An effect on the subjective sexual response in premenopausal women with sexual arousal disorder by bremelanotide (PT-141), a melanocortin receptor agonist

Melanocortin 4 receptor signaling in Sim1 neurons permits sexual receptivity in female mice

Introduction

Female sexual dysfunction affects approximately 40% of women in the United States, yet few therapeutic options exist for these patients. The melanocortin system is a new treatment target for hypoactive sexual desire disorder (HSDD), but the neuronal pathways involved are unclear.

Methods

In this study, the sexual behavior of female MC4R knockout mice lacking melanocortin 4 receptors (MC4Rs) was examined. The mice were then bred to express MC4Rs exclusively on Sim1 neurons (tbMC4RSim1 mice) or on oxytocin neurons (tbMC4ROxt mice) to examine the effect on sexual responsiveness.

Results

MC4R knockout mice were found to approach males less and have reduced receptivity to copulation, as indicated by a low lordosis quotient. These changes were independent of body weight. Lordosis behavior was normalized in tbMC4RSim1 mice and improved in tbMC4ROxt mice. In contrast, approach behavior was unchanged in tbMC4RSim1 mice but greatly increased in tbMC4ROxt animals. The changes were independent of melanocortin-driven metabolic effects.

Discussion

These results implicate MC4R signaling in Oxt neurons in appetitive behaviors and MC4R signaling in Sim1 neurons in female sexual receptivity, while suggesting melanocortin-driven sexual function does not rely on metabolic neural circuits.

An evaluation of bremelanotide injection for the treatment of hypoactive sexual desire disorder

INTRODUCTION

Female sexual response implies a deep intertwining between psychosocial and neurobiological mediators. Regulation of central melanocortin signaling may enhance sexual desire. In premenopausal women with hypoactive sexual desire disorder (HSDD), melanocortin receptor agonist bremelanotide (Vyleesi) has been hypothesized to trigger excitatory brain pathways.

AREAS COVERED

Hereby we summarize bremelanotide's proposed mechanism of action, pharmacokinetics, efficacy and safety data derived from clinical trials. A literature search of peer-reviewed publications on the current evidence on the pharmacotherapy with bremelanotide was performed using the PubMed database.

EXPERT OPINION

Bremelanotide appears to be moderately safe and well-tolerated; the most common adverse reaction is nausea (40%). Although data from clinical trials demonstrated a significant change in validated questionnaires, the overall clinical benefit appears to be modest. However, these results should be interpreted in the light of the dramatic challenges in conducting well-designed clinical trials for female sexual dysfunction, due to the significant placebo effect of pharmacotherapy, and the frequent use of outcome measures that are likely to be highly susceptible to expectation biases, such as long periods of recall of sexual and emotional response.

The neurobiology of bremelanotide for the treatment of hypoactive sexual desire disorder in premenopausal women

Hypoactive sexual desire disorder (HSDD) is a common female sexual dysfunction and is estimated to affect approximately 10% of women in the United States. It has been suggested that HSDD is associated with an imbalance of hormone and neurotransmitter levels in the brain, resulting in decreased excitation, increased inhibition, or a combination of both. Evidence suggests neurotransmitters, including dopamine (DA), norepinephrine, and serotonin, as well as hormones such as estradiol and testosterone, contribute to female sexual desire and response. Current treatments for HSDD include psychotherapy, and two US Food and Drug Administration-approved medications for premenopausal women: flibanserin, a serotonin mixed agonist and antagonist, and bremelanotide, a melanocortin receptor (MCR) agonist. Melanocortins are endogenous neuropeptides associated with the excitatory pathway of the female sexual response system. MCRs are found throughout the body, including the brain. Bremelanotide is an MCR agonist that nonselectively activates several of the receptor subtypes, of which subtype 4 (MC4R) is the most relevant at therapeutic doses. MC4R is predominantly expressed in the medial preoptic area (mPOA) of the hypothalamus in the brain, and is important for female sexual function. Animal studies suggest that bremelanotide may affect female sexual desire by activating presynaptic MC4Rs on neurons in the mPOA of the hypothalamus, leading to increased release of DA, an excitatory neurotransmitter that increases sexual desire. This review presents what is known about the mechanism of action of bremelanotide in the context of treating HSDD.

Sacubitril/Valsartan Improves Sexual Function and Fibrosis of the Clitoral and Vaginal Tissues in Female Spontaneously Hypertensive Rats

ABSTRACT

Female sexual dysfunction is common in hypertension. The effects of sacubitril/valsartan (SAC/VAL) as a potential therapy for hypertension and heart failure have not been studied in relation to sexual function and genital fibrosis in female spontaneously hypertensive rats (SHRs). Thirty female SHRs were administered VAL, SAC/VAL, or saline. Ten normotensive female Wistar-Kyoto (WKY) rats were included in the control group. We assessed estrous cyclicity and sexual behavior in the female rats. In addition, the morphology of clitoral and vaginal tissues was evaluated by histological analyses. Western blotting and enzyme-linked immunosorbent assays were used to assess the levels of fibrotic markers in vaginal and clitoral tissues. Furthermore, the protein levels of phosphatase and tensin homolog deleted from chromosome 10 (PTEN), phosphoinositide-3-kinase (PI3K), and AKT expression were measured by Western blotting. SAC/VAL treatment improved hypertension-induced sexual dysfunction, exhibited as a prolonged estrus phase, increased receptivity and proceptive events, and decreased aggressive events, compared with those of VAL treatment and control SHRs without treatments. In addition, SAC/VAL-treated SHRs had lower levels of fibrotic markers, estradiol, and estrogen receptor α/β than the levels of VAL-treated SHRs or SHRs without treatment. Moreover, SAC/VAL decreased p-PTEN expression and increased p-PI3K and p-AKT expression at the protein level compared with those in VAL treatment alone. VAL and SAC/VAL treatments have significantly increased sexual receptivity and proceptivity, decreased aggressiveness, and improved the fibrosis of vaginal and clitoral tissues in female SHRs. However, SAC/VAL treatment shows more effective results compared with VAL treatment, which may be related to the PTEN/PI3K/AKT pathway.

Bremelanotide for Treatment of Female Hypoactive Sexual Desire

Hypoactive sexual desire disorder (HSDD) is a persistent deficiency or absence of sexual fantasies and desire resulting in significant distress or interpersonal difficulty. Women with this disorder may display a lack of motivation for sexual activity, reduced responsiveness to erotic cues, a loss of interest during sexual activity, and avoidance of situations that could lead to sexual activity. The pathophysiology of HSDD is thought to be centered around inhibitory and excitatory hormones, neurotransmitters, and specific brain anatomy. Due to the multifactorial nature of HSDD, treatment can be complex and must attempt to target the biological and psychosocial aspects of the disorder. Bremelanotide is a melanocortin receptor agonist and has been recently approved by the FDA to treat HSDD. Bremelanotide is administered intranasally or as a subcutaneous injection. The recommended dosage of bremelanotide is 1.75 mg injected subcutaneously in the abdomen or thigh at least 45 min before sexual activity. Studies showed improvements in desire, arousal, and orgasm scores when 1.75 mg of bremelanotide was administered before sexual activity compared to a placebo. Bremelanotide is a promising way to treat HSDD.

Bremelanotide: First Approval

Bremelanotide (Vyleesi™) is a melanocortin receptor agonist recently approved in the USA for the treatment of premenopausal women with acquired, generalized hypoactive sexual desire disorder (HSDD), as characterized by low sexual desire that causes marked distress or interpersonal difficulty. It is a self-administered, on-demand subcutaneous therapy. Initially developed by Palatin Technologies who sponsored the Phase 3 clinical trials, bremelanotide was subsequently out-licensed to AMAG Pharmaceuticals Inc. for exclusive North American rights to develop and commercialize the drug, including submitting the New Drug Application to the US FDA. Bremelanotide is a synthetic peptide analogue of the neuropeptide hormone alpha melanocyte-stimulating hormone (α-MSH) with high affinity for the melanocortin type 4 receptor (thought to be important for sexual function), giving it the potential to modulate brain pathways involved in sexual response. This article summarizes the milestones in the development of bremelanotide leading to this first regulatory approval.

Bremelanotide: New Drug Approved for Treating Hypoactive Sexual Desire Disorder

Objective: To review data regarding bremelanotide, a recently approved therapy for hypoactive sexual desire disorder (HSDD). Data Sources: Literature search of Medline, SCOPUS, and EMBASE was performed using the search terms bremelanotide, bremelanotide injection, Vyleesi, and melanocortin 4 receptor agonist between January 1, 1996, and December 15, 2019. Reference lists from included articles were also reviewed for pertinent citations. Study Selection/Data Extraction: We included phase 2 and 3 trials of bremelanotide. There were 2 reports of phase 3 trials and 2 reports of phase 2 trials. Additional information from supplementary analyses was also referenced. Data Synthesis: Bremelanotide demonstrates significant improvement in desire and a significant decrease in distress related to lack of desire. The most common adverse effects include nausea (39.9%), facial flushing (20.4%), and headache (11%). Relevance to Patient Care and Clinical Practice: Bremelanotide is the second Food and Drug Administration–approved medication for the treatment of HSDD. Bremelanotide’s place in therapy is unknown, as the HSDD guidelines were last updated in 2017. Although the trials met statistical significance for change in sexual desire elements and distress related to sexual desire, the clinical benefit may only be modest. Conclusion: Bremelanotide is a subcutaneous injection that can be administered as needed approximately 45 minutes prior to sexual activity. Bremelanotide is safe and has limited drug-drug interactions, including no clinically significant interactions with ethanol. Prescribing guidelines recommend no more than 1 dose in 24 hours and no more than 8 doses per month. Individuals should discontinue use after 8 weeks without benefit.

Sexual Function Post-Breast Cancer

The consequences of estrogen deprivation and therapeutic interventions such as radiation, chemotherapy and surgery have a significant negative impact on libido, sexual arousal, orgasmic function and the ability to have pleasurable intercourse. Evaluation and treatment of female sexual dysfunction is a significant unmet need in the breast cancer survivor in spite of the availability of safe and effective treatments.

Phase I Randomized Placebo-controlled, Double-blind Study of the Safety and Tolerability of Bremelanotide Coadministered With Ethanol in Healthy Male and Female Participants

PURPOSE

This was a Phase I study to evaluate the safety, tolerability, and hemodynamic and pharmacokinetic effects of bremelanotide (BMT) coadministered with ethanol to healthy male and female participants.

METHODS

This was a randomized, placebo-controlled, double-blind, 3-period, 3-way crossover study. Individuals meeting the inclusion/exclusion criteria received BMT or placebo with or without ethanol at the research facility for 7 consecutive days. Participants were randomized to receive 1 of 6 treatment paths; each participant received single intranasal doses of BMT (20 mg) or placebo on days 1, 4, and 7, with or without oral ethanol (0.6 g/kg) while in a fasted state. The intranasal 20-mg dose of BMT has an exposure equivalent to ~1 to 2 times the subcutaneous dose currently being evaluated in Phase III studies. Vital signs, self-rated sedation scores, nursing and medical observations, and spontaneous reporting by participants provided the basis for evaluation of adverse events. A physical examination and a resting 12-lead electrocardiogram were performed at baseline and on study day 7. Blood and urine samples were obtained for clinical safety profile laboratory tests.

FINDINGS

A total of 24 participants were enrolled (12 men; 12 women) and completed the study. Single doses of 20 mg intranasal BMT, administered with or without 0.6 g/kg ethanol, were found to be safe and generally well tolerated with mean maximum ethanol concentrations exceeding 80 mg/dL in women. No clinically significant pharmacokinetic interactions were found between ethanol and BMT either overall or by sex. No significant drug-related hypotensive or orthostatic hypotensive effects were noted. Treatment with BMT did not result in an increased frequency of treatment-emergent adverse events, and no participants discontinued the study because of adverse events. Physical examination, electrocardiography, and laboratory tests disclosed no clinically significant changes.

IMPLICATIONS

Female sexual dysfunction is a multifactorial condition with anatomic, physiologic, medical, psychological, and social components. BMT is a synthetic peptide analogue of the naturally occurring hormone α-melanocyte-stimulating hormone and a melanocortin receptor agonist that is being developed for the treatment of hypoactive sexual desire disorder. Its mechanism of action involves activation of endogenous melanocortin hormone pathways involved in the sexual desire and arousal response. The results of this Phase I study found that BMT and ethanol can be safely coadministered and are generally well tolerated with no reports of drug-related serious adverse events. Phase III trials of subcutaneous BMT for the treatment of hypoactive sexual desire disorder in premenopausal women are in progress. ClinicalTrials.gov identifiers NCT02338960 and NCT02333071.

Mindfulness-Based Sex Therapy Improves Genital-Subjective Arousal Concordance in Women With Sexual Desire/Arousal Difficulties

There is emerging evidence for the efficacy of mindfulness-based interventions for improving women's sexual functioning. To date, this literature has been limited to self-reports of sexual response and distress. Sexual arousal concordance-the degree of agreement between self-reported sexual arousal and psychophysiological sexual response-has been of interest due to the speculation that it may be a key component to healthy sexual functioning in women. We examined the effects of mindfulness-based sex therapy on sexual arousal concordance in a sample of women with sexual desire/arousal difficulties (n = 79, M age 40.8 years) who participated in an in-laboratory assessment of sexual arousal using a vaginal photoplethysmograph before and after four sessions of group mindfulness-based sex therapy. Genital-subjective sexual arousal concordance significantly increased from pre-treatment levels, with changes in subjective sexual arousal predicting contemporaneous genital sexual arousal (but not the reverse). These findings have implications for our understanding of the mechanisms by which mindfulness-based sex therapy improves sexual functioning in women, and suggest that such treatment may lead to an integration of physical and subjective arousal processes. Moreover, our findings suggest that future research might consider the adoption of sexual arousal concordance as a relevant endpoint in treatment outcome research of women with sexual desire/arousal concerns.

Bremelanotide for female sexual dysfunctions in premenopausal women: a randomized, placebo-controlled dose-finding trial

Aim: Evaluate efficacy/safety of bremelanotide (BMT), a melanocortin-receptor-4 agonist, to treat female sexual dysfunctions in premenopausal women. Methods: Patients randomized to receive placebo or BMT 0.75, 1.25 or 1.75 mg self-administered subcutaneously, as desired, over 12 weeks. Primary end point was change in satisfying sexual events/month. Secondary end points included total score changes on female sexual function index and female sexual distress scale-desire/arousal/orgasm. Results: Efficacy data, n = 327. For 1.25/1.75-mg pooled versus placebo, mean changes from baseline to study end were +0.7 versus +0.2 satisfying sexual events/month (p = 0.0180), +3.6 versus +1.9 female sexual function index total score (p = 0.0017), −11.1 versus −6.8 female sexual distress scale-desire/arousal/orgasm total score (p = 0.0014). Adverse events: nausea, flushing, headache. Conclusion: In premenopausal women with female sexual dysfunctions, self-administered, as desired, subcutaneous BMT was safe, effective, and well tolerated (NCT01382719).

The Female Sexual Response: Current Models, Neurobiological Underpinnings and Agents Currently Approved or Under Investigation for the Treatment of Hypoactive Sexual Desire Disorder

How a woman responds to sexual cues is highly dependent on a number of distinct, yet related, factors. Researchers have attempted to explain the female sexual response for decades, but no single model reigns supreme. Proper female sexual function relies on the interplay of somatic, psychosocial and neurobiological factors; misregulation of any of these components could result in sexual dysfunction. The most common sexual dysfunction disorder is hypoactive sexual desire disorder (HSDD). HSDD is a disorder affecting women across the world; a recent in-person diagnostic interview study conducted in the USA found that an estimated 7.4% of US women suffer from HSDD. Despite the disorder's prevalence, it is often overlooked as a formal diagnosis. In a survey of primary care physicians and obstetrics/gynaecology specialists, the number one reason for not assigning an HSDD diagnosis was the lack of a safe and effective therapy approved by the US Food and Drug Administration (FDA). This changed with the recent FDA approval of flibanserin (Addyi™) for the treatment of premenopausal women with acquired, generalized HSDD; there are still, however, no treatments approved outside the USA. HSDD is characterized by a marked decrease in sexual desire, an absence of motivation (also known as avolition) to engage in sexual activity, and the condition's hallmark symptom, marked patient distress. Research suggests that HSDD may arise from an imbalance of the excitatory and inhibitory neurobiological pathways that regulate the mammalian sexual response; top-down inhibition from the prefrontal cortex may be hyperactive, and/or bottom-up excitation to the limbic system may be hypoactive. Key neuromodulators for the excitatory pathways include norepinephrine, oxytocin, dopamine and melanocortins. Serotonin, opioids and endocannabinoids serve as key neuromodulators for the inhibitory pathways. Evolving treatment strategies have relied heavily on these crucial research findings, as many of the agents currently being investigated as treatment options for HSDD target and influence key players within these excitatory and inhibitory pathways, including various hormone therapies and centrally acting drugs, such as buspirone, bupropion and bremelanotide.

Animal Models for the Study of Female Sexual Dysfunction

INTRODUCTION

Significant progress has been made in elucidating the physiological and pharmacological mechanisms of female sexual function through preclinical animal research. The continued development of animal models is vital for the understanding and treatment of the many diverse disorders that occur in women.

AIM

To provide an updated review of the experimental models evaluating female sexual function that may be useful for clinical translation.

METHODS

Review of English written, peer-reviewed literature, primarily from 2000 to 2012, that described studies on female sexual behavior related to motivation, arousal, physiological monitoring of genital function and urogenital pain.

MAIN OUTCOMES MEASURES

Analysis of supporting evidence for the suitability of the animal model to provide measurable indices related to desire, arousal, reward, orgasm, and pelvic pain.

RESULTS

The development of female animal models has provided important insights in the peripheral and central processes regulating sexual function. Behavioral models of sexual desire, motivation, and reward are well developed. Central arousal and orgasmic responses are less well understood, compared with the physiological changes associated with genital arousal. Models of nociception are useful for replicating symptoms and identifying the neurobiological pathways involved. While in some cases translation to women correlates with the findings in animals, the requirement of circulating hormones for sexual receptivity in rodents and the multifactorial nature of women's sexual function requires better designed studies and careful analysis. The current models have studied sexual dysfunction or pelvic pain in isolation; combining these aspects would help to elucidate interactions of the pathophysiology of pain and sexual dysfunction.

CONCLUSIONS

Basic research in animals has been vital for understanding the anatomy, neurobiology, and physiological mechanisms underlying sexual function and urogenital pain. These models are important for understanding the etiology of female sexual function and for future development of pharmacological treatments for sexual dysfunctions with or without pain. Marson L, Giamberardino MA, Costantini R, Czakanski P, and Wesselmann U. Animal models for the study of female sexual dysfunction. Sex Med Rev 2013;1:108-122.

Conditional expression of Pomc in the Lepr-positive subpopulation of POMC neurons is sufficient for normal energy homeostasis and metabolism

Peptides derived from the proopiomelanocortin (POMC) precursor are critical for the normal regulation of many physiological parameters, and POMC deficiency results in severe obesity and metabolic dysfunction. Conversely, augmentation of central nervous system melanocortin function is a promising therapeutic avenue for obesity and diabetes but is confounded by detrimental cardiovascular effects including hypertension. Because the hypothalamic population of POMC-expressing neurons is neurochemically and neuroanatomically heterogeneous, there is interest in the possible dissociation of functionally distinct POMC neuron subpopulations. We used a Cre recombinase-dependent and hypothalamus-specific reactivatable PomcNEO allele to restrict Pomc expression to hypothalamic neurons expressing leptin receptor (Lepr) in mice. In contrast to mice with total hypothalamic Pomc deficiency, which are severely obese, mice with Lepr-restricted Pomc expression displayed fully normal body weight, food consumption, glucose homeostasis, and locomotor activity. Thus, Lepr+ POMC neurons, which constitute approximately two-thirds of the total POMC neuron population, are sufficient for normal regulation of these parameters. This functional dissociation approach represents a promising avenue for isolating therapeutically relevant POMC neuron subpopulations.

Effect of vaginal electrical stimulation on female sexual functions: a randomized study

INTRODUCTION

Female sexual dysfunction (FSD) is a common problem that may be encountered in the interruption of normal sexual functioning in the sexual response cycle. Women with a pelvic floor disorder who scored low on the Female Sexual Function Index (FSFI) showed an improvement in their sexual life following treatment by vaginal electrical stimulation (VES).

AIM

The aim of this trial was to evaluate the effectiveness of VES in women with FSD without a predominant pelvic floor disorder or urinary incontinence.

METHODS

Forty-two women with FSD were randomly allocated to VES and placebo groups. Pelvic floor muscle (PFM) assessment and the FSFI questionnaire were performed at baseline and after the completion of sessions. VES treatment was administered using a vaginal probe. The probe was inserted, and a medium-frequency (50 Hz) alternating current was administered for a duty cycle of 5 seconds on followed by a 5-second rest.

MAIN OUTCOMES MEASURES

Primary outcome measure was the improvement in FSFI score. PFM assessments were performed according to the PERFECT scheme.

RESULTS

Total FSFI scores improved significantly in both the VES group and the control group. Results show that in the VES group, there was an improvement in total score and FSFI domains that improved including arousal, desire, orgasm, and satisfaction. Similarly, control group domains that improved were desire, arousal, and orgasm. But there was no significant increase in satisfaction scores in the placebo group. No significant changes in pain or lubrication domains were seen in either group. Power, endurance, fast contractions, and repetitions were significantly improved in the VES group.

CONCLUSIONS

The lack of significant differences between the placebo and VES groups, except the satisfaction domain, puts into question the effectiveness of electrical stimulation as a monotherapy in treating primary FSD without pelvic floor disorder.

Hypoactive sexual desire disorder in women: treatment options beyond testosterone and approaches to communicating with patients on sexual health

Hypoactive sexual desire disorder (HSDD) affects nearly 1 in 10 women. Thus, it is essential for pharmacists and other health care providers to be comfortable when discussing a patient's sexual health to ensure appropriate triage so that the specific causes of HSDD can be identified and potential recommendations provided. HSDD is defined as the absence or deficiency of sexual interest and/or desire, leading to significant distress and interpersonal difficulties. As health care providers, pharmacists have a critical role in assessing the presence of HSDD and providing education on available treatment options. This article will review the potential causes of HSDD and low sexual desire, the screening tools available, and the significant role of health care professionals in communicating with patients about their sexual health. An overview of the importance of behavioral modifications, the current pharmacologic options being investigated, and the use of complementary and alternative therapies will also be explored. Currently, buproprion is the primary pharmacologic agent that has shown positive results in treating patients with HSDD. The use of testosterone therapy will not be addressed in this article, as this therapy is described in greater detail elsewhere.

Pharmacologic therapy for female sexual dysfunction

Female sexual dysfunction (FSD) is a common health issue that can have significant negative effects on overall well-being and quality of life. The primary purpose of this article is to review commonly noted pharmacologic therapies for FSD. The pathophysiology, clinical evaluation, and selected nonpharmacologic therapies are also briefly addressed as well as recommendations for practice.

Flibanserin treatment increases appetitive sexual motivation in the female rat

INTRODUCTION

Flibanserin is a mixed 5-HT1A agonist/5-HT2A antagonist that has been developed for the treatment of hypoactive sexual desire disorder in women.

AIM

To assess the acute and chronic dose-response effects of flibanserin on measures of sexual desire and copulation in ovariectomized rats primed with estradiol benzoate (EB) alone or in combination with progesterone (P).

METHODS

In Experiment 1, sexually experienced ovariectomized (OVX) rats at one testing site were rendered fully sexually receptive with EB + P priming and tested weekly with a sexually active male in bi-level pacing chambers following daily flibanserin treatment for 28 days. In Experiment 2, sexually experienced OVX rats at a different testing site received EB alone and were tested weekly with sexually active males following daily flibanserin treatment.

MAIN OUTCOME MEASURES

Female appetitive behaviors (solicitations, hops and darts, anogenital investigations), defensive behaviors, pacing, lordosis, and male copulatory responses (intromissions and ejaculations) were measured during each 30-minute copulation test.

RESULTS

Acute flibanserin or 1 week of chronic flibanserin treatment did not modify sexual responses in fully (EB + P) or partially (EB-alone) primed females. After 2 weeks of chronic treatment, fully primed females displayed significantly more solicitations than the three other groups. After 3 weeks of chronic treatment, a significant increase in female solicitations was observed in both hormone-treatment groups.

CONCLUSION

This study shows the first evidence that chronic, but not acute, flibanserin treatment augments appetitive sexual behaviors in OVX female rats primed with EB + P or EB alone. Given the positive effect of flibanserin in clinical trials, these results confirm previous reports that solicitations in the female rat are a predictive animal model of human female sexual desire.

An update on the pharmacological management of female sexual dysfunction

INTRODUCTION

Female sexual dysfunction (FSD) is a global health issue, with as many as 12% of women over 18 years old reporting sexual difficulties associated with distress. It is a multifaceted problem with psychological and biological causes. Affected women tend to have an impaired quality of life, a decreased level of well-being and relationship issues. Hence there is a need for management options for affected women.

AREAS COVERED

This paper focuses on current pharmacological options for the treatment of FSD, particularly estrogens and androgens, which have been extensively studied. Some investigational drugs are also described, including the centrally acting agents such as flibanserin and bupropion, and intravaginal DHEA and testosterone, which may be useful as an alternative for women with specific conditions, such as breast cancer survivors.

EXPERT OPINION

Although approval for the use of testosterone for treatment of FSD is limited to some European countries and restricted to surgically menopausal women, there is extensive off-label use for this purpose. No other product has yet achieved regulatory approval for treatment of FSD. Completion of studies of nonhormonal FSD therapies and safety studies of testosterone may result in regulatory approval of such products for the treatment of FSD in the near future.

Efficacy of psychosocial interventions in men and women with sexual dysfunctions--a systematic review of controlled clinical trials: part 2--the efficacy of psychosocial interventions for female sexual dysfunction

INTRODUCTION

As yet, a summary of the research evidence concerning the efficacy of psychological treatment in female sexual dysfunction is lacking. Previous reviews were often nonsystematic or explored one specific sexual dysfunction.

AIM

Our systematic review provides an overview of the efficacy of psychosocial interventions in all female sexual dysfunction.

MAIN OUTCOME MEASURES

Main outcome measures included for example psychometrically validated scales, diary notes, interviews, and vulvar algesiometer. The efficacy of psychosocial interventions was measured for example by the frequency of and satisfaction with sexual activity and sexual functioning. Safety and acceptance were evaluated on the basis of adverse events and dropout rates.

METHODS

The systematic literature search included electronic database search, handsearch, contact with experts, and an ancestry approach. Studies were included if the woman was given a formal diagnosis of a sexual dysfunction (International Statistical Classification of Diseases and Related Health Problems-ICD10/-9; Diagnostic and Statistical Manual of Mental Disorders-IV/-III-R) and when the intervention was psychosocial or psychotherapeutic. The control group included either another treatment or a waiting-list control group. The report of relevant outcomes was necessary for inclusion as well as the design of the study (randomized, controlled trials [RCTs] and controlled clinical trials). The assessment of methodological quality comprised aspects of randomization, blinding, incomplete outcome data, selective reporting, and allegiance.

RESULTS

We identified 15 RCTs that investigated efficacy in female sexual dysfunction and two further studies that examined male and female sexual dysfunction together. Most trials explored sexual pain disorders. About half of all studies in women used either a concept derived from Masters and Johnson or a cognitive-behavioral treatment program. Both approaches showed significant improvements compared with a control group. Benefit was not always maintained over the (variable) follow-up period.

CONCLUSIONS

Traditional sexual therapeutic concepts proved to be efficacious in the treatment of female sexual dysfunction. A shortcoming was the rather low methodological quality of included studies.

Future sexual medicine physiological treatment targets

INTRODUCTION

Sexual function in men and women incorporates physiologic processes and regulation of the central and peripheral nervous systems, the vascular system, and the endocrine system. There is need for state-of-the-art information as there is an evolving research understanding of the underlying molecular biological factors and mechanisms governing sexual physiologic functions.

AIM

To develop an evidence-based, state-of-the-art consensus report on the current knowledge of the major cellular and molecular targets of biologic systems responsible for sexual physiologic function.

METHODS

State-of-the-art knowledge representing the opinions of seven experts from four countries was developed in a consensus process over a 2-year period.

MAIN OUTCOME MEASURES

Expert opinion was based on the grading of evidence-based medical literature, widespread internal committee discussion, public presentation, and debate.

RESULTS

Scientific investigation in this field is needed to increase knowledge and foster development of the future line of treatments for all forms of biological-based sexual dysfunction. This article addresses the current knowledge of the major cellular and molecular targets of biological systems responsible for sexual physiologic function. Future treatment targets include growth factor therapy, gene therapy, stem and cell-based therapies, and regenerative medicine.

CONCLUSIONS

Scientific discovery is critically important for developing new and increasingly effective treatments in sexual medicine. Broad physiologic directions should be vigorously explored and considered for future management of sexual disorders.

Low sexual desire--is it all in her head? Pathophysiology, diagnosis, and treatment of hypoactive sexual desire disorder

Hypoactive sexual desire disorder (HSDD) is thought to be the most prevalent form of female sexual dysfunction (FSD), affecting up to 1 in 10 US women. Hypoactive sexual desire disorder is defined by the Diagnostic and Statistical Manual of Mental Disorders, Fourth Edition, Text Revision (DSM-IV-TR) as persistent or recurrent deficiency or absence of sexual fantasies and thoughts, and/or desire for, or receptivity to, sexual activity, which causes personal distress or interpersonal difficulties and is not caused by a medical condition or drug. This definition has recently received criticism and recommendations for changes encompass the inclusion of duration, intensity, and frequency, and the elimination of distress as a diagnostic criterion. More recently, it has been suggested that arousal and desire be combined into one disorder for the upcoming DSM-V. Causes of low desire include chronic medical conditions, medications, surgeries, and psychosocial factors, but not necessarily increased age; both pre- and postmenopausal women can have HSDD, although the frequency appears to vary by age. Sexual function requires the complex interaction of multiple neurotransmitters and hormones, both centrally and peripherally, and sexual desire is considered the result of a complex balance between inhibitory and excitatory pathways in the brain. For example, dopamine, estrogen, progesterone, and testosterone play an excitatory role, whereas serotonin and prolactin are inhibitory. Thus, decreased sexual desire could be due to a reduced level of excitatory activity, an increased level of inhibitory activity, or both. A number of validated self-report and clinician-administered instruments are available for assessing female sexual function; however, most have been used primarily in clinical research trials. The Decreased Sexual Desire Screener (DSDS) was developed for practicing clinicians who are neither trained nor specialized in FSD to assist in making an accurate diagnosis of generalized acquired HSDD. As our understanding of the pathophysiology of HSDD increases, it may become easier for physicians to identify and treat women with low sexual desire.

Dopamine and oxytocin interactions underlying behaviors: potential contributions to behavioral disorders

Dopamine is an important neuromodulator that exerts widespread effects on the central nervous system (CNS) function. Disruption in dopaminergic neurotransmission can have profound effects on mood and behavior and as such is known to be implicated in various neuropsychiatric behavioral disorders including autism and depression. The subsequent effects on other neurocircuitries due to dysregulated dopamine function have yet to be fully explored. Due to the marked social deficits observed in psychiatric patients, the neuropeptide, oxytocin is emerging as one particular neural substrate that may be influenced by the altered dopamine levels subserving neuropathologic-related behavioral diseases. Oxytocin has a substantial role in social attachment, affiliation and sexual behavior. More recently, it has emerged that disturbances in peripheral and central oxytocin levels have been detected in some patients with dopamine-dependent disorders. Thus, oxytocin is proposed to be a key neural substrate that interacts with central dopamine systems. In addition to psychosocial improvement, oxytocin has recently been implicated in mediating mesolimbic dopamine pathways during drug addiction and withdrawal. This bi-directional role of dopamine has also been implicated during some components of sexual behavior. This review will discuss evidence for the existence dopamine/oxytocin positive interaction in social behavioral paradigms and associated disorders such as sexual dysfunction, autism, addiction, anorexia/bulimia, and depression. Preliminary findings suggest that whilst further rigorous testing has to be conducted to establish a dopamine/oxytocin link in human disorders, animal models seem to indicate the existence of broad and integrated brain circuits where dopamine and oxytocin interactions at least in part mediate socio-affiliative behaviors. A profound disruption to these pathways is likely to underpin associated behavioral disorders. Central oxytocin pathways may serve as a potential therapeutic target to improve mood and socio-affiliative behaviors in patients with profound social deficits and/or drug addiction.

Neuroendocrine regulation of feminine sexual behavior: lessons from rodent models and thoughts about humans

Much has been learned concerning the neuroendocrine processes and cellular mechanisms by which steroid hormones influence reproductive behaviors in rodents and other animals. In this review, a short discussion of hormones and feminine sexual behavior in some rodent species is followed by an outline of the main principles that have been learned from these studies. Examples are given of the importance of considering the timing of hormone treatments, dosage of hormone, use of a specific hormone, particular class of hormones, or form of hormone, interactions between hormones, route of administration, peripheral factors that influence hormonal response, and the possible mechanisms of action by which hormones and other factors influence sexual behaviors. Although cellular studies in humans are presently impossible to perform, mechanistic studies in rodents may provide clues about the neuroendocrine mechanisms by which hormones act and interact in the brain to influence behavior in all species, including humans.

Targeting melanocortin receptors: an approach to treat weight disorders and sexual dysfunction

The melanocortin system has multifaceted roles in the control of body weight homeostasis, sexual behaviour and autonomic functions, and so targeting this pathway has immense promise for drug discovery across multiple therapeutic areas. In this Review, we first outline the physiological roles of the melanocortin system, then discuss the potential of targeting melanocortin receptors by using MC3 and MC4 agonists for treating weight disorders and sexual dysfunction, and MC4 antagonists to treat anorectic and cachectic conditions. Given the complexity of the melanocortin system, we also highlight the challenges and opportunities for future drug discovery in this area.

RETRACTED: Evaluation of the safety and efficacy of bremelanotide, a melanocortin receptor agonist, in female subjects with arousal disorder: a double-blind placebo-controlled, fixed dose, randomized study

This article has been retracted: please see Elsevier Policy on Article Withdrawal (https://www.elsevier.com/about/our-business/policies/article-withdrawal). This article has been retracted at the request of the Editor-in-Chief. Following the retraction of Dr. Safarinejad's work by other journals, The Journal of Sexual Medicine has undertaken an extensive re-review of all papers Dr. Safarinejad published with the journal. Following an intensive re-evaluation and close scrutiny of the manuscripts, our expert reviewers raised multiple concerning questions about the methodology, results, and statistical interpretation as presented in this article. Dr. Safarinejad was contacted to provide his original data and offer explanations to address the concerns expressed by the reviewers. Dr Safarinejad chose not to respond. Consequently, we can no longer verify the results or methods as presented and therefore retract the article.