Sexual dysfunction

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Sexual dysfunction
Classification and external resources
ICD-10 F52
ICD-9 302.7
MeSH D020018

Sexual dysfunction or sexual malfunction is difficulty experienced by an individual or a couple during any stage of a normal sexual activity, including physical pleasure, desire, preference, arousal or orgasm. According to the DSM-5, sexual dysfunction requires a person to feel extreme distress and interpersonal strain for a minimum of 6 months (excluding substance or medication-induced sexual dysfunction).[1] Sexual dysfunctions can have a profound impact on an individual's perceived quality of sexual life.[2]

A thorough sexual history and assessment of general health and other sexual problems (if any) are very important. Assessing (performance) anxiety, guilt, stress and worry are integral to the optimal management of sexual dysfunction. Many of the sexual dysfunctions that are defined are based on the human sexual response cycle, proposed by William H. Masters and Virginia E. Johnson, and then modified by Helen Singer Kaplan.[3][4]

Categories[edit]

Sexual dysfunction disorders may be classified into four categories: sexual desire disorders, arousal disorders, orgasm disorders and pain disorders.

Sexual desire disorders[edit]

Sexual desire disorders or decreased libido are characterised by a lack or absence for some period of time of sexual desire or libido for sexual activity or of sexual fantasies. The condition ranges from a general lack of sexual desire to a lack of sexual desire for the current partner. The condition may have started after a period of normal sexual functioning or the person may always have had no/low sexual desire.

The causes vary considerably, but include a possible decrease in the production of normal estrogen in women or testosterone in both men and women. Other causes may be aging, fatigue, pregnancy, medications (such as the SSRIs) or psychiatric conditions, such as depression and anxiety.[5] Loss of libido from SSRIs usually reverses after SSRIs are discontinued, but in some cases it does not. This has been called PSSD; however, this is not a classification that would be found in any current medical text. While a number of causes for low sexual desire are often cited, only some of these have ever been the object of empirical research. Many rely entirely on the impressions of therapists.[6]

Sexual arousal disorders[edit]

Sexual arousal disorders were previously known as frigidity in women and impotence in men, though these have now been replaced with less judgmental terms. Impotence is now known as erectile dysfunction, and frigidity has been replaced with a number of terms describing specific problems with, for example, desire or arousal.

For both men and women, these conditions can manifest themselves as an aversion to, and avoidance of, sexual contact with a partner. In men, there may be partial or complete failure to attain or maintain an erection, or a lack of sexual excitement and pleasure in sexual activity.

There may be medical causes to these disorders, such as decreased blood flow or lack of vaginal lubrication. Chronic disease can also contribute, as well as the nature of the relationship between the partners.

Erectile dysfunction[edit]

Main article: Erectile dysfunction

Erectile dysfunction or impotence is a sexual dysfunction characterized by the inability to develop or maintain an erection of the penis. There are various underlying causes, such as damage to the nervi erigentes which prevents or delays erection, or diabetes as well as cardiovascular disease, which simply decreases blood flow to the tissue in the penis, many of which are medically reversible.

The causes of erectile dysfunction may be psychological or physical. Psychological erectile dysfunction can often be helped by almost anything that the patient believes in; there is a very strong placebo effect. Physical damage is much more severe. One leading physical cause of ED is continual or severe damage taken to the nervi erigentes. These nerves course beside the prostate arising from the sacral plexus and can be damaged in prostatic and colorectal surgeries.

Diseases are also common causes of erectile dysfunctional; especially in men. Diseases such as cardiovascular disease, multiple sclerosis, kidney failure, vascular disease and spinal cord injury are the source of erectile dysfunction.[7]

Due to its embarrassing nature and the shame felt by sufferers, the subject was taboo for a long time, and is the subject of many urban legends. Folk remedies have long been advocated, with some being advertised widely since the 1930s. The introduction of perhaps the first pharmacologically effective remedy for impotence, sildenafil (trade name Viagra), in the 1990s caused a wave of public attention, propelled in part by the news-worthiness of stories about it and heavy advertising.

It is estimated that around 30 million men in the United States and 152 million men worldwide suffer from Erectile Dysfunction.[8][9] However, social stigma, low health literacy and social taboos lead to under reporting which makes an accurate prevalence rate hard to determine.

The Latin term impotentia coeundi describes simple inability to insert the penis into the vagina. It is now mostly replaced by more precise terms.

Premature ejaculation[edit]

Main article: Premature ejaculation

Premature ejaculation is when ejaculation occurs before the partner achieves orgasm, or a mutually satisfactory length of time has passed during intercourse. There is no correct length of time for intercourse to last, but generally, premature ejaculation is thought to occur when ejaculation occurs in under 2 minutes from the time of the insertion of the penis.[10] For a diagnosis, the patient must have a chronic history of premature ejaculation, poor ejaculatory control, and the problem must cause feelings of dissatisfaction as well as distress the patient, the partner or both.[11]

Historically attributed to psychological causes, new theories suggest that premature ejaculation may have an underlying neurobiological cause which may lead to rapid ejaculation.[12]

Orgasm disorders[edit]

Main article: Anorgasmia

Orgasm disorders are persistent delays or absence of orgasm following a normal sexual excitement phase. The disorder can have physical, psychological, or pharmacological origins. SSRI antidepressants are a common pharmaceutical culprit, as they can delay orgasm or eliminate it entirely. A common physiological culprit of anorgasmia is menopause, where one in three women report problems obtaining an orgasm during sexual stimulation following menopause.[13]

Sexual pain disorders[edit]

Sexual pain disorders affect women almost exclusively and are also known as dyspareunia (painful intercourse) or vaginismus (an involuntary spasm of the muscles of the vaginal wall that interferes with intercourse).

Dyspareunia may be caused by insufficient lubrication (vaginal dryness) in women. Poor lubrication may result from insufficient excitement and stimulation, or from hormonal changes caused by menopause, pregnancy, or breast-feeding. Irritation from contraceptive creams and foams can also cause dryness, as can fear and anxiety about sex.

It is unclear exactly what causes vaginismus, but it is thought that past sexual trauma (such as rape or abuse) may play a role. Another female sexual pain disorder is called vulvodynia or vulvar vestibulitis. In this condition, women experience burning pain during sex which seems to be related to problems with the skin in the vulvar and vaginal areas. The cause is unknown.

Uncommon sexual disorders in men[edit]

Erectile dysfunction from vascular disease is usually seen only amongst elderly individuals who have atherosclerosis. Vascular disease is common in individuals who have diabetes, peripheral vascular disease, hypertension and those who smoke. Any time blood flow to the penis is impaired, erectile dysfunction is the end result.

Hormone deficiency is a relatively rare cause of erectile dysfunction. In individuals with testicular failure like in Klinefelter syndrome, or those who have had radiation therapy, chemotherapy or childhood exposure to mumps virus, the testes may fail and not produce testosterone. Other hormonal causes of erectile failure include brain tumors, hyperthyroidism, hypothyroidism or disorders of the adrenal gland.[14]

Structural abnormalities of the penis like Peyronie's disease can make sexual intercourse difficult. The disease is characterized by thick fibrous bands in the penis which leads to a deformed-looking penis.[15]

Drugs are also a cause of erectile dysfunction. Individuals who take drugs to lower blood pressure, uses antipsychotics, antidepressants, sedatives, narcotics, antacids or alcohol can have problems with sexual function and loss of libido.[16]

Priapism is a painful erection that occurs for several hours and occurs in the absence of sexual stimulation. This condition develops when blood gets trapped in the penis and is unable to drain out. If the condition is not promptly treated, it can lead to severe scarring and permanent loss of erectile function. The disorder occurs in young men and children. Individuals with sickle-cell disease and those who abuse certain medications can often develop this disorder.[17]

Causes[edit]

General[edit]

There are many factors which may result in a person experiencing a sexual dysfunction. These may result from emotional or physical causes. Emotional factors include interpersonal or psychological problems, which can be the result of depression, sexual fears or guilt, past sexual trauma, and sexual disorders,[18] among others.

Sexual dysfunction is especially common among people who have anxiety disorders. Ordinary anxiousness can obviously cause erectile dysfunction in men without psychiatric problems, but clinically diagnosable disorders such as panic disorder commonly cause avoidance of intercourse and premature ejaculation.[citation needed] Pain during intercourse is often a comorbidity of anxiety disorders among women.[5]

Physical factors that can lead to sexual dysfunctions include the use of drugs, such as alcohol, nicotine, narcotics, stimulants, antihypertensives, antihistamines, and some psychotherapeutic drugs.[19] For women, almost any physiological change that affects the reproductive system—premenstrual syndrome, pregnancy and the postpartum period, menopause—can have an adverse effect on libido.[19] Injuries to the back may also impact sexual activity, as can problems with an enlarged prostate gland, problems with blood supply, or nerve damage (as in spinal cord injuries). Diseases such as diabetic neuropathy, multiple sclerosis, tumors, and, rarely, tertiary syphilis may also impact the activity, as could the failure of various organ systems (such as the heart and lungs), endocrine disorders (thyroid, pituitary, or adrenal gland problems), hormonal deficiencies (low testosterone, other androgens, or estrogen) and some birth defects.

In the context of heterosexual relationships, one of the main reasons for the decline in sexual activity among these couples is the male partner experiencing erectile dysfunction. This can be very distressing for the male partner, causing poor body image, and it can also be a major source of low desire for these men.[20] In aging women, it is natural for the vagina to narrow and become atrophied. If a woman has not been participating in sexual activity regularly (in particular, activities involving vaginal penetration) with her partner, if she does decide to engage in penetrative intercourse, she will not be able to immediately accommodate a penis without risking pain or injury.[20] This can turn into a vicious cycle, often leading to female sexual dysfunction.[20]

Female sexual dysfunction[edit]

Several theories have looked at female sexual dysfunction, from medical to psychological perspectives. Three social psychological theories include: the self-perception theory, the overjustification hypothesis, and the insufficient justification hypothesis:

  • Self-perception theory: people make attributions about their own attitudes, feelings, and behaviours by relying on their observations of external behaviours and the circumstances in which those behaviours occur
  • Overjustification hypothesis: when an external reward is given to a person for performing an intrinsically rewarding activity, the person’s intrinsic interest will decrease
  • Insufficient justification: based on the classic cognitive dissonance theory (inconsistency between two cognitions or between a cognition and a behavior will create discomfort), this theory states that people will alter one of the cognitions or behaviours to restore consistency and reduce distress

The importance of how a woman perceives her behavior should not be underestimated. Many women perceived sex as a chore as opposed to a pleasurable experience, and they tend to consider themselves sexually inadequate, which in turn does not motivate them to engage in sexual activity.[20] Several factors influence a women’s perception of her sexual life. These can include: race, her gender, ethnicity, educational background, socioeconomic status, sexual orientation, financial resources, culture, and religion.[20] Cultural differences are also present in how women view menopause and its impact on health, self-image, and sexuality. A study has found that African American women are the most optimistic about menopausal life; Caucasian women are the most anxious, Asian women are the most inhibited about their symptoms, and Hispanic women are the most stoic.[20]

Menopause[edit]

Research on sexual dysfunction is more difficult in menopausal women because of the changes that are taking place during their specific physiological state.[21] The female sexual response system is complex and even today, not fully understood. The most prevalent of female sexual dysfunctions that have been linked to menopause include lack of desire and libido; these are predominantly associated with hormonal physiology.[2] Specifically, it is the decline in serum estrogens that causes these changes in sexual functioning. Androgen depletion may also play a role, but currently this is less clear. The hormonal changes that take place during the menopausal transition have been suggested to affect women’s sexual response through several mechanisms, some more conclusive than others.[2]

Many studies have demonstrated the dramatic changes in sexual functioning that can take place during this transition phase. Studies have found that as many as 25% of menopausal women are unable to experience orgasm, 20% reported no pleasure with sex, and another 20% had lubrication difficulties.[21] While there has been controversy over whether these are due to the natural causes of aging or whether they’re specific to the menopause transition, it seems like most studies have come to the conclusion that decreases in sexual interest and sexual satisfaction are due to menopause.[21] Furthermore, one study found that all aspects of sexual life were significantly compromised in postmenopausal women without hormone replacement therapy (HRT) compared to both menstruating women and postmenopausal women with HRT.[21]

Aging in women[edit]

Whether or not aging directly affects women’s sexual functioning during menopause is another area of controversy. However, many studies, including Hayes and Dennerstein’s critical review, have demonstrated that aging has a powerful impact on sexual function and dysfunction in women, specifically in the areas of desire, sexual interest, and frequency of orgasm.[2][20][22] In addition, Dennerstien and colleagues found that the primary predictor of sexual response throughout menopause is prior sexual functioning.[2] This means that it is important to understand how the physiological changes in men and women can affect their sexual desire.[20] Despite the seemingly negative impact that menopause can have on sexuality and sexual functioning, sexual confidence and well-being can improve with age and menopausal status.[2] Furthermore, the impact that a relationship status can have on quality of life is often underestimated.

Testosterone, along with its metabolite dihydrotestosterone, is extremely important to normal sexual functioning in men and women. Dihydrotestosterone is the most prevalent androgen in both men and women.[20] Testosterone levels in women at age 60 are, on average, about half of what they were before the women were 40. Although this decline is gradual for most women, those who’ve undergone bilateral oophorectomy experience a sudden drop in testosterone levels; this is because the ovaries produce 40% of the body’s circulating testosterone.[20]

Sexual desire has been related to three separate components: drive, beliefs and values, and motivation.[20] Particularly in postmenopausal women, drive fades and is no longer the initial step in a woman's sexual response (if it ever was).[20]

List of disorders[edit]

Physical or psychological sexual disorders under the DSM[edit]

The fourth edition of the Diagnostic and Statistical Manual of Mental Disorders lists the following sexual dysfunctions:

Additional DSM sexual disorders that are not sexual dysfunctions include:

Other sexual problems[edit]

Treatment for males[edit]

Several decades ago the medical community believed the majority of sexual dysfunction cases were related to psychological issues. Although this may be true for a portion of men, the vast majority of cases have now been identified as having a physical cause or correlation.[23] If the sexual dysfunction is deemed to have a psychological component or cause, psychotherapy can help. Situational anxiety arises from an earlier bad incident or lack of experience. This anxiety often leads to development of fear towards sexual activity and avoidance. In return evading leads to a cycle of increased anxiety and desensitization of the penis.[24] In some cases, erectile dysfunction may be due to marital disharmony. Marriage counseling sessions are recommended in this situation.

Lifestyle changes such as discontinuing smoking, drug or alcohol abuse can also help in some types of erectile dysfunction.[25] Several oral medications like Viagra, Cialis and Levitra have become available to help people with erectile dysfunction and have become first line therapy. These medications provide an easy, safe, and effective treatment solution for approximately 60% of men. In the rest, the medications may not work because of wrong diagnosis or chronic history.

Another type of medication that is effective in roughly 85% of men is called intracavernous pharmacotherapy and involves injecting a vasodilator drug directly into the penis in order to stimulate an erection.[26] This method has an increased risk of priapism if used in conjunction with other treatments, and localized pain.[11]

When conservative therapies fail, are an unsatisfactory treatment option, or are contraindicated for use, the insertion of a penile prosthesis, or penile implant, may be selected by the patient. Technological advances have made the insertion of a penile prosthesis a safe option for the treatment of erectile dysfunction which provides the highest patient and partner satisfaction rates of all available ED treatment options.[27]

Treatment for females[edit]

Although there are no approved pharmaceuticals for addressing female sexual disorders, several are under investigation for their effectiveness.[28] A vacuum device is the only approved medical device for arousal and orgasm disorders. It is designed to increase blood flow to the clitoris and external genitalia.[28] Women experiencing pain with intercourse are often prescribed pain relievers or desensitizing agents. Others are prescribed lubricants and/or hormone therapy.[28] Many patients with female sexual dysfunction are often also referred to a counselor or therapist for psychosocial counseling.[28]

Hormone replacement therapy[edit]

Hormone replacement therapy (HRT) has the ability to improve a woman's sexual satisfaction.[21] Estrogens are responsible for the maintenance of collagen, elastic fibers, and vasoculature of the urogenital tract, all of which are important in maintaining vaginal structure and functional integrity; they are also important for maintaining vaginal pH and moisture levels, both of which aid in keeping the tissues lubricated and protected.[2] Prolonged estrogen deficiency leads to atrophy, fibrosis, and reduced blood flow to the urogenital tract, which is what causes menopausal symptoms such as vaginal dryness and pain related to sexual activity and/or intercourse.[2] It has been consistently demonstrated that women with lower sexual functioning have lower estradiol levels.[2]

Even though estrogen replacement therapies (ERT) and HRTs have been shown to be effective for the treatment of vaginal atrophy, there has not been consistent evidence to suggest that these therapies increase sexual desire or sexual activity; therefore, many women with sexual dysfunctions remain unresponsive.[29] There are two broad categories that address the management of sexual well being during menopause: pharmacological treatments that focus on correcting these difficulties, and psychological interventions. Because of the complexity of the female reproductive system, which includes a psychological aspect, it is not surprising that a female Viagra has not been found to work in women. Both the treatment and management of sexual functioning during the menopausal period should be unique to the individual based on her health history and her current needs.[29]

Androgen therapy is one method of pharmacological treatments that has been used for hypoactive sexual desire disorder (HSDD). This is generally more commonly used among women who have had an oophorectomy or who are in a postmenopausal state. However, like most treatments, this is also controversial. One study found that after a 24-week trial, those women taking androgens had significantly higher scores of sexual desire compared to a placebo group.[2] As with all pharmacological drugs, there are side effects in using androgens, which include hirutism, acne, ploycythaemia, increased high-density lipoproteins, cardiovascular risks, and endometrial hyperplasia is a possibility in women without hysterectomy.[2] This is another area in which long-term use has not been demonstrated. Alternative treatments include topical estrogen creams and gels can be applied to the vulva or vagina area to treat vaginal dryness and atrophy.[2]

Clinical studies[edit]

In modern times, the genuine clinical study of sexual problems is usually dated back no further than 1970 when Masters and Johnson's Human Sexual Inadequacy was published. It was the result of over a decade of work at the Reproductive Biology Research Foundation in St. Louis, involving 790 cases. The work grew from Masters and Johnson's earlier Human Sexual Response (1966).

Prior to Masters and Johnson the clinical approach to sexual problems was largely derived from the thinking of Freud. It was held with psychopathology and approached with a certain pessimism regarding the chance of help or improvement. Sexual problems were merely symptoms of a deeper malaise and the diagnostic approach was from the psychopathological. There was little distinction between difficulties in function and variations nor between perversion and problems. Despite work by psychotherapists such as Balint sexual difficulties were crudely split into frigidity or impotence, terms which too soon acquired negative connotations in popular culture.

The achievement of Human Sexual Inadequacy was to move thinking from psychopathology to learning, only if a problem did not respond to educative treatment would psychopathological problems be considered. Also treatment was directed at couples, whereas before partners would be seen individually. Masters and Johnson saw that sex was a joint act. They believed that sexual communication was the key issue to sexual problems not the specifics of an individual problem. They also proposed co-therapy, a matching pair of therapists to the clients, arguing that a lone male therapist could not fully comprehend female difficulties.

The basic Masters and Johnson treatment program was an intensive two-week program to develop efficient sexual communication. Couple-based and therapist led the program began with discussion and then sensate focus between the couple to develop shared experiences. From the experiences specific difficulties could be determined and approached with a specific therapy. In a limited number of male only cases (41) Masters and Johnson had developed the use of a female surrogate, an approach they soon abandoned over the ethical, legal and other problems it raised.

In defining the range of sexual problems Masters and Johnson defined a boundary between dysfunction and deviations. Dysfunctions were transitory and experienced by the majority of people, dysfunctions bounded male primary or secondary impotence, premature ejaculation, ejaculatory incompetence; female primary orgasmic dysfunction and situational orgasmic dysfunction; pain during intercourse (dyspareunia) and vaginismus. According to Masters and Johnson sexual arousal and climax are a normal physiological process of every functionally intact adult, but despite being autonomic it can be inhibited. Masters and Johnson treatment program for dysfunction was 81.1% successful.

Despite the work of Masters and Johnson the field in the US was quickly overrun by enthusiastic rather than systematic approaches, blurring the space between 'enrichment' and therapy. Although it has been argued that the impact of the work was such that it would be impossible to repeat such a clean experiment.

See also[edit]

References[edit]

  1. ^ Nolen-Hoeksema, Susan (2014). Abnormal Psychology. 2 Penn Plaza, New York, NY 10121: McGraw-Hill. pp. 366–367. ISBN 978-1-259-06072-4. 
  2. ^ a b c d e f g h i j k l Eden, K.J., & Wylie, K.R. (2009). Quality of sexual life and menopause. Women’s Health, 5 (4), 385-396. doi:10.2217/whe.09.24
  3. ^ Masters, W. H. & Johnson, V. E. (1970). Human Sexual Inadequacy. Boston: Little, Brown, & Co.
  4. ^ Kaplan, H. S. (1974). The New Sex Therapy: Active Treatment of Sexual Dysfunctions. New York: Brunner/Mazel, Inc.
  5. ^ a b Coretti G and Baldi I (August 1, 2007). "The Relationship Between Anxiety Disorders and Sexual Dysfunction". Psychiatric Times 24 (9). 
  6. ^ Maurice, William (2007): “Sexual Desire Disorders in Men.” in ed. Leiblum, Sandra: Principles and Practice of Sex Therapy (4th ed.) The Guilford Press. New York
  7. ^ Nolen-Hoeksema, S. (2013). Sexual Dysfnctions. In Abnormal Psychology. McGraw Hill Education.
  8. ^ NIH. Consensus Development Panel on Impotence. Impotence. Journal of the American Medical Association. 1993;270: 83 - 90
  9. ^ Ayta I, Mckinlay J, Krane R. The likely worldwide increase in erectile dysfunction between 1995 and 2025. BJU Int 1999; 84(1): 50-56.
  10. ^ Waldinger M.D.,Berenden H.H., Blok B.F., et al. Premature Ejaculation and Serotengeric Anti-depressants - Induced Delayed Ejaculation: The Involvement of the Serotonergic System. Behavioural Brain Res. 1998;92(2): 111-118
  11. ^ a b Diaz V.A. & Close J.D. Male Sexual Dysfunction Primary Care 2010;37(3): 473 - 489.'
  12. ^ Lauman E.O., Nicolosi, A., Glasser D.B., et al. Sexual Problems among women and men aged 40 to 80 years: Prevalence and Correlates Identified in a GLobal Study of Sexual Attitudes and Behaviours. International Journal of Impotence Research. 2005;7(1): 39 - 57.
  13. ^ Nolen-Hoeksema, Susan. "Abnormal Psychology". McGraw-Hill Humanities/Social Sciences/Languages; 6 Edition, 2013. p.368.
  14. ^ Strange sexual disorders Ask Men. Retrieved on February 18, 2010
  15. ^ Analysis of abnormal sexual disturbances 2010-02-18[unreliable medical source?]
  16. ^ Gupta, A; Chaudhry, M; Elewski, B (2003). "Tinea corporis, tinea cruris, tinea nigra, and piedra". Dermatologic Clinics 21 (3): 395–400, v. doi:10.1016/S0733-8635(03)00031-7. PMID 12956194. 
  17. ^ Priapism in Emergency Medicine, eMedicine. Retrieved on 2010-02-18
  18. ^ Michetti, P M; Rossi, R; Bonanno, D; Tiesi, A; Simonelli, C (2005). "Male sexuality and regulation of emotions: a study on the association between alexithymia and erectile dysfunction (ED)". International Journal of Impotence Research 18 (2): 170–4. doi:10.1038/sj.ijir.3901386. PMID 16151475. 
  19. ^ a b Saks BR (April 15, 2008). "Common issues in female sexual dysfunction". Psychiatric Times 25 (5). 
  20. ^ a b c d e f g h i j k l Kingsberg, S.A. (2002). The impact of aging on sexual function in women and their partners. Archives of Sexual Behaviour, 31(5), 431-437. Retrieved from: http://link.springer.com/article/10.1023/A:1019844209233
  21. ^ a b c d e Gonzalez, Maria (May 24, 2004). "Autistic teen's film wins recognition". Ventura County Star. p. 1. 
  22. ^ Edward O. Laumann, Anthony Paik, and Raymond C. Rosen. (1999). "Sexual Dysfunction in the United States: Prevalence and Predictors." JAMA: The Journal of the American Medical Association 281(6):537-44.
  23. ^ Jarow J, Nana-Sinkam P, Sabbagh M. Outcome analysis of goal directed therapy for impotence. J Urol 1996; 155: 1609-1612
  24. ^ How to Get Rid of Sexual Disorders and Dysfunction Online guide against depression. Retrieved on 2010-02-18
  25. ^ Merck Sharpe & Dohme. "Male genital and sexual disorders" 2010-02-18.
  26. ^ Rodríguez Vela, L; Moncada Iribarren, I; Gonzalvo Ibarra, A; Sáenz de Tejada y Gorman I (1998). "Treatment of erectile dysfunction using intracavernous pharmacotherapy". Actas urologicas espanolas 22 (4): 291–319. PMID 9658642. 
  27. ^ Rajpurkar A, Dhabuwala C. Comparison of satisfaction rates and erectile function in patients treated with sildenafil, intracavernous prostaglandin E1 and penile implant surgery for erectile dysfunction in urology practice. J Urol 2003; 170: 159-163
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  29. ^ a b Nappi, R.E. et al., (2006). Clitoral stimulation in postmenopausal women with sexual dysfunction: A pilot randomized study with hormone therapy. European Menopause Journal, 55, 288-295

Further reading[edit]

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