 25 percent to 40 percent are likely to be helped by Viagra.

Lon, a retired financial planner in Clovis, Calif., has been impotent since prostate surgery three years ago. The second time he took Viagra, he felt ``a slight beginning of an erection, but nothing to get excited about.'' So he will stick with his inflatable implant, which he says is not as bad as it sounds.

Viagra may not be just for men. Studies are going on to see whether Viagra can rejuvenate women's sex lives, too.

Baltimore hairdresser Laurie Kline took a pill last week and said she had her first orgasm since her hysterectomy five years ago.

``It was like it used to be _ maybe even a little bit better,'' she said.

While specialists are delighted to have something new to offer their patients _ and talk-show hosts are rushing to line up guests _ some observers worry about Viagra's effects beyond the mechanics of erection.

What will it do to couples' relationships? What about the curious who want to see if it revs up normal sexual prowess? How much sex should an aging man expect, anyway? Who will pay for it?

Pfizer Inc., which makes Viagra, stresses that it's not quite a sexual fountain of youth.

``Viagra restores. It doesn't create,'' said spokesman Andy McCormick. ``A 55-year-old man taking Viagra would report a return of desire consistent with a healthy 55-year-old man, not to the level of a 22-year-old.''

Viagra has been tested mostly on men who are clearly impotent, and doctors say there's no reason to believe the drug will do anything for those who get normal erections. But the idea, even without evidence, that this elixir might make erections grow harder, last longer and return sooner clearly intrigues many.

Sun City pharmacist Jim Detwiler couldn't resist trying a pill, even though he says he's fully functional. It made no difference, and it gave him a headache, one of the drug's occasional side effects. (Some other patients report a stuffy nose, flushed skin and indigestion).

Another experimenter was Dr. Karlis Ullis, 54, who has a sports medicine practice in Santa Monica, Calif. He said the pill seemed to give him remarkable sexual vigor, and he sees a future for Viagra as an ``enhancing tool'' for the sexually dissatisfied.

Others wonder what will happen to relationships where men suddenly have more sexual stamina than their aging mates. Will wives worry that husbands will stray? Will they secretly count the pills in the bottle?

``It can bond and unite people, but it can also cause erosions if there is any lack of trust,'' said Dr. Domeena Renshaw, who runs the sex clinic at Chicago's Loyola University.

Cost is another concern. Insurance companies are still sorting out how many pills _ retailing at $8 or more apiece _ they will pay for, if any. For now, about half of prescriptions are being covered.

Some men have already discovered they can halve the price by cutting 100 milligram pills in two. Others say they consider Viagra a bargain, compared with the cost of, say, movies, candlelit dinners, nice clothes and other accoutrements of sex.

Certainly in Sun City, where residents must be 55 or older, the reception is overwhelmingly positive. Impotence becomes more common with advancing age, though accurate figures are scarce.

Dr. Aubrey Chung, a Sun City urologist, said 90 percent of the men he sees ask about the drug.

``I won't say the response is exuberant, but it's very, very good,'' he said. ``A lot patients are relieved that there's something other than invasive techniques available.''

Not every older gentleman wants to restart a dormant sex life. More than one Sun City retiree said he was more likely to spend money on Pfizer stock than on the pills.

``I haven't had sex in 15 years, and I don't miss it,'' said Alvin Larned, 71. ``My wife and I had our fun, but now it's over. I play shuffleboard, bocce. There are plenty of other things to do.''

Sure, but none quite as enjoyable as sex, said Harold Dennis, a retired carpenter. He's tired of his years of involuntary abstinence.

``I've tried everything they said to try,'' he said. ``I've been to specialists, I've been to urologists. I've had the needle in the penis. I've had the testosterone. I had an implant put in, and then taken out after five months when it didn't work right. This Viagra is the best thing we've tried.''

If his health insurer balks at paying for the pills, he'll switch companies.

``I'd rather have my sex life than good health,'' Dennis said. ``In the hereafter, I'm not going to have sex. As long as I'm alive, I want it, and this pill is the yellow brick road.''

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EDITOR'S NOTE _ David Foster is the AP's Northwest regional reporter, based in Olympia, Wash. Daniel Q. Haney is medical editor for the AP. AP Business Writer John Hendren also contributed to this report.