Understanding the Role of Serotonin in Female Hypoactive Sexual Desire Disorder and Treatment Options

Advances in drug design and therapeutic potential of selective or multitarget 5-HT1A receptor ligands

5-HT1A receptor (5-HT1A-R) is a serotoninergic G-protein coupled receptor subtype which contributes to several physiological processes in both central nervous system and periphery. Despite being the first 5-HT-R identified, cloned and studied, it still represents a very attractive target in drug discovery and continues to be the focus of a myriad of drug discovery campaigns due to its involvement in numerous neuropsychiatric disorders. The structure-activity relationship studies (SAR) performed over the last years have been devoted to three main goals: (i) design and synthesis of 5-HT1A-R selective/preferential ligands; (ii) identification of 5-HT1A-R biased agonists, differentiating pre- versus post-synaptic agonism and signaling cellular mechanisms; (iii) development of multitarget compounds endowed with well-defined poly-pharmacological profiles targeting 5-HT1A-R along with other serotonin receptors, serotonin transporter (SERT), D2-like receptors and/or enzymes, such as acetylcholinesterase and phosphodiesterase, as a promising strategy for the management of complex psychiatric and neurodegenerative disorders. In this review, medicinal chemistry aspects of ligands acting as selective/preferential or multitarget 5-HT1A-R agonists and antagonists belonging to different chemotypes and developed in the last 7 years (2017-2023) have been discussed. The development of chemical and pharmacological 5-HT1A-R tools for molecular imaging have also been described. Finally, the pharmacological interest of 5-HT1A-R and the therapeutic potential of ligands targeting this receptor have been considered.

Effect of folic acid on the sexual function of postmenopausal women: a triple-blind randomized controlled trial

BACKGROUND

There are reports of sexual dysfunction in postmenopausal women, and several treatment recommendations are available.

AIM

To investigate the effect of folic acid on postmenopausal women's sexual function.

METHODS

This triple-blind randomized controlled trial was conducted in Tehran, Iran, in 2020. A sample of 100 postmenopausal women was recruited from comprehensive health centers affiliated with the Shahid Beheshti University of Medical Sciences. Eligible women were randomly assigned to receive folic acid (5 mg) or placebo on an empty stomach every day for 8 weeks. Women were assessed at 3 time points: baseline and 4 and 8 weeks after the intervention.

OUTCOME

Sexual function was the main outcome, as measured by the Female Sexual Function Index.

RESULTS

The mean ± SD age of participants in the folic acid and placebo groups was 53.2 ± 3.84 and 54.4 ± 4.05 years, respectively (P = .609). The results obtained from mixed effects analysis of variance revealed a statistically significant difference between baseline and posttreatment scores and the interaction between time and group for desire, orgasm, satisfaction, arousal, pain, and total sexual function score, with the folic acid group improving more than control group. Lubrication was the only domain that showed no significant difference for the interaction between time and group.

CLINICAL IMPLICATIONS

Folic acid may beneficially affect sexual function in postmenopausal women.

STRENGTHS AND LIMITATIONS

Strengths include the novelty of the subject, the triple-blind design, the block randomization, the administration of a standard scale for sexual function (Female Sexual Function Index), and the affordability and availability of folic acid. This study was conducted with a small sample size and short follow-up time; therefore, interpretation of the results requires great caution.

CONCLUSION

The findings suggest that folic acid possibly improves sexual function in postmenopausal women. Larger studies are needed to confirm the findings.

TRIAL REGISTRATION

IRCT20150128020854N8; August 2, 2020. Iranian Registry of Clinical Trials; https://en.irct.ir/user/trial/48920/view.

Sexual health and serotonin 4 receptor brain binding in unmedicated patients with depression-a NeuroPharm study

Sexual dysfunction is prominent in Major Depressive Disorder (MDD) and affects women with depression more than men. Patients with MDD relative to healthy controls have lower brain levels of the serotonin 4 receptor (5-HT₄R), which is expressed with high density in the striatum, i.e. a key hub of the reward system. Reduced sexual desire is putatively related to disturbed reward processing and may index anhedonia in MDD. Here, we aim to illuminate plausible underlying neurobiology of sexual dysfunction in unmedicated patients with MDD. We map associations between 5-HT₄R binding, as imaged with [¹¹C]SB207145 PET, in the striatum, and self-reported sexual function. We also evaluate if pre-treatment sexual desire score predicts 8-week treatment outcome in women. From the NeuroPharm study, we include 85 untreated MDD patients (71% women) who underwent eight weeks of antidepressant drug treatment. In the mixed sex group, we find no difference in 5-HT₄R binding between patients with sexual dysfunction vs normal sexual function. However, in women we find lower 5-HT₄R binding in the sexual dysfunctional group compared to women with normal sexual function (β = -0.36, 95%CI[-0.62:-0.09], p = 0.009) as well as a positive association between sexual desire and 5-HT₄R binding (β = 0.07, 95%CI [0.02:0.13], p = 0.012). Sexual desire at baseline do not predict treatment outcome (ROC curve AUC = 52%[36%:67%]) in women. Taken together, we find evidence for a positive association between sexual desire and striatal 5-HT₄R availability in women with depression. Interestingly, this raises the question if direct 5-HT₄R agonism can target reduced sexual desire or anhedonia in MDD.

Pharmacotherapy for female sexual dysfunctions (FSDs): what is on the market and where is this field heading?

INTRODUCTION

Female sexual dysfunctions (FSDs) are common in women of any age and have a huge impact on quality of life and relationships. They have a multifaceted etiology limiting the development of pharmacotherapies with a high rate of effectiveness. Safety issues are also a concern.

AREAS COVERED

The authors report the most recent advances in pharmacotherapy for premenopausal and postmenopausal women with a main focus on hypoactive sexual desire disorders (HSDD) and associated sexual symptoms. Good levels of evidence have emerged for psychoactive agents, such as flibanserin and bremelanotide, as well as hormonal compounds (transdermal testosterone). The authors also report briefly on intravaginal DHEA (prasterone), local estrogen therapy (LET), and ospemifene to manage effectively vulvovaginal atrophy/genitourinary syndrome of menopause (VVA/GSM). In addition, they discuss promising therapeutic options highlighting the main reasons that hamper the availability of new labeled products. Finally, they include the importance of the multimodal approach to address FSDs.

EXPERT OPINION

Approved pharmacotherapies for FSD are limited. Validated multidimensional instruments and adequate objective measures of physical and mental responses to sexual external and internal incentives are mandatory to identify women suitable to chronic or on-demand treatments and to assess their pattern of response in research and practice.

The pathophysiology of sexual dysfunction in Parkinson's disease: An overview

Sexual dysfunction is a common, poorly recognized, poorly discussed (often because of cultural perceptions and sensitivities), bothersome and neglected aspect of the range of non-motor symptoms of Parkinson's disease (PD). The spectrum of sexual dysfunction in PD ranges from hyposexuality-based disturbances to hypersexuality-dominated behaviors in the context of drug-induced impulse control disorder. The pathophysiological mechanisms underlying PD-related sexual dysfunction, specifically for hyposexual disorders, are thus heterogeneous and still not fully understood. However, central and peripheral neural mechanisms secondary to the hallmark pathological alterations of the disease (alpha-synuclein deposition and nigrostriatal degeneration) and to the associated network and neurotransmitter dysfunctions, together with the effects of dopaminergic therapies, seem to play an important role in the development of sexual disturbances. In this chapter, we therefore review the neuroanatomical and neurophysiological basis of sexual function in humans, and we provide insights on the pathophysiological mechanisms of hyposexuality and hypersexuality in PD.

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.

Persistent sexual dysfunction after SSRI withdrawal: a scoping review and presentation of 86 cases from the Netherlands

BACKGROUND

Sexual dysfunction is highly prevalent worldwide. A specific form is persistent sexual dysfunction after SSRI withdrawal. We conducted a systematic literature review in order to characterize factors related to post SSRI sexual dysfunction (PSSD) and analyzed spontaneous reports of persistent sexual dysfunction reported to the Netherlands Pharmacovigilance Center Lareb.

RESEARCH DESIGN AND METHODS

A systematic literature review was conducted following the PRISMA-ScR guidelines. In addition, reports of PSSD submitted to the Netherlands Pharmacovigilance Center Lareb between 1992 and 2021 were analyzed.

RESULTS

A total of 237 articles were retrieved through the search and 33 articles were selected for inclusion in this review, in accordance with the inclusion criteria. Information regarding the characteristics of the condition, its clinical management, patient characteristics, and impact of PSSD is presented. A total of 86 reports of persistent sexual dysfunction were analyzed. The longest case being a patient with PSSD for 23 years. The main symptoms were: loss or decreased libido (n = 53), erectile dysfunction (n = 23) and anorgasmia (n = 5).

CONCLUSIONS

PSSD impact includes sexual, psychological, and social consequences. Little is known about the mechanisms underlying PSSD and no effective treatment exists. It is necessary to increase recognition of PSSD among prescribers and improve its management at the clinical level.

Development and Greenness Evaluation of Spectrofluorometric Methods for Flibanserin Determination in Dosage Form and Human Urine Samples

Green, economic and sensitive two spectrofluorometric methods were developed for the quantitation of flibanserin (FB) in different matrices, which are based on FB native fluorescence properties. The first technique depends on measuring the relative fluorescence intensity of FB directly at emission and excitation wavelengths(λ_em/λ_ex) (371 nm/247 nm), while the second technique is a first derivative (D¹) spectrofluorometric method, which depends on measuring the peak amplitudes at 351 nm. Linear regressions were observed in the range of 0.1–1.5 μg/mL for both methods. Moreover, both methods were efficiently extended to analyze FB in human urine, indicating the ultra-sensitivity of the methods, and linear regression was found within a range 0.05–0.7 μg/mL for both methods. Excellent selectivity of the proposed methods and good recoveries were obtained upon the analysis of FB in pharmaceutical dosage form and human urine samples without interference from matrix components with acceptable ranges, from 98.86 to 101.46% and from 98.08 to 102.37%, respectively. Greenness of the developed methods was assessed using the national environmental method index (NEMI) and Analytical Eco-scale and Green Analytical Procedure Index (GAPI). The three approaches confirmed that the developed methods are green, safe and environment-friendly.

Hypoactive sexual desire disorder (HSDD) is not "female erectile dysfunction (ED)": challenges with the characterization of HSDD in women based on a systematic literature review

Objective: Hypoactive sexual desire disorder (HSDD) in women has been viewed inaccurately by some in the medical and payer community as analogous to erectile dysfunction (ED) in men. This literature review aims to highlight the distinctions between HSDD and ED.Methods: Two systematic literature searches were conducted on the epidemiology, symptomatology and biopsychosocial outcomes of HSDD and ED. Studies published since 2007 were considered for HSDD; studies published since 2012 were considered for ED.Results: HSDD in women is primarily a central nervous system condition related to neuroendocrine factors, whereby neural pathways that regulate sexual excitation and/or inhibition appear to be involved. A combination of organic and psychogenic factors often contributes to ED. HSDD and ED are associated with similar psychological and interpersonal consequences, but affect different phases of the sexual response model (desire versus arousal) and have different pathophysiologies, therefore requiring different treatment and outcome paradigms. ED is measured by objective, physiological responses (erection and sexual function), but quantitative assessments for HSDD are more difficult because loss of desire with associated distress has to be assessed. Outcome measures used to assess ED, such as the number of satisfying sexual events, are far less informative as an endpoint for randomized clinical trials of treatments for HSDD.Conclusions: HSDD and ED are distinct conditions affecting different phases of the sexual response model, and thus require clear and unique clinical characterization and adequate communication between the health care professional and patient for appropriate diagnosis, management and treatment.

Panic Disorder Correlates With the Risk for Sexual Dysfunction

BACKGROUND

Reports have suggested that sexual dysfunction is an underestimated complication of panic disorder, but little research has focused on sexual dysfunction associated specifically with panic disorder. The purpose of this systematic review was to investigate whether patients with panic disorder who are not currently receiving treatment had a higher risk of sexual dysfunction than healthy people, as well as to clarify the appropriate treatment for this patient group.

METHODS

Articles that reported panic disorder complicated with sexual dysfunction were identified by a systematic literature search of electronic databases, including PubMed, the Cochrane databases, EMBASE, and PsycINFO.

RESULTS

Six articles were included in the review. Patients with panic disorder showed a high prevalence of sexual aversion (35.7% to 64%) and sexual infrequency (36% to 44%). One cohort study indicated that untreated patients with panic disorders had a higher risk of erectile dysfunction than controls. Another article that focused specifically on female patients reported that the patients with panic disorder exhibited decreased frequency of sexual behavior and decreased sexual desire compared with the controls. However, 2 studies found conflicting results after adjustment for confounding factors.

CONCLUSIONS

Although the results were mixed, it appears that patients with panic disorder tended to be more susceptible to sexual dysfunction than the general population. Further trials with larger sample sizes and rigorous research designs are needed to establish the relationship between sexual dysfunction and panic disorder.

Neuroanatomy and function of human sexual behavior: A neglected or unknown issue?

INTRODUCTION

Sexual desire, arousal, and orgasm are mediated by complex, yet still not fully understood, interactions of the somatic and autonomic nervous systems operating at the central and peripheral levels. Disruption of endocrine, neural, or vascular response, caused by aging, medical illness, neurological diseases, surgery, or drugs, can lead to sexual dysfunctions, thus significantly affecting patients' quality of life.

PURPOSE

This narrative review aims at characterizing the involvement of the central nervous system in human sexual behavior.

METHODS

A literature search was conducted using PubMed in its entirety up to June 2018, analyzing the studies dealing with the neurobiological and neurophysiological basis of human sexuality.

RESULTS

Sexual behavior is regulated by both subcortical structures, such as the hypothalamus, brainstem, and spinal cord, and several cortical brain areas acting as an orchestra to finely adjust this primitive, complex, and versatile behavior. At the central level, dopaminergic and serotonergic systems appear to play a significant role in various factors of sexual response, although adrenergic, cholinergic, and other neuropeptide transmitter systems may contribute as well.

CONCLUSIONS

Providing healthcare professionals with information concerning sexual behavior may overcome useless and sometimes dangerous barriers and improve patient management, since sexual well-being is considered one of the most important aspects of one's quality of life.

Safety and Tolerability of Evening Ethanol Consumption and Bedtime Administration of Flibanserin in Healthy Premenopausal Female Subjects

Introduction

Flibanserin, a treatment for hypoactive sexual desire disorder, carries warnings for increased risk of severe hypotension and syncope when used with alcohol. However, these warnings are not informed by studies that used flibanserin’s recommended bedtime dosing because previous alcohol studies assessed flibanserin’s safety during the day.

Aim

The aim of this study was to assess the effects of ethanol in a real-world context in premenopausal women taking flibanserin at bedtime.

Methods

In a randomized, placebo-controlled, double-blind study, 24 healthy premenopausal women (mean age = 34.5 ± 9.9 years; mean body mass index = 25.2 ± 3.4 kg/m²) were dosed with flibanserin or placebo for 3 days to achieve steady-state plasma levels. In a clinical research unit, subjects (n = 22) were provided 2 units of wine (150 mL/unit; 12% ethanol content) or a nonalcoholic beverage with a standardized 3-course evening meal. Flibanserin 100 mg or placebo was administered at bedtime 2.5 hours after the end of the evening meal. On a separate day, subjects were provided the alternative beverage (± alcohol) with the same evening meal and dosed with the same treatment (flibanserin or placebo) at bedtime. After a 5-day washout period, subjects crossed over to the other treatment arm and the protocol was repeated.

Main Outcome Measure

Adverse events (AEs) and vital signs were monitored.

Results

In the absence of ethanol, headaches and hypotension were the only AEs that occurred in ≥2 subjects after flibanserin dosing (placebo corrected rates were 17.4% and 8.7%, respectively). After ethanol consumption, the rate of hypotension after flibanserin dosing was no greater than with flibanserin or placebo after nonalcoholic beverage consumption. There were no instances of orthostatic hypotension or syncope and no serious AEs or AEs leading to study discontinuation.

Conclusion

Flibanserin dosed at bedtime after moderate amounts of alcohol with an evening meal was well-tolerated with no evidence of clinically significant hypotension or syncope.

Millheiser L, Clayton AH, Parish SJ, et al. Safety and Tolerability of Evening Ethanol Consumption and Bedtime Administration of Flibanserin in Healthy Premenopausal Female Subjects. Sex Med 2019;7:418–424.