What comes after 'Menopause'? More of the same.

The songs of Girls Night: The Musical - timeless tunes such as "Girls Just Wanna Have Fun," "Holding Out for a Hero," and the favorite of any bifocal bunch, "I Will Survive" - could play as the life soundtrack for the droves of middle-aged women who have packed the show in recent weeks.

"We can relate," said hairdresser Sharon Hahn, 50, of Runnemede, after she and two dozen of her girlfriends watched the Kimmel Center production about four childhood friends who stayed close through the turbulence of time. "It was awesome."

"It was very inspiring and fun," agreed friend Lois Lampe, an executive assistant who gave her age as "49 and holding."

The friends relished the comic musical revue during their own girls' night out last month, as have thousands of other Philadelphia-area women in the throes of middle age. Girls Night; Respect: A Musical Journey of Women; and Menopause The Musical - all of which feature the anthems of sisterhood and friendship that dominated the airwaves during the '70s and '80s - are proving the rage for gaggles of girlfriends past the big 4-0.

Throughout the two-hour show that Friday, the group - mostly executive assistants who work at Campbell Soup Co. - boogied in the aisles, belted out lyrics from their youths, and laughed till those post-pregnancy bellies they're still trying to work off ached.

"I love the baby boomer songs," said Lampe of Runnemede, who was one of the organizers of the outing. "I definitely would have had all those songs on my iPod - if they had iPods then."

Since Girls Night opened April 20 in the intimate, 215-seat Innovation Studio, it has sold out show after show, said Matthew Wolf, the center's vice president of programming and theatrical presentation.

The vast majority of ticket holders are women in the married-with-grown-kids demographic. "A few guys get dragged along," Wolf said, "and I don't feel particularly good for those guys."

Initially scheduled for five performances a week, the Off-Broadway hit, which closes Sunday, has expanded to eight. "This thing exploded," he said.

At the Society Hill Playhouse, a similar scene is playing out. Respect has been extended four times, most recently through June 27. The musical is closing in on $1 million in ticket sales. "We've sold virtually every seat for the last six weeks," said Philip Roger Roy, one of the producers.

And wherever Menopause - credited as the grandmother of this type of theatrical subject matter - travels, its female fans, hot flashes and all, follow in packs. Recently at the Society Hill Playhouse, where it had a 31/2-year run, it sold 212,000 tickets to a mostly mature crowd, according to Roy.

No theater type would confuse these productions with stage spectaculars such as The Lion King or even Mamma Mia! "I wouldn't necessarily consider these shows high art," Wolf allowed. Theater critics, too, have not always been kind in reviews.

Yet, the shows deliver a certain sort of goods, like a Desperate Housewives with songs.

Carol C. Davis, an associate professor of theater at Franklin & Marshall College, attributes the appeal to the subject matter. Many musicals focus on young love, she noted. But what happens after the honeymoon?

"This isn't a fairy tale," she said. "This is real life. You get old. You get heavy. You go through menopause."

And somehow it's all bearable when set to music. Like the boomers filling the seats, "the women on stage sing their way through life, but with better voices, choreography, and jokes," Davis said.

The actresses, who at times engage the audience in riffs, appear authentic - down to their less-than-perfect bodies. Before the curtain closes, they've become girlfriends to the audience members, "helping each other through the remarkable and unremarkable moments that make up a woman's life."

True, the plot lines are often skeletal - it's really all about the music, after all - but the themes are so completely familiar. Who hasn't gone out for a few drinks with the girls and kvetched about their relationships, about the husbands and kids and bosses?

Girls Night and its ilk "show us the stages of our lives with humor and tenderness, and draw us into a supportive sisterhood," Davis said.

The genre has taken off since the hilarious Menopause hit the stage in 2001. Productions such as Shopping! The Musical; Food Fight!; and Hats! are knockoffs that celebrate the craziness of Everywoman's life.

"It's the quintessential ladies' night out show," Roy, the producer, said. "It's a very accessible genre of theater. It bridges the gap between theater and cabaret entertainment." In fact, plays like these are good at attracting people who are theater novices.

Pat De Sabato, 56, a secretary at Friends' Central School who lives in Wynnewood, wasn't looking for a highbrow experience when she joined a group of 20 female coworkers headed to Respect earlier this year, just a rip-roaring good time. "These old songs, I hadn't heard them in years," she said.

The story of three generations of women and ultimately women's progress - all built around the hits of the day - was "really relevant to a lot of us," Sabato said. "It's fun to look back and reminisce."

Ultimately, popularity comes down to one word: enjoyable - at least for one gender. (Respect, one local theater critic noted, is lacking the same for its smattering of males in the audience.) These comic musicals, which do have their poignant moments, "allow you to laugh at yourself," said Wolf of the Kimmel. "At the core, people want to have fun."

That certainly was the vibe at the show attended by the Campbell Soup crowd. Before the first Girls Night actress even took the stage, emcee Jeremy Sartin, with a Chippendales' bod, was enticing women old enough to be his mother on stage to dirty dance and, for one lucky gal, rip off his shirt. "Anyone celebrating a birthday?" he asked. "Anyone celebrating a divorce?" he added wickedly to roars of laughter.

The par-tay, bachelorette style, was off to a rocking start. Many in the audience imbibed wine from plastic cups, sported light-up tiaras, and draped hot-pink feather boas around their necks. On stage, the jokes - often vulgar in that no-men-around way - came at the expense of husbands, pregnancies, husbands, divorce, and husbands.

"We're lifelong friends," said a giddy Lo Layden, 51, of Westampton, a former Campbell's executive assistant who's director of customer service at Jones Apparel Group.

"We've raised our kids," she said. "This is our turn - a girls' night. We have no shame."