When a Food and Drug Administration panel last month recommended against approving a proposed treatment for low libido in women from a German pharmaceutical company, it was billed as the latest setback for a 'female Viagra.'

But contrary to popular belief, erectile-dysfunction drugs like Viagra don't fix male libido problems, either. By enhancing blood flow, ED medications may help create or maintain an erection, but they don't provide the desire for one in the first place. They don't deliver what Boston urologist Abraham Morgentaler calls 'the hunger for sex -- that grrrr.'

Libido technically means the urge, instinct or psychic energy to have sex, and everything from falling hormones and child rearing to rising responsibilities and job loss can dampen it. Experts are pondering the distinction, in both men and women, between 'desire' and 'arousal.'

'The relationship between what happens in the genitals and how people feel about it is more complex than we realized,' says Erick Janssen, researchscientist at the Kinsey Institute for Research in Sex, Gender and Reproduction at Indiana University, in Bloomington. 'You can, in principle, feel desire without necessarily showing any signs of physical arousal, and you can have signs of physical arousal without feeling desire.' Yet, proposed changes for the next edition of the Diagnostic and Statistical Manual of Mental Disorders, a psychiatric handbook, would combine a lack of interest in sex in women ('hypoactive sexual desire disorder') and difficulty being aroused into a single disorder. A similar change may be proposed for men.

As for sexualfrequency, many people simply want to know: What's normal? But that's a trick question. Studies have found that American married couples on average have sex about once a week, but there's a vast range, depending in part on age. As many as 15% of married couples haven't had sex in the past six months to a year, says Denise Donnelly, a sociologist at Georgia State University. Wide variation exists among same-sex couples too.

'There are all different kinds of normal -- the key thing is, what's normal for you?' says Mary Jane Minkin, clinical professor of obstetrics and gynecology at Yale School of Medicine. 'There's really only a problem when there's an asymmetry' between you and your partner, she contends. 'If it's peaceful coexistence, it's fine.'

That's a big 'if,' though. An oft-quoted University of Chicago study from 1992 found that some 15% of men -- and 30% of women -- nationally reported a lack of interest in sex for at least some part of the previous year. In a relationship, when one partner's interest starts out higher or wanes faster than the other's, hard feelings can ensue.

The first step -- and often the hardest -- is honest communication. 'Low libido can be a proxy for all sorts of other things, from 'I'm really angry at you and can't tell you' to 'I took care of the kids all day and I'm exhausted,' ' Dr. Donnelly says.

'If the woman says, 'I love you, but I really don't have any libido,' look for medical issues,' Dr. Minkin says. The same applies to men.

Heart disease, high blood pressure and other health problems can put the kibosh on desire. Medications from antihistamines to beta-blockers also can lower libido. Reduced sex drive is a common side effect of selective serotonin reuptake inhibitors, such as Prozac.

Getting older can dampen sexualappetite. In men and women, hormone levels drop naturally with age, often taking desire with them. In menopausal and perimenopausal women, falling estrogen levels can lead to vaginal dryness and make intercoursepainful, Dr. Minkin says. In such cases, she recommends a topical lubricant. 'Only a crazy person would have sex if it hurts,' she says. If that doesn't work, she may suggest estrogen or testosterone replacement or both.

And many women aren't aware that some birth control pills -- especially those that help reduce acne by lowering testosterone levels -- also can lower libido.

Low libido in men is complicated too. Many men don't separate the desire for a sex life in the abstract from the desire for sex. 'A man may say, 'I want to have sex very much. I've got a beautiful wife. It's important to me.' That's not what libido is,' says Dr. Morgentaler, director of Men's Health Boston, which specializes in sexual and reproductive problems.

Low testosterone is the No. 1 killer of male libido, he maintains, and as many as a third of men age 45 and older have testosterone levels low enough to diminish desire and interfere with erections.

The real libido killer may be the partners' relationship. 'Women sometimes assume they're no longer attractive, or they've gained weight. But that's usually not it,' says Dr. Morgentaler. 'If there was one thing I could say to every femalepartner of the guys I see in my office, it's this: 'Let the man be the man in at least one area of the relationship, instead of always telling him what he's doing wrong.' ' He adds, 'Men need to feel powerful to feel sexy.'

'Exactly the same thing happens with women whose husbands make every decision,' counters Dr. Donnelly. 'They're thinking, 'Hmm, sex is the one thing I can withhold.''

Carole Goldberg, a certified New Haven, Conn., sex therapist says the most common nonmedical problems she sees are stress, fatigue and lack of time. 'I have couples who get out their day planners and say, 'How about Saturday at 6 o'clock?''

One partner may simply want sex more often than the other. The one who wants sex less usually has the upper hand, notes Dr. Donnelly. She has studied 'involuntarily celibate' marriages and thinks they are more common than generally believed. Many couples she studied said, 'I love my partner. This is a perfect relationship in every way except sex.' But unevensexualappetites often make for unstable relationships. 'One partner is always wondering what's wrong with them, and that makes them very ripe for the picking.,' she says.

But maybe the problem is just the cat or the lumpy mattress. Conditions, and partners, need not be perfect, experts stress. 'People can have absolutely nothing in life and still have a great sexualrelationship,' Dr. Morgentaler says. 'The key is being really generous to your partner.'

Melinda Beck

• administration [əd,minis´treiʃən] n.管理(事务等)；经营 (初中英语单词)
• treatment [´tri:tmənt] n.待遇；对待；治疗 (初中英语单词)
• contrary [´kɔntrəri] a.相反的 n.相反 (初中英语单词)
• belief [bi´li:f] n.相信；信仰，信条 (初中英语单词)
• maintain [mein´tein] vt.维持；保持；继续 (初中英语单词)
• hunger [´hʌŋgə] n.饥饿；渴望 (初中英语单词)
• instinct [´instiŋkt] n.本能；直觉；天资 (初中英语单词)
• energy [´enədʒi] n.活力，精力；能力 (初中英语单词)
• distinction [di´stiŋkʃən] n.差别；特征；卓越 (初中英语单词)
• complex [´kɔmpleks] a.复杂的 n.综合企业 (初中英语单词)
• research [ri´sə:tʃ] n.&vi.调查；探究；研究 (初中英语单词)
• institute [´institju:t] n.学院 vt.建立；设置 (初中英语单词)
• physical [´fizikəl] a.物质的；有形的 (初中英语单词)
• mental [´mentl] a.精神的；心理的 (初中英语单词)
• combine [kəm´bain] v.(使)结合；联合企业 (初中英语单词)
• normal [´nɔ:məl] a.正规的 n.正常状态 (初中英语单词)
• partner [´pɑ:tnə] n.伙伴 v.同....合作 (初中英语单词)
• peaceful [´pi:sfəl] a.和平的；平静的 (初中英语单词)
• previous [´pri:viəs] a.先，前，以前的 (初中英语单词)
• communication [kə,mju:ni´keiʃən] n.通信；通讯联系 (初中英语单词)
• medical [´medikəl] a.医学的；医疗的 (初中英语单词)
• pressure [´preʃə] n.压榨 vt.对...施压力 (初中英语单词)
• appetite [´æpitait] n.欲望；食欲 (初中英语单词)
• complicated [´kɔmplikeitid] a.结构复杂的；难懂的 (初中英语单词)
• director [di´rektə] n.指导者；....长；导演 (初中英语单词)
• diminish [di´miniʃ] v.减小，缩小 (初中英语单词)
• interfere [,intə´fiə] vi.干涉；妨碍；打扰 (初中英语单词)
• attractive [ə´træktiv] a.有吸引力；诱人的 (初中英语单词)
• female [´fi:meil] a.女(性)的 n.女人 (初中英语单词)
• stress [stres] n.强调；压力 vt.强调 (初中英语单词)
• absolutely [´æbsəlu:tli] ad.绝对地；确实 (初中英语单词)
• generous [´dʒenərəs] a.慷慨的；丰盛的 (初中英语单词)
• relationship [ri´leiʃənʃip] n.关系；联系；亲属关系 (高中英语单词)
• scientist [´saiəntist] n.(自然)科学家 (高中英语单词)
• indiana [,indi´ænə] n.印第安纳(州) (高中英语单词)
• necessarily [´nesisərili] ad.必定，必然地 (高中英语单词)
• edition [i´diʃən] n.版本；很相似的 (高中英语单词)
• disorder [dis´ɔ:də] n.杂乱 vt.扰乱 (高中英语单词)
• georgia [´dʒɔ:dʒjə] n.乔治亚 (高中英语单词)
• variation [,veəri´eiʃən] n.变化；变动 (高中英语单词)
• painful [´peinfəl] a.痛(苦)的；费力的 (高中英语单词)
• fatigue [fə´ti:g] n.&vt.(使)疲劳(劳累) (高中英语单词)
• studied [´stʌdid] a.故意的；有计划的 (高中英语单词)
• mattress [´mætris] n.床垫 (高中英语单词)
• reproduction [,ri:prə´dʌkʃən] n.繁殖；翻版；再现 (英语四级单词)
• manual [´mænjuəl] a.用手(操作)的 n.手册 (英语四级单词)
• chicago [ʃi´kɑ:gəu] n.芝加哥 (英语四级单词)
• intercourse [´intəkɔ:s] n.交际；往来；交流 (英语四级单词)
• abstract [´æbstrækt] a.抽象的 n.提要 (英语四级单词)
• uneven [ʌn´i:vən] a.崎岖的；不匀的 (英语四级单词)
• erection [i´rekʃən] n.直立，建立；建筑物 (英语六级单词)
• sexual [´sekʃuəl] a.性(欲)的 (英语六级单词)
• frequency [´fri:kwənsi] n.频繁；周率 (英语六级单词)
• taking [´teikiŋ] a.迷人的 n.捕获物 (英语六级单词)