Pharmacological management of erectile dysfunction

Acute and subacute toxicity evaluation of hydroalcoholic extract from the stem bark of Bois Bande (Parinari campestris Aubl.1772) in rats

INTRODUCTION

The bark of Bois Bande (Parinari campestris) is a popular aphrodisiac in the Caribbean that has been traditionally used for many years to restore sexual vitality, increase sperm count, and treat erectile dysfunction, without valid scientific data. Acute and 28-day subacute toxicity studies were conducted to evaluate the safety of the hydroalcoholic extract of P.campestris bark and to find a safe dose for human use in conventional medicine.

METHODS

The acute toxicity study used a single oral dose of P.campestris extract at four separate doses, 5, 50, 300, and 2,000 mg/kg, and was seen for 14 days, while the subacute toxicity study used a daily oral dose of P.campestris extract at 3 different doses, 100, 300, and 1000 mg/kg/day for 28 days.

RESULTS

The LD50 of P.campestris extract was found to be greater than 2000 mg/kg in the acute toxicity study. P.campestris extract did not show toxicity at 1000 mg/kg/day in subacute toxicity trial; NOAEL was 1000 mg/kg/day in rats. However, the body weight was increased in males.

CONCLUSION

In conclusion, 1000 mg/kg P.campestris extract can be considered safe and non-toxic in males.

Toxicity Evaluation of Anacardium occidentale, the Potential Aphrodisiac Herb

Anacardium occidentale L. leaf demonstrates sexual enhancement effect. Therefore, it can be used as the potential supplement and functional ingredient. However, the ethanolic leaf extract of this plant is a modified form of traditional application and the toxicity evaluation is required. To assess cytotoxicity of the extract, RAW 264.7 cells were treated with A. occidentale leaf extract in the concentration range between 0.625 and 10 mg/mL. Our results showed that the extract showed more than 90% cell viability at the concentration of 2.5 mg/mL after 24-hour exposure. To assure the consumption safety, the acute and subchronic toxicity must be studied. Acute toxicity showed that the extract is safe even at the highest dose of 2 g/kg in both sexes of Wistar rats. No changes in behavior, physiology, gross pathology, and histology were observed. To determine the subchronic toxicity of extract, both sexes of Wistar rats were orally given the extract at doses of 20, 100, and 500 mg/kg once daily for 90 days. No changes in body weight, food, and water intake, motor coordination, behavior, and mental alertness were observed. The significant reduction of white blood cell, platelet, and cholesterol together with increase in MCHC was observed in male rats. The reductions of white blood cell and platelet together with the elevations of hemoglobin and hematocrit were also observed in female rats. However, all changes were in normal range. The current results revealed that an ethanolic extract of A. occidentale leaf was well tolerated via oral consumption up to dose of 500 mg/kg BW for 90 days and did not produce any toxicity. Our in vitro cytotoxicity test also confirmed this safety.

Exploring scientifically proven herbal aphrodisiacs

Procreation was an important moral and religious issue and aphrodisiacs were sought to ensure both male and female potency. Sexual dysfunction is an inability to achieve a normal sexual intercourse, including premature ejaculation, retrograded, retarded or inhibited ejaculation, erectile dysfunction, arousal difficulties (reduced libido), compulsive sexual behavior, orgasmic disorder, and failure of detumescence. The introduction of the first pharmacologically approved remedy for impotence, Viagra (sildenafil) in 1990s caused a wave of public attention, propelled in part by heavy advertising. The search for such substances dates back millennia. An aphrodisiac is an agent (food or drug) that arouses sexual desire. The hunt for natural supplement from medicinal plants is being intensified mainly because of its fewer side effects. In this review, we have mentioned the pharmacologically tested (either in man or animal or in both) aphrodisiac plants, which have claimed for its uses.

Comparative effects of sildenafil, phentolamine, yohimbine and l-arginine on the rabbit corpus cavernosum

Penile erection involves relaxation of smooth muscle of corpus cavernosum and associated arterioles. Sildenafil, a highly selective inhibitor of phosphodiesterase type 5, is effective in the treatment of erectile dysfunction. The aim of this study is to investigate the effect of sildenafil on smooth muscle of the rabbit corpus cavernosum (RCC) and to compare its effect with those of phentolamine, yohimbine and L-arginine. The effects of sildenafil, phentolamine, yohimbine and L-arginine were studied on the response of the RCC to electrical field stimulation (EFS) as well as on the phenylephrine (PE, 3 x 10(-6) M)-induced tone. EFS caused transient, frequency-dependent relaxation of the RCC that was inhibited by the nitric oxide synthase inhibitor NG-nitro-L-arginine (3 x 10(-5) M). Sildenafil (1 x 10(-9)-1 x 10(-6) M) and phentolamine (1 x 10(-9)-1 x 10(-6) M) enhanced the EFS-induced relaxation in a concentration-dependent manner with ED50 of 0.056 +/- 0.004 and 0.572 +/-0.035 microM at 8 Hz, respectively, yohimbine (3 x 10(-7)-3 x 10(-5) M) and L-arginine (3 x 10(-6)-3 x 10(-4) M) did not show significant effects (ED50 at 8 Hz = 35.84 +/-2.24 and 2.164 +/- 0.174 microM, respectively). Sildenafil (1 x 10(-9) and 1 x 10(-8) M) potentiated the EFS-induced relaxation caused by L-arginine (3 x 10(-5) m). Sildenafil, phentolamine, yohimbine and L-arginine reduced the PE-induced tone to different extents; the ED50 values were 0.81 +/- 0.097, 0.49 +/- 0.025 and 13.97 +/- 1.10 microM, respectively. Maximum concentration of L-arginine used failed to produce 50% relaxation (ED20 = 221.82 +/- 15.71 microM). The muscle relaxant effects of different combinations of sildenafil and L-arginine on PE-induced tone did not differ significantly from the sum of the individual effects. The results demonstrate that sildenafil, when compared to other drugs used in penile erection dysfunction, shows the highest potency on the nitrergic transmission in the RCC. On the other hand, phentolamine was found to possess the highest potency in inducing relaxation of RCC proving that its action is independent on the stimulated neurogenic system. In addition, the combination of less effective doses of sildenafil and L-arginine has a potential advantage on erectile functions. The importance of this combination remains to be solved clinically.

Erectile dysfunction: etiology and treatment in young and old patients

This study shows that endocrine and vascular etiologies of erectile dysfunction are more common in the older age group, whereas depression and marital discord are more common in the younger age group. There is considerable overlap between various factors pointing to the multifactorial nature of erectile dysfunction. Review of the treatment option chosen reveals that the invasive modalities were least common as compared with the popular vacuum tumescence device (although cumbersome) and testosterone replacement. Persons with low testosterone have an improved efficacy of sildenafil when hypogonadism is treated. Sildenafil with its ease of administration and high efficacy seems to be the logical first choice for most of the patients. If contraindications exist or treatment failures occur, other treatment options should be offered to patients.

Inhibition of the tonic contraction in the treatment of erectile dysfunction

Erectile dysfunction (ED) reduces the quality of life. It is estimated that 52% of men have some degree of ED, which is associated with ageing. While it is clear that there are a variety of current treatment options for ED, each of these has drawbacks and contraindications. A better understanding of the physiological mechanisms involved in penile erection will provide new ways to treat ED. This review not only focuses on the vasoconstrictors and vasodilators that control the state of contraction and relaxation of the corpora cavernosa smooth muscle, but also presents a novel Ca(2+)-sensitising pathway that contributes to maintaining the penis in the non-erect state. Studies have shown that inhibition of the RhoA/Rho-kinase signalling pathway induces penile erection. Further understanding of this RhoA/Rho-kinase pathway may provide a novel alternative treatment for ED.

Pharmacological management of erectile dysfunction

Erectile dysfunction (ED) is a common medical condition that affects the sexual life of millions of men worldwide. Many drugs are now available for treating ED; oral pharmacotherapy represents the first-line option for most patients with ED. Sildenafil, an inhibitor of the enzyme phosphodiesterase type 5, is currently the most widely prescribed oral agent and has a very satisfactory efficacy-safety profile in all patient categories. Apomorphine SL is a dopamine D1- and D2-receptor agonist which has recently been approved for marketing in Europe. It is best selected for treating patients with mild to moderate ED. Vardenafil and tadalafil are new phosphodiesterase type 5 inhibitors which are expected to be approved this year. Both of them have significant positive efficacy-safety profiles. Patients who do not respond to oral pharmacotherapy or who cannot use it are good candidates for intracavernosal and intraurethral therapy. Alprostadil is the most widely used drug, both for injection therapy and for the intraurethral route. The efficacy of second-line treatment is high but the attrition rate remains significant.

Yohimbine treatment of organic erectile dysfunction in a dose-escalation trial

Yohimbine has had questionable effects in men with organic erectile dysfunction. We conducted this study to better define the population of men responsive to yohimbine, because tobacco was thought to affect a regimen of yohimbine more than other risk factors. We measured nocturnal penile tumescence with the RigiScan monitor, hormone profiles, answers to the Florida Sexual Health Questionnaire, and clinical responses at baseline and after two different doses of yohimbine in 18 nonsmoking men with erectile dysfunction. Of the 18 men, nine (50%) were successful in completing intercourse in more than 75% of attempts. The yohimbine responders were men with less severe erectile dysfunction as manifested by improved increased rigidity on RigiScan testing, higher Florida Sexual Health Questionnaire scores, and slightly higher levels of serum testosterone. Yohimbine is an effective therapy to treat organic erectile dysfunction in some men with erectile dysfunction.

Short-term histopathologic effects of different intracavernosal agents on corpus cavernosum and antifibrotic activity of intracavernosal verapamil: an experimental study

OBJECTIVES

To evaluate the short-term effects of different intracavernosal agents and to investigate the antifibrotic effect of verapamil combined with these intracavernosal agents.

METHODS

Forty-five Sprague-Dawley rats weighing 400 to 500 g each (mean weight 435.27 +/- 13.65 g) were equally divided into nine groups (n = 5). Papaverine (group 1), alprostadil (group 2), sodium nitroprusside (group 3), and verapamil (group 4) were injected alone intracavernously in 0.2-mL doses. Verapamil combined with papaverine, alprostadil, and sodium nitroprusside in 0.2-mL doses (0.1 mL verapamil and 0.1 mL vasoactive agent) were injected in groups 5 through 7. Group 8 was kept as a control group without injection, and isotonic saline alone was injected in group 9 during the same period. The intracavernous injection was done twice weekly with a 4-day interval. At the end of the study, total penectomy and multiple liver biopsies were performed to evaluate the histopathologic effects of the vasoactive agents and to test the liver function.

RESULTS

In all groups, the structure of the corpora cavernosa was well preserved generally and appeared similar to the control tissue. However, localized edema, fibrosis, macrophage infiltration, and polymorphonuclear leukocytes were found only at the injection site. Although these findings were not different from the findings in the saline and alprostadil groups, they were slightly more extensive in the papaverine and sodium nitroprusside alone groups and also in the vasoactive agent plus verapamil groups. Although mononuclear lymphocyte infiltration was found in the portal areas, advancing into the liver parenchyma, the liver function tests were within normal limits.

CONCLUSIONS

We observed that intracavernous injection, except with nitroprusside, caused focal intracavernosal fibrosis and edema. We believe these effects might not be caused by just the drug, but also by needle trauma, since general fibrosis was not observed in the short term. However, nitroprusside has a severe fibrotic effect on cavernosal tissue in the short term. Moreover, intracavernous verapamil injection could not prevent the fibrosis in the short term.

Male sexual function and its disorders: physiology, pathophysiology, clinical investigation, and treatment

This review is designed to help the reproductive endocrinologist integrate his or her professional activity with those of other disciplines including urology, radiology, neurology, and psychology in order to successfully manage all of the inseparable aspects of male sexual and reproductive functioning. Significant advances in the field of male sexual physiology and pathophysiology and new methods of investigation and treatment of male sexual disorders are outlined. The review synthesizes available data on the following: norms of sexual organs, aging and sexuality, role of central and peripheral neurochemicals in each stage of the sexual cycle, role of corporeal smooth muscles in the hemodynamic control of erection and detumescence, influence of psychological factors, drugs, and disease on all aspects of sexual functioning, and use of nocturnal penile tumescence monitoring, imaging investigations, and neurophysiologic studies in the diagnostic workup of males with sexual dysfunction. Clinical algorithms are presented where appropriate. Extensive discussions on newly developed strategies in psychological and behavioral counseling, drug therapy, tissue engineering, nonsurgical devices, and surgical treatments for all forms of sexual disorders are also provided. Lastly, the effect of sexual dysfunction and its treatment on quality of life in affected men is addressed, along with recommendations for future research endeavors.

Lepidium meyenii Walp. improves sexual behaviour in male rats independently from its action on spontaneous locomotor activity

Lepidium meyenii Walpers (Maca) is traditionally employed in the Andean region for its supposed properties to improve energy and fertility. The aim of this study was to evaluate the effect of acute and chronic Maca pulverised root oral administration on rat sexual behaviour. Sixty male sexually experienced rats (20 group) were daily treated for 15 days with Maca 15 mg kg(-1), Maca 75 mg kg(-1) or saline 0.5 ml kg(-1). The following sexual performance parameters were evaluated at first and last day of treatment: 1st mount (ML), 1st intromission (IL), ejaculation (EL) and postejaculatory (PEL) latencies, intercopulatory interval (ICI) and copulatory efficacy (CE). An activity cage test was carried out to evaluate if Maca-induced locomotion changes could indirectly improve rat sexual performances. It was observed that both lower and higher Maca doses acutely decreased ML, IL and ICI in a significant way (P < 0.05), while only the 75 mg kg(-1) dose decreased the PEL (T = 29, P < 0.05). This effect seems to be the only one dose-dependent. After 15 days of treatment, both doses are able to significantly decrease ML, IL, EL and PEL, while the 75 mg kg(-1) dose decreased the ICI (T = 40, P < 0.05) too. IL, EL and PEL variations seem to be dose-related after chronic treatment. Moreover, chronic Maca treatment induced an apparently not dose-related increase in rat locomotion, during the second 10-min period of observation in the activity cage. The late in Maca-induced locomotion modification excludes that improvement of tested sexual performance parameters is related to an increase in rat aspecific activity. Thus, it was concluded that both acute and chronic Maca oral administration significantly improve sexual performance parameters in male rats.

Effect of sildenafil on non-adrenergic non-cholinergic neurotransmission in bovine penile small arteries

The purpose of the present study was to investigate the effect of the phosphodiesterase isoenzyme V inhibitor, sildenafil, on non-adrenergic non-cholinergic neurogenic relaxations of intracavernous isolated penile small arteries. Dense plexes of nerve fibres immunoreactive for neural nitric oxide (NO) synthase were observed in the adventitia-media junction of the penile small arteries. In 5-hydroxytryptamine-contracted preparations, the inhibitor of NO synthase, N(G)-nitro-L-arginine (L-NOARG), and of soluble guanylyl cyclase, 1H-[1,2,4]oxadiazolo[4,3,-a]quinoxalin-1-one (ODQ), reduced the electrical field stimulation-induced relaxations. Sildenafil and exogenous NO induced relaxations of penile small arteries. Sildenafil enhanced NO and vasoactive intestinal peptide-induced relaxations. Moreover, sildenafil increased the duration of the relaxations elicited by electrical field stimulation in penile small arteries and corpus cavernosum tissue. In the presence of L-NOARG, sildenafil only at supratherapeutic concentrations reduced the prazosin-sensitive contractions elicited by EFS in penile small arteries. Neurogenic NO-mediated and guanylyl cyclase-dependent relaxations of penile small arteries and corpus cavernosum tissue, considered to be associated with the vasodilatation leading to erection, are selectively enhanced by an inhibitor of phosphodiesterase V.

Pharmacotherapy for erectile dysfunction

Erectile dysfunction (ED) is defined as the consistent inability to obtain or maintain an erection for satisfactory sexual relations. An estimated 20-30 million men suffer from some degree of sexual dysfunction. The past 20 years of research on erectile physiology have increased our understanding of the biochemical factors and intracellular mechanisms responsible for corpus cavernosal smooth muscle contraction and relaxation, and revealed that ED is predominantly a disease of vascular origin. Since the advent of sildenafil (Viagra), there has been a resurgence of interest in ED, and an increase in patients presenting with this disease. A thorough knowledge of the physiology of erection is essential for future pharmacological innovations in the field of male ED.

Erectogenic effect of the selective phosphodiesterase type 5 inhibitor, DA-8159

DA-8159, a new phosphodiesterase 5 inhibitor, was assessed for its erectogenic potential by a penile erection test in rats, the relaxation of isolated rabbit corpus cavernosum (CC), and estimation of the intracavernous pressure (ICP) in the anesthetized dog. Oral administration of DA-8159 (0.3 to 1 mg/kg) increased the number of erections in rats with increasing dosage, with the highest penile erection index at 10 mg/kg. DA-8159 induced the relaxation of phenylephrine (PHE)-induced contractions in the rabbit CC and decreased the IC50 of the nitric oxide donor sodium nitroprusside (SNP) in a dose-dependent fashion. In pentobarbital-anesthetized dogs, the intravenous administration of DA-8159 (1 approximately 300 g/kg) potentiated the increase in ICP induced by the intracavernosal SNP in a dose-related manner. These findings suggest that DA-8159 has significant therapeutic potential in the treatment of erectile dysfunction.

Effects of SSRIs on sexual function: a critical review

Sexual problems are highly prevalent in both men and women and are affected by, among other factors, mood state, interpersonal functioning, and psychotropic medications. The incidence of antidepressant-induced sexual dysfunction is difficult to estimate because of the potentially confounding effects of the illness itself, social and interpersonal comorbidities, medication effects, and design and assessment problems in most studies. Estimates of sexual dysfunction vary from a small percentage to more than 80%. This article reviews current evidence regarding sexual side effects of selective serotonin reuptake inhibitors (SSRIs). Among the sexual side effects most commonly associated with SSRIs are delayed ejaculation and absent or delayed orgasm. Sexual desire (libido) and arousal difficulties are also frequently reported, although the specific association of these disorders to SSRI use has not been consistently shown. The effects of SSRIs on sexual functioning seem strongly dose-related and may vary among the group according to serotonin and dopamine reuptake mechanisms, induction of prolactin release, anticholinergic effects, inhibition of nitric oxide synthetase, and propensity for accumulation over time. A variety of strategies have been reported in the management of SSRI-induced sexual dysfunction, including waiting for tolerance to develop, dosage reduction, drug holidays, substitution of another antidepressant drug, and various augmentation strategies with 5-hydroxytryptamine-2 (5-HT2), 5-HT3, and alpha2 adrenergic receptor antagonists, 5-HT1A and dopamine receptor agonists, and phosphodiesterase (PDE5) enzyme inhibitors. Sexual side effects of SSRIs should not be viewed as entirely negative; some studies have shown improved control of premature ejaculation in men. The impacts of sexual side effects of SSRIs on treatment compliance and on patients' quality of life are important clinical considerations.

Yohimbine for erectile dysfunction: a systematic review and meta-analysis of randomized clinical trials

PURPOSE

Erectile dysfunction is a common problem, particularly in diabetics. It is associated with a considerable burden of suffering. No generally accepted drug treatment exists. We systematically reviewed and meta-analyzed all randomized, placebo controlled trials of yohimbine monotherapy for erectile dysfunction to determine its therapeutic efficacy. Our secondary aim was to evaluate the safety of yohimbine.

MATERIALS AND METHODS

We used computerized literature searches and standardized data extraction to rate methodological quality in a meta-analysis using computer statistical software.

RESULTS

Seven trials fit the predefined inclusion criteria. Overall methodological quality of these studies was satisfactory. The meta-analysis demonstrated that yohimbine is superior to placebo in the treatment of erectile dysfunction (odds ratio 3.85, 95% confidence interval 6.67 to 2.22). Serious adverse reactions were infrequent and reversible.

CONCLUSIONS

The benefit of yohimbine medication for erectile dysfunction seems to outweigh its risks. Therefore, yohimbine is believed to be a reasonable therapeutic option for erectile dysfunction that should be considered as initial pharmacological intervention.

Opportunities for the treatment of erectile dysfunction by modulation of the NO axis--alternatives to sildenafil citrate

Erectile function in man depends upon a complex interaction of psychogenic, neurologic, hormonal and vascular factors, and therefore the management of erectile dysfunction (ED) reflects this complexity of control. Therapeutic options include psychological and non-pharmacological approaches as well as drug treatments. The effectiveness of the type-5 cGMP phosphodiesterase inhibitor sildenafil citrate (Viagra) confirms the pivotal role of the NO-cGMP axis in promoting and maintaining erection. Although widely acclaimed, sildenafil leaves many questions unanswered, especially regarding its susceptibility to pharmacokinetic drug interactions, and its safety in patients with ischaemic heart disease and those taking nitrates. In view of the epidemiological link between erectile dysfunction and cardiovascular disease in the elderly, this limitation might have much broader implications. The presently available scientific documentation, although less extensive, indicates that NO donors, such as topically applied nitroglycerin (GTN; for example, 1-2 puffs of an ordinary GTN spray applied to the shaft of the penis), might be a reasonable alternative. Further larger-scale research on the efficacy and tolerability of topical GTN is needed to establish its full therapeutic potential in the treatment of erectile dysfunction.

A critical review of selective serotonin reuptake inhibitor-related sexual dysfunction; incidence, possible aetiology and implications for management

There is a high incidence of sexual dysfunction in the general population and sexual dysfunction is often an integral symptom of a depressive disorder. In addition, all antidepressants have effects on sexual functioning, as the result of side-effects of these medications and as a reflection of therapeutic success. The selective serotonin reuptake inhibitors (SSRIs) are clearly associated with delayed ejaculation, inability to ejaculate and absent or delayed orgasm. Furthermore, the incidence of sexual dysfunction obtained by patient self-report does not appear to reflect the true incidence of sexual dysfunction associated with antidepressant therapy and systematic inquiry is needed as sexual dysfunction may be an unrecognized cause of noncompliance. The SSRIs may have advantageous effects on sexual functioning and these may also be underreported due to the same factors resulting in an under-reporting of sexual side-effects in general. In addition, studies have suggested a role for the SSRIs in the management of premature ejaculation. The effects of SSRIs on sexual functioning are clearly dose-related and may vary amongst the group due to their relative effects on the serotonin and dopamine systems and the extent to which plasma levels of these drugs accumulate in the body over time. A variety of strategies have been found useful in the management of SSRI-induced sexual dysfunction including waiting for tolerance to develop, dosage reduction, drug holidays, switching to a different antidepressant and various augmentation strategies with 5-HT2, alpha2 adrenergic receptor antagonists and dopamine receptor agonists.