Since Ms. B. entered her mid-40s, she says, sex has been more about smoke and mirrors than thunder and lightning. She is rarely if ever interested enough to initiate it with her partner of 10 years, and she does not reach climax during the act.

She wishes it were otherwise. “Sex just isn’t a priority anymore,” said Ms. B., 45, a professor in New York who spoke on the condition that only her last initial be used. “Still, it would be nice not to feel sexually dead.”

Ms. B.’s plight is far from unique, and now the marketplace is starting to respond. In the absence of a government-approved female counterpart to men’s potency drugs like Viagra, Cialis and Levitra, many women are turning to over-the-counter products, including lubricants, arousal gels, massage oils, nutritional and herbal supplements, and vibrators. Drugstore chains are now selling these products right next to the bandages and heating pads.

K-Y Intense, a female arousal gel that claims to heighten clitoral sensitivity, is sold in Walmart, Walgreen and Rite Aid. Sensuva’s ON, an arousal oil, can be found in 640 GNC stores nationwide. Intimina by LELO, an “intimate lifestyle line” that manufactures personal massagers, apparel and “intimate cosmetics,” is sold at Pharmaca Integrative pharmacies. And Zestra Essential Arousal Oil is now sold in 1,800 Walmarts, up from 880 in 2010.

“The average woman in a committed relationship is having sex once a week,” said Rachel Braun Scherl, president of Semprae Laboratories, the manufacturer of Zestra, which recently signed Kris Kardashian Jenner as a spokeswoman. “Our idea is not to get them to have more sex — it’s that if they’re having sex they should enjoy it.”

How well these products work is unclear. The industry is unregulated, and there have been hardly any clinical trials. In a randomized study reported in 2010 in The Journal of Marital and Family Therapy, women using Zestra oil reported significantly more desire, arousal and satisfaction than those given a placebo. K-Y claims that 70 percent of women in a survey agreed that its Intense gel increased arousal, orgasmic intensity, satisfaction and pleasure, but the research has not been published in a medical journal.

Erin Drought, a 28-year-old information technology consultant in Edmonton, Alberta, who says her sex drive evaporated after she began taking medicine for bipolar disorder, stumbled on Zestra in a grocery store and tried it on a whim. She did not tell her husband because “I didn’t want to get his hopes up.” But for whatever reason, she said, it worked.

“It was like a light switch,” she said. “It was almost like the time I got my new pair of glasses and I could finally see things from far away. It was like, ‘Wow, this is what it feels like to see.’ ”

Many of the arousal products use “peppermint oil or some variation; the idea is to make you tingly,” said Bat Sheva Marcus, clinical director of the Medical Center for Female Sexuality in Manhattan and Purchase, N.Y. “Some people find it burns, some find it really arousing, or nothing.”

A more difficult question is how to define “sexual enhancement” in the first place. For men, after all, the problem tends to be self-evident; for women the questions are more complicated.

“Do they not want to have sex at all? Is there a decrease in sexual desire? Do they have an orgasm? You have to separate it,” said Dr. Cheryl L. Perlis, a gynecologist in Lake Bluff, Ill. “Some people can’t physically have an orgasm at any age. There are a lot of different definitions.”

Female sexual dysfunction remains a controversial topic, even as it becomes an official diagnosis (to be called female sexual interest/arousal disorder) in the DSM-V, the new edition of the psychiatric diagnostic manual, due in 2013. An often cited statistic, from a report in The Journal of the American Medical Association in 1999, is that 43 percent of women ages 18 to 59 experience some form of sexual dysfunction, including lack of desire, arousal or orgasm; or pain during intercourse.

But while that figure is widely used by doctors and in marketing campaigns, Liz Canner, the director of the 2009 documentary “Orgasm Inc.,” notes that it was taken from a sociology survey conducted in the early 1990s to find out what people’s sex lives were like. “It was never meant to measure the number of women with a disease,” she said.

Leonore Tiefer, a sex therapist who is a clinical associate professor of psychiatry at New York University School of Medicine, argued in a 2006 article in PLoS Medicine that female sexual dysfunction was a cultural construct, a “textbook case of disease-mongering by the pharmaceutical industry and by other agents of medicalization,” including health care professionals and journalists.

Dr. Marcus, of the Medical Center for Female Sexuality, disagrees. “F.S.D. is a real problem,” she said. “To say that women are complaining about their sex lives because pharmaceutical companies told them to is really insulting to women.” (She said she had no financial ties to any of the companies.)

And Dr. Michael L. Krychman, a gynecologist in Newport Beach, Calif., who specializes in sexual medicine, said: “These sexual complaints are real; they’re not imagined. Women are suffering in silence, and they’re looking for solutions.”

He added that one reason men often fail to renew their prescriptions for Viagra is that they are not addressing their partners’ sexual needs. “Some women say, ‘An orgasm used to be thunder and lightning, and now it’s only the pitter-patter of rain — and I’m waiting outside with my umbrella, and waiting and waiting and waiting,’ ” he said. (Dr. Krychman has advised companies like Semprae Labs and LELO, and sits on drug company boards.)

Still, the proliferation of these products — and their emphasis on fixing a problem that is extremely hard to define — leaves some people worrying that women will start focusing on so-called trouble spots and putting pressure on themselves to perform.

“What I don’t like is that we’re exploiting that desire by selling women products that may not be the best thing for our bodies and may not work,” said Tammy Nelson, a sex and relationship therapist in Connecticut and the author of “Getting the Sex You Want” (Quiver, 2008).

This month, LELO plans to offer 24 new products, including nipple masks, nipple spray, and “anti-aging and cellular renewal cream” for the vagina, clitoris and nipples and the skin around the inner thighs. There have been no medical studies suggesting that these are necessary. But Donna Faro, director of sales and marketing for LELO, said, “We have studied the skin, and we understand what’s lacking in areas of a woman as she ages.”

For Dr. Marcus, such claims are almost beside the point. About the broad array of female sexual enhancement products, she said, “For some people they work, for some people they don’t — it’s like anything to do with sex.” And she added:

“Do they work for serious issues? No. But do they work to make your sex life more fun? Maybe. There’s certainly no harm in trying.”