Effects of opioid blockade with nalmefene in older impotent men

Opioid-Induced Sexual Dysfunction in Cancer Patients

Simple Summary

Sexual disorders affect up to 80% of cancer patients, depending on the type of cancer, yet they are commonly overlooked and untreated. Opioid-induced sexual dysfunction (OISD) is reported in half of opioid users. The pathophysiology of OISD—still a subject for research—may include disorders of both the endocrine and nervous systems, expressed in, among other things, erectile dysfunction and declined sexual desire, sexual arousal, orgasm, and general satisfaction with one’s sex life. The etiology of sexual dysfunction in cancer patients is usually multifactorial, so the management should be multifaceted and individualized by targeting pathophysiological factors. The treatment options for OISD are few and include testosterone replacement therapy, bupropion, opioid antagonists, phosphodiesterase type 5 inhibitors, plant-derived substances, and non-pharmacological treatments, although the evidence is insufficient. One of the treatment options may also be a choice of an opioid that is less likely to cause sexual dysfunction, yet further research is necessary.

Abstract

Sexual dysfunction is common in patients with advanced cancer, although it is frequently belittled, and thus consistently underdiagnosed and untreated. Opioid analgesics remain fundamental and are widely used in cancer pain treatment. However, they affect sexual functions primarily due to their action on the hypothalamus–pituitary–gonadal axis. Other mechanisms such as the impact on the central and peripheral nervous systems are also possible. The opioid-induced sexual dysfunction includes erectile dysfunction, lack of desire and arousal, orgasmic disorder, and lowered overall sexual satisfaction. Around half of the individuals taking opioids chronically may be affected by sexual dysfunction. The relative risk of sexual dysfunction in patients on chronic opioid therapy and opioid addicts increased two-fold in a large meta-analysis. Opioids differ in their potential to induce sexual dysfunctions. Partial agonists and short-acting opioids may likely cause sexual dysfunction to a lesser extent. Few pharmaceutical therapies proved effective: testosterone replacement therapy, PDE5 inhibitors, bupropion, trazodone, opioid antagonists, and plant-derived medicines such as Rosa damascena and ginseng. Non-pharmacological options, such as psychosexual or physical therapies, should also be considered. However, the evidence is scarce and projected primarily from non-cancer populations, including opioid addicts. Further research is necessary to explore the problem of sexuality in cancer patients and the role of opioids in inducing sexual dysfunction.

Association Between Opioid Use and Risk of Erectile Dysfunction: A Systematic Review and Meta-Analysis

BACKGROUND

Opioid analgesics have been widely used to relieve chronic pain conditions; however, a connection between opioid analgesic administration and increased susceptibility to erectile dysfunction (ED) has been hypothesized.

AIM

To evaluate whether opioid use was a risk factor for ED in a systematic review and meta-analysis.

METHODS

The PubMed, Cochrane Library, and Embase databases were searched to identify eligible studies concerning opioid use and risk of ED from inception to April 2017. The association between opioid use and risk of ED was summarized using the relative risk with 95% CI. Sensitivity analyses were conducted to assess potential bias. The Begg and Egger tests were used for publication bias analysis. The GRADE evidence profile tool was used to assess the quality of the evidence.

OUTCOMES

The overall combined risk estimates for the effect of opioid use on ED were calculated using a random-effects model.

RESULTS

This meta-analysis included 8,829 men (mean age = 41.6 years) from 10 studies, 2,456 of whom received opioid management (duration of intervention = 4 months to 9.5 years). Pooled results demonstrated that the use of opioids was significantly associated with an increased risk of ED (relative risk = 1.96, 95% CI = 1.66-2.32, P < .001). Estimates of the total effects were generally consistent in the sensitivity analysis. No evidence of publication bias was observed. The overall quality of evidence was rated as low.

CLINICAL IMPLICATIONS

We found that men with opioid use had a significantly increased prevalence of ED, which suggests that patients and clinicians should be aware of the potential role played by opioid administration in the development of ED.

STRENGTHS AND LIMITATIONS

This is the first meta-analysis performed to describe the relation between opioid use and ED risk based on all available epidemiologic studies. However, the direction of causality between opioid use and risk of ED should be interpreted with caution because most included studies used a cross-sectional design.

CONCLUSION

Evidence from the included observational studies indicated that men with opioid use had a significantly increased risk of ED. Further randomized controlled trials are still needed to confirm this relation. Zhao S, Deng T, Luo L, et al. Association Between Opioid Use and Risk of Erectile Dysfunction: A Systematic Review and Meta-Analysis. J Sex Med 2017;14:1209-1219.

Mechanisms of penile erection and basis for pharmacological treatment of erectile dysfunction

Erection is basically a spinal reflex that can be initiated by recruitment of penile afferents, both autonomic and somatic, and supraspinal influences from visual, olfactory, and imaginary stimuli. Several central transmitters are involved in the erectile control. Dopamine, acetylcholine, nitric oxide (NO), and peptides, such as oxytocin and adrenocorticotropin/α-melanocyte-stimulating hormone, have a facilitatory role, whereas serotonin may be either facilitatory or inhibitory, and enkephalins are inhibitory. The balance between contractant and relaxant factors controls the degree of contraction of the smooth muscle of the corpora cavernosa (CC) and determines the functional state of the penis. Noradrenaline contracts both CC and penile vessels via stimulation of α₁-adrenoceptors. Neurogenic NO is considered the most important factor for relaxation of penile vessels and CC. The role of other mediators, released from nerves or endothelium, has not been definitely established. Erectile dysfunction (ED), defined as the "inability to achieve or maintain an erection adequate for sexual satisfaction," may have multiple causes and can be classified as psychogenic, vasculogenic or organic, neurologic, and endocrinologic. Many patients with ED respond well to the pharmacological treatments that are currently available, but there are still groups of patients in whom the response is unsatisfactory. The drugs used are able to substitute, partially or completely, the malfunctioning endogenous mechanisms that control penile erection. Most drugs have a direct action on penile tissue facilitating penile smooth muscle relaxation, including oral phosphodiesterase inhibitors and intracavernosal injections of prostaglandin E₁. Irrespective of the underlying cause, these drugs are effective in the majority of cases. Drugs with a central site of action have so far not been very successful. There is a need for therapeutic alternatives. This requires identification of new therapeutic targets and design of new approaches. Research in the field is expanding, and several promising new targets for future drugs have been identified.

Anatomy, physiology, and pathophysiology of erectile dysfunction

INTRODUCTION

Significant scientific advances during the past 3 decades have deepened our understanding of the physiology and pathophysiology of penile erection. A critical evaluation of the current state of knowledge is essential to provide perspective for future research and development of new therapies.

AIM

To develop an evidence-based, state-of-the-art consensus report on the anatomy, physiology, and pathophysiology of erectile dysfunction (ED).

METHODS

Consensus process over a period of 16 months, representing the opinions of 12 experts from seven countries.

MAIN OUTCOME MEASURE

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

RESULTS

ED occurs from multifaceted, complex mechanisms that can involve disruptions in neural, vascular, and hormonal signaling. Research on central neural regulation of penile erection is progressing rapidly with the identification of key neurotransmitters and the association of neural structures with both spinal and supraspinal pathways that regulate sexual function. In parallel to advances in cardiovascular physiology, the most extensive efforts in the physiology of penile erection have focused on elucidating mechanisms that regulate the functions of the endothelium and vascular smooth muscle of the corpus cavernosum. Major health concerns such as atherosclerosis, hyperlipidemia, hypertension, diabetes, and metabolic syndrome (MetS) have become well integrated into the investigation of ED.

CONCLUSIONS

Despite the efficacy of current therapies, they remain insufficient to address growing patient populations, such as those with diabetes and MetS. In addition, increasing awareness of the adverse side effects of commonly prescribed medications on sexual function provides a rationale for developing new treatment strategies that minimize the likelihood of causing sexual dysfunction. Many basic questions with regard to erectile function remain unanswered and further laboratory and clinical studies are necessary.

Age-related changes in the oestrous cycle and reproductive hormones in senescence-accelerated mouse

To investigate age-related changes in the oestrous cycle and reproductive hormone levels in senescence-accelerated mouse (SAM), we examined these parameters in 3-, 5-, 7-, 9- and 11-month-old female SAM-prone/8 (SAMP8) and SAM-resistant/1 (SAMR1) strains. Levels of beta-endorphin (beta-EP) and substance P (SP) in the hypothalamus were also measured. The oestrous cycle and dioestrus of 9-month-old SAMP8 mice were significantly prolonged compared with age-matched SAMR1 mice. Furthermore, the concentration of serum oestradiol was lower and the level of pituitary luteinising hormone was higher in SAMP8 mice compared with SAMR1 mice. This characterises the hypothalamus-pituitary-ovary (HPO) axis of the SAMP8 strain as hypergonadotropic-hypogonad. The levels of beta-EP and SP in the SAMP8 hypothalamus were lower than in the SAMR1 hypothalamus. These results indicate that the function of the HPO axis in SAMP8 mice declines early and this may be attributed, in part, to the decline in beta-EP and SP concentrations in the hypothalamus.

Pharmacotherapy for Erectile Dysfunction

INTRODUCTION

Advances in understanding of the biochemistry and physiology of penile erection have led to breakthroughs in pharmacotherapy of erectile dysfunction.

AIM

To provide recommendations/guidelines concerning state-of-the-art knowledge for the putative molecular and cellular mechanisms of action of centrally and peripherally acting drugs currently utilized in pharmacotherapy of erectile dysfunction.

METHODS

An international consultation in collaboration with the major urology and sexual medicine associations assembled over 200 multidisciplinary experts from 60 countries into 17 committees. Committee members established specific objectives and scopes for various male and female sexual medicine topics. The recommendations concerning state-of-the-art knowledge in the respective sexual medicine topic represent the opinion of experts from five continents developed in a process over a two-year period. Concerning the Pharmacotherapy for Erectile Dysfunction Committee there were 25 experts from 10 countries.

MAIN OUTCOME MEASURE

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

RESULTS

Selective and potent oral PDE5 inhibitors have significantly more affinity than cGMP and form broader molecular interactions with multiple amino acids, thereby blocking access to cGMP in the catalytic sites of the PDE5 enzyme. PDE5 inhibitors, which vary as to biochemical potency, selectivity and pharmacokinetics, lead to cGMP elevation and relaxation facilitation of penile corpus cavernosum smooth muscle cells following sexual stimulation. Various centrally acting drugs influence sexual behaviour. In particular, the dopaminergic substance apomorphine is a central enhancer that acts in the paraventricular nucleus of the hypothalamus as a dopamine (D2) receptor agonist, induces and increases penile erection responses via disinhibition, following sexual stimulation.

CONCLUSIONS

There is a need for more research in the pharmacotherapeutic development of central and peripheral agents for safe and effective erectile dysfunction treatment.

Andropause:

There is increasing evidence that the common condition of hypogonadism in older men when associated with symptoms responds well to testosterone replacement. Over the last few years there has been a marked increase in the awareness and treatment of the andropause [137]. Long-term side effects of testosterone are uncertain with only eight people over 50 years having been studied for 10 years [138]. Testosterone needs to be considered a quality-of-life drug, similar to sildenafil, and at present it should be used only if it produces symptomatic improvement. There is a need for a men's health study to determine the long-term efficacy and safety of testosterone replacement in older persons.

Androgens and aging

This review supports the conclusion that the use of testosterone replacement therapy for the treatment of the symptoms of androgen deficiency in aging males (ADAM) may be appropriate if undertaken with due caution. The best safety data exists for using oral therapy with testosterone undeconoate. Less data exists for the treatment of postmenopausal women with testosterone. Tibolone (an estrogen--prostagen--testosterone) compound, may make the need for testosterone being added to estrogen in women unnecessary. Less data is available to support the use of DHEA or its sulfate or pregnenolone. Further studies are clearly necessary in all these areas. However, it may be tentatively concluded that we are at the dawning of the age of androgens.

Acute effects of nalmefene on LH, prolactin, and testosterone in male rhesus monkeys

The effects of the long-acting opioid antagonist, nalmefene [17-N-cyclopropylmethyl-3,14-beta-dihydroxy-4, 5-alpha-epoxy-6-methylene morphinan hydrochloride] on LH, T, and prolactin release in rhesus monkeys are unknown. The acute effects of nalmefene (0.01 and 0.10 mg/kg, IV) or placebo on LH, PRL, and T were studied, and samples were collected at 10-min intervals for 360 min to permit cluster analysis of pulsatile release patterns. LH increased significantly within 30 min after nalmefene, and remained significantly above baseline levels for 50 to 60 min (p < 0.05). Testosterone increased significantly within 70 to 80 min after nalmefene, and remained significantly above baseline for 60 min (p < 0.05). Although nalmefene antagonizes opioid agonists for 6-8 h, inhibitory feedback by testosterone appeared to limit the duration of its antagonism of endogenous opioid inhibition of LHRH and stimulation of LH. Nalmefene did not change LH or PRL pulse frequency or amplitude significantly in comparison to placebo administration.

Androgen deficiency in aging men

The authors cover many topics, including hypothalamic-pituitary-testicular axis and aging, sexuality, muscle strength, Leptin, osteoporosis, etc. They examine the ADAM Questionnaire and develop six conclusions regarding older men and testosterone.

Geriatric cachexia: the role of cytokines

Weight loss in elderly patients is a common clinical problem. Wasting and cachexia are associated with severe physiologic, psychologic, and immunologic consequences, regardless of the underlying causes. Cachexia has been associated with infections, decubitus ulcers, and even death. Multivariate analyses of risk and prognostic factors in community-acquired pneumonia in the elderly have found that age by itself is not a significant factor related to prognosis. Among the significant risk factors, only nutritional status is amenable to medical intervention. Cachexia in the elderly may have profound consequences: medical, cognitive, and psychiatric disorders may diminish self-reliance in activities of daily living, thus reducing quality of life and increasing the frequency of secondary procedures, hospitalizations, and the need for skilled care. Cachexia is associated with higher-than-normal concentrations of tumor necrosis factor alpha (TNF-alpha), interleukin (IL) 1, IL-6, serotonin, and interferon gamma. The role of these proinflammatory cytokines has been established in the cachexia seen in cancer and AIDS patients. Reduction in the concentrations of these cytokines is associated with weight gain. Drugs that promote appetite stimulation and weight gain, such as progestational agents, cyproheptadines, pentoxifylline, and thalidomide may work by down-regulating these proinflammatory cytokines. An understanding of the relation between cachexia and negative regulatory cytokines may point to effective treatment of geriatric cachexia as well.

Trophic factors in aging. Should older people receive hormonal replacement therapy?

The aging process is associated with significant declines in the levels of many hormones and trophic factors including estrogen, testosterone, growth hormone (somatropin, somatotropin) and insulin-like growth factor-1 (IGF-1, somatomedin-1, somatomedin-C). Since the classic age-related changes resemble the signs and symptoms of endocrine deficiency, it has been hypothesised that some of the negative effects of aging are due to these hormonal deficits. Consequently, the potential role of hormonal replacement in reversing the deleterious effects of aging deserves investigation. In old hypogonadal men, preliminary studies have shown that testosterone replacement not only improves libido but also significantly increases musculoskeletal mass and strength. However, adverse effects have included increases in haematocrit and prostate specific antigen. Similarly, short term studies with growth hormone replacement have shown substantial bodyweight gain, particularly in severely malnourished older adults, but longer studies have been limited by adverse effects such as gynaecomastia and carpal tunnel syndrome in a few people. Thus, though both testosterone and growth hormone may have potential roles for frailty syndromes in the elderly, long term clinical trials are needed to confirm these positive effects and assess their safety. On the other hand, the multiple beneficial effects of estrogen replacement in older women such as relieving acute menopausal symptoms and preventing postmenopausal osteoporosis are well recognised. Observational studies also suggest that estrogen may decrease cardiovascular disease. However, the optimum duration of treatment and the best way to administer this hormone are still unknown. Also, estrogen may be less effective in senile osteoporosis which primarily results from age-related bone loss. Traditionally, age-related bone loss has been attributed to impaired vitamin D activation and decreased calcium absorption. Thus, it was thought that such bone losses may be ameliorated by calcium supplementation. However, recent studies suggest that alterations in local factors affecting bone cell function may also be important in the pathogenesis of osteoporosis. An increase in potent bone resorbing factors, such as the cytokines interleukin-1 and interleukin-6, has been recently demonstrated in elderly patients with osteoporosis. In these patients, it has been suggested that there may also be a decrease in bone growth factors such as IGF-1 and transforming growth factor-beta. Accordingly, studies are underway to determine whether these factors may be useful in the prevention of osteoporosis. Other growth factors recently identified which may be important in aging include epidermal growth factor, nerve growth factor and fibroblast growth factor.(ABSTRACT TRUNCATED AT 400 WORDS)

Management of impotence. Diagnostic considerations and therapeutic options

Impotence affects an estimated 10 million American men. The cause is usually organic in men over age 50; psychogenic impotence is more common in younger men. Vascular disease is the most common cause of impotence. Evaluation in patients with impotence includes thorough history taking and diagnostic testing. Once the cause of impotence is determined, appropriate management can be chosen. Current therapeutic options include vacuum tumescence devices, self-injection, oral therapy, psychotherapy, and penile prostheses.