Is yohimbine effective in the treatment of organic impotence? Results of a controlled trial

Dietary Supplements for Erectile Dysfunction: Analysis of Marketed Products, Systematic Review, Meta-Analysis and Rational Use

The use of nutraceutical products to enhance male sexual performance has a long history, especially with regard to the treatment of erectile dysfunction (ED). Alternative treatments for ED are becoming increasingly popular, with growing interest from consumers, as well as increased revenue for manufacturers. Dietary supplements (DSs), which are a mixture of active ingredients, are mainly sold online. In randomized controlled trials, the molecules contained in DSs have demonstrated varying degrees of effectiveness, or even have no evidence to support their use. However, none of the studies carried out provided sufficient evidence to consider these products a first-line therapy. Therefore, the combination of the various active ingredients, especially in relation to the daily dose, leaves doubts about the real effectiveness. In order to evaluate the potential efficacy of DS formulations, we analyzed the products marketed in Italy using a scoring approach. A systematic review of the literature was performed to evaluate the effect of DS and to detect the active ingredients able to improve erectile function-called effective ingredients (EIs)-and their minimal effective daily dose (mED). A metanalysis identified some nutraceuticals, such as Panax ginseng, Tribulus terrestris and L-arginine, that are able to improve male sexual function. Based on the scoring system, 2 (8%) supplements matched with the cluster of higher expected efficacy, 3 (12%) with the lower efficacy cluster and 20 (80%) matched with the criterion of no expected efficacy. DSs marketed in Italy are usually blends of many substances that are frequently employed at a negligible dose or without any evidence.

Mondia whitei, an African Spice Inhibits Mitochondrial Permeability Transition in Rat Liver

Mondia whitei is an African traditional spice with aphrodisiac properties. Inhibition of mitochondrial permeability transition (mPT) pore is an important cytoprotective process essential for cell survival. In this study, the effects of methanol extract (ME), dichloromethane (DCMF), ethyl acetate (EF), and methanol fractions (MF) of Mondia whitei on mPT, mitochondrial ATPase, lipid peroxidation, testosterone hormone (TH), luteinizing hormone (LH), and follicle stimulating hormone (FSH) were investigated; sperm analyses were also carried out. Male experimental rats were treated intraperitoneally with 25, 50, and 100 mg/kg bw of ME, DCMF, EF, and MF of Mondia whitei for two weeks. The positive and the negative controls received sildenafil citrate and the vehicle, respectively. The results showed that mPT was inhibited by MF at the highest dose. The ME, DCMF, and MF did not enhance ATPase activity. The levels of TH, FSH, and LH varied linearly with the drug dose only in EF. Malondialdehyde levels in the treated groups were significantly higher than the normal control. There were no significant defects in sperm produced by the animals in all the treated groups relative to the control. This study showed that the extract and fractions of Mondia whitei have cytoprotective effects and may prevent mitochondrial-mediated cell death.

Virtualizing the p-ANAPL library: a step towards drug discovery from African medicinal plants

BACKGROUND

Natural products play a key role in drug discovery programs, both serving as drugs and as templates for the synthesis of drugs, even though the quantities and availabilities of samples for screening are often limitted.

EXPERIMENTAL APPROACH

A current collection of physical samples of > 500 compound derived from African medicinal plants aimed at screening for drug discovery has been made by donations from several researchers from across the continent to be directly available for drug discovery programs. A virtual library of 3D structures of compounds has been generated and Lipinski's "Rule of Five" has been used to evaluate likely oral availability of the samples.

RESULTS

A majority of the compound samples are made of flavonoids and about two thirds (2/3) are compliant to the "Rule of Five". The pharmacological profiles of thirty six (36) selected compounds in the collection have been discussed.

CONCLUSIONS AND IMPLICATIONS

The p-ANAPL library is the largest physical collection of natural products derived from African medicinal plants directly available for screening purposes. The virtual library is also available and could be employed in virtual screening campaigns.

The uniqueness and therapeutic value of natural products from West African medicinal plants. Part I: uniqueness and chemotaxonomy

This review gives an in depth coverage of the natural products derived from West African medicinal plants with diverse biological activities.

Natural aphrodisiacs

INTRODUCTION

The search for a remedy or a prescription that can enhance sexual function and/or treat male erectile dysfunction has been an obsession throughout known history. Whether it was an Eastern civilization or a Western one, religious or atheist, man's aspiration for a better or best "manhood" has been a history-time goal.

AIM

This review will discuss the current research done on the most popular natural aphrodisiacs and examine the weight of evidence to support or discourage the use of any of these substances to enhance sexual desire and/or function.

METHODS

Review of the current evidence on the use of natural substances as aphrodisiacs.

MAIN OUTCOME MEASURES

Efficacy of natural aphrodisiacs in enhancing sexual function in men and women.

RESULTS

There is little evidence from literature to recommend the usage of natural aphrodisiacs for the enhancement of sexual desire and/or performance. Data on yohimbine's efficacy does not support the wide use of the drug, which has only mild effects in the treatment of psychogenic ED. Although there's a positive trend towards recommending ginseng as an effective aphrodisiac, however, more in depth studies involving large number of subjects and its mechanism of action are needed before definite conclusions could be reached. Data on the use of natural aphrodisiacs in women is limited.

CONCLUSIONS

The current body of objective evidence does not support the use of any natural aphrodisiac as an effective treatment for male or female sexual dysfunctions. Potent men and men with ED will continue the search for natural aphrodisiacs despite the current disappointing data on their effectiveness. Care should be taken regarding the fraud addition of sildenafil analogues to natural aphrodisiacs.

Percutaneous perineal electrostimulation induces erection: clinical significance in patients with spinal cord injury and erectile dysfunction

OBJECTIVES

Approximately one third to one half of the penis is embedded in the pelvis and can be felt through the scrotum and in the perineum. The main arteries and nerves enter the penis through this perineal part of the penis, which seems to represent a highly sensitive area. We investigated the hypothesis that percutaneous perineal stimulation evokes erection in patients with neurogenic erectile dysfunction.

METHODS

Percutaneous electrostimulation of the perineum (PESP) with synchronous intracorporeal pressure (ICP) recording was performed in 28 healthy volunteers (age 36.3 +/-7.4 y) and 18 patients (age 36.6 +/- 6.8 y) with complete neurogenic erectile dysfunction (NED). Current was delivered in a sine wave summation fashion. Average maximal voltages and number of stimulations delivered per session were 15 to 18 volts and 15 to 25 stimulations, respectively.

RESULTS

PESP of healthy volunteers effected an ICP increase (P < 0.0001), which returned to the basal value upon stimulation cessation. The latent period recorded was 2.5 +/- 0.2 seconds. Results were reproducible on repeated PESP in the same subject but with an increase of the latent period. Patients with NED recorded an ICP increase that was lower (P < 0.05) and a latent period that was longer (P < 0.0001) than those of healthy volunteers.

CONCLUSION

PESP effected ICP increase in the healthy volunteers and patients with NED. The ICP was significantly higher and latent period shorter in the healthy volunteers than in the NED patients. PESP may be of value in the treatment of patients with NED, provided that further studies are performed to reproduce these results.

Herbal drugs of abuse: an emerging problem

Some herbal products are emerging as popular drugs for recreational abuse. Plant and herbal supplements used recreationally can have a wide spectrum of clinical effects ranging from euphoric and stimulant effects to hallucinogenic experiences. Despite the potential for abuse, addiction, and serious adverse effects, there may be a false perception that these products are all safe, legal, and organic. These perceptions and the ease of accessibility to herbal products could result in greater potential for recreational abuse and subsequent complications presenting to emergency departments. Health care professionals must be cognizant of this emerging problem as increased media coverage and marketing have made these products accessible and recognizable to many young adults and teenagers.

The role of phosphodiesterase inhibitors in impotence

Penile erection is mediated by nitric oxide (NO) and its second messenger cyclic guanosine monophosphate (cGMP). The activity of cGMP is modulated by the enzyme phosphodiesterase (PDE). The most important physiological isoform of the enzyme in the penis is PDE5. Sildenafil is a specific inhibitor of this enzyme which potentiates nitrergic cavernosal relaxation in vitro and in animals. Clinical studies suggest that it is effective in the treatment of male erectile dysfunction (MED), which would make it the first orally active therapy for this condition.

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.

Neurochemical aspects of the sexual response cycle

What drives the human sexual response cycle? The human sexual response cycle is a highly complex phenomenon that encompasses many transmitters and transmitter systems centrally and peripherally. The endocrine system is also intricately involved in the brain and in the periphery organs. Integration of these systems is a function of the nervous system that ultimately produces a vast array of cognitive, emotional, physiological, and behavioral responses. Therefore, it is not surprising that a disturbance in even a single system will lead to dysfunction in one or more phases of the sexual response cycle. This article highlights the complex roles the aminergic system plays along with key hormones that are equally involved. The article also points out how rudimentary and fragmented our knowledge is in this field and how few controlled studies are available. The potential for development of specific agents that target selective sexual dysfunctions is exemplified in sildenafil, the first such agent ever to be brought to market.

Long-term use of sildenafil

The treatment of erectile dysfunction (ED) has been revolutionised by new agents to inhibit the enzyme PDE5. The scientific basis of this treatment of ED includes relaxation of the corpus cavernosum smooth muscle tissue by inhibition of PDE5 that breaks down cGMP, the key pathway for the production of erectile function in humans. Many clinical studies, both pre- and post-marketing, have demonstrated the clinical efficacy and safety of sildenafil (Viagra, Pfizer) - the first approved selective PDE inhibitor for the treatment of ED. Sildenafil is inhibitory of PDE5 at a rate tenfold higher than for the next PDE (PDE6), which produces visual changes through the retinal rods. Its clinical effectiveness has been well documented in the majority of men with ED irrespective of aetiology. The aetiology of ED, also, does not appear to effect the function of sildenafil in relaxing corpus cavernosum smooth muscle tissue. Adverse events are usually associated with the vascular changes from PDE5 inhibition. These include headache and flushing. Each of these adverse events, however, declines with medication use. With the use of sildenafil, it has been clearly, clinically demonstrated that the selective inhibition of PDE5 is an appropriate, effective, safe method for the treatment of ED of all aetiologies and severities.

Recent advances in the treatment of erectile dysfunction in patients with diabetes mellitus

OBJECTIVE

To present current information on the pathogenesis of and available therapeutic options for erectile dysfunction (ED) in patients with diabetes.

METHODS

We provide a detailed review of the following topics: (1) peripheral and central neurotransmitter pathways involved in the penile erectile process (for example, nitric oxide, acetylcholine, vasoactive intestinal polypeptide, and prostaglandin E(1)), (2) pathogenesis of ED in patients with diabetes (vascular insufficiency, endothelial dysfunction, and autonomic neuropathy), (3) currently available treatment options for ED and their advantages and disadvantages, (4) potential new avenues for future research, and (5) the possibility of preventive treatment.

RESULTS

Clearly a need exists for effective treatment options for ED in patients with diabetes. Because the development of ED in patients with diabetes is often caused by several interrelated mechanisms, including vascular disease, endothelial dysfunction, autonomic neuropathy, hormone imbalance, and certain medications, a thorough understanding of the various pathways involved in penile erection and their modulation in diabetes is essential for physicians to design an effective treatment plan. Interventions that modulate the erectile pathway at different points include therapies that enhance the erectile mechanism (amplification of the nitric oxide pathway), inhibit the detumescence mechanism, or affect the final common pathway by augmenting smooth muscle relaxation. Oral therapy, intracavernosal injections, transurethral pellets, combination therapy, and surgical procedures are available treatment strategies.

CONCLUSION

Despite the availability of many treatment options for ED, early intervention and prevention (by such measures as improved glycemic control and general reduction of associated risk factors) should be emphasized because many of the diabetes-related complications leading to ED are irreversible.

Efficacy and safety of a novel combination of L-arginine glutamate and yohimbine hydrochloride: a new oral therapy for erectile dysfunction

PURPOSE

The goal of this double-blind, placebo-controlled, three-way crossover, randomized clinical trial was to compare the efficacy and safety of the combination of 6g of L-arginine glutamate and 6 mg of yohimbine hydrochloride (AY) with that of 6 mg of yohimbine hydrochloride (YP) alone and that of placebo (PP) alone, for the treatment of erectile dysfunction (ED).

MATERIALS AND METHODS

Forty-five patients were included in this study. During each of the 2-week, crossover periods, drug was administered orally, one to two hours before intended sexual intercourse. The primary endpoint was change in the Erectile Function Domain score of the International Index of Erectile Function (IIEF). The secondary endpoints were patient and investigator assessments of treatment success.

RESULTS

At the end of each treatment period, the Erectile Function Domain scores for AY, YP and PP were 17.2+/-7.17, 15.4+/-6.49 and 14.1+/-6.56, respectively. The difference between AY and PP was statistically significant (p=0.006). When stratified according to baseline scores over 14, those patients with mild to moderate MED had a better Erectile Function Domain response to treatment (AY=22.2+/-4.99, YP=18.2+/-5.59, PP=16.9+/-6.91, respectively) than those with scores 14 and below (AY=12.4+/-5.48, YP=12.7+/-6.25, PP=11.4+/-5.02, respectively). Investigators' and patients' assessment of efficacy was significantly improved by YP over PP.

CONCLUSIONS

This pilot study shows that the on-demand oral administration of the L-arginine glutamate 6g and 6 mg yohimbine combination is effective in improving erectile function in patients with mild to moderate ED. It appears to be a promising addition to first-line therapy for ED.

Pharmacological aspects of erectile dysfunction

Erectile dysfunction (ED) is a common problem with a prevalence of approximately 50% in men aged 40 to 70. There are several etiologies for ED including vasculogenic, neurogenic, hormonal and/or psychogenic factors; one-fourth of ED cases can be drug-related. Penile erection involves a complex interaction between the CNS and local factors. It is a neurovascular event modulated by psychological and hormonal factors. Pharmacologically, neural modulation and endocrine status are very important to attaining penile erection. There have been several significant advances for the pharmacologic treatment of ED. Treatments include agents that are not only orally effective, but possess either local or central acting mechanisms of action. Apomorphine, a centrally-acting agent, is effective in the treatment of ED. Sildenafil, another orally effective agent, acts by inhibiting cyclic GMP-specific phosphodiesterase Type V. Testosterone can be effective transdermally. Non-orally active agents include alprostadil and papaverine. Phentolamine and trazodone are effective in selected cases. Some agents can interact with other medications. Several pharmacological agents, some with central-acting mechanisms and some with Iocally-acting vascular effects, are therapeutically useful in the treatment of ED.

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.

Yohimbine: a clinical review

Although yohimbine (YOH) has been available for the treatment of male erectile dysfunction (ED) for longer than Viagra, there is a perception that little is known about the clinical performance of the drug. This review attempts, by comprehensive analysis of the literature, to cover the clinical, pharmacological, and therapeutic profiles of YOH, relevant to its potential utility in the management of patients with ED. Relatively few well-designed studies have been completed. From these, however, it can be concluded that YOH as monotherapy possesses only modest efficacy in ED patients. In acute and chronic (long-term) studies, YOH has been found to be relatively free of side effects over the dose range predicted to be effective in ED. At much higher doses, the most frequently observed effects, consistent with the primary pharmacological action of the drug, are elevation of blood pressure, a slight anxiogenic action, and increased frequency of urination. These side effects are all easily reversible on termination of YOH therapy. There is increasing evidence that the erectogenic action of YOH can be augmented by concomitant administration of agents that augment the release and/or action of nitric oxide in the corpus cavernosum. YOH has yet to be studied in female sexual dysfunction. Overall, the benefit risk profile of YOH would indicate that it has potential, more probably as part of a combination strategy, e.g., with a drug that enhances the nitric oxide pathway, in the treatment of ED.

Pharmacology of erectile function and dysfunction

Central regulation of the erectile process involves several transmitters, including dopamine, serotonin, noradrenaline, and nitric oxide, and peptides, such as oxytocin and ACTH/alpha-MSH. These systems may be targets for future drugs designed to treat erectile dysfunction. Peripherally, the different steps involved in neurotransmission, impulse propagation, and intracellular transduction of neural signals in penile smooth muscles need further investigation. Continued studies of the interactions between different transmitters/modulators may reveal new combination therapies. Increased knowledge of the changes in penile tissues associated with erectile dysfunction may explain the pathogenetic mechanisms and help to prevent the disorder.

Adverse effects of herbal treatment of cardiovascular disease: what the physician must know

The increasing use of herbal products by patients with cardiovascular disease represents a clinical challenge to physicians. The use of herbal products is increasing in our society, and less than 50% of patients using herbal products report this information to their physicians. In addition, physicians often lack the knowledge base for herbal medications to effectively counsel patients regarding adverse effects and potential herb-drug interactions. This article reviews Western and traditional Chinese herbs that are commonly used by patients with cardiovascular diseases, herbs noted to have adverse cardiovascular effects, and herbs that may potentially interact with commonly prescribed cardiovascular medications.

New treatment for erectile dysfunction

Numerous advances have been made in our understanding of the evaluation and treatment of erectile dysfunction. Numerous treatment options are currently available. Treatment of this disorder was revolutionized by the introduction of sildenafil, an oral vasoactive agent that has a peripheral mechanism of action, blocking the degradation of cyclic guanosine monophosphate, and thus augmenting the erectogenic effect of sexual stimulation. This agent has proven efficacy in a variety of patient populations, including psychiatric patients. Clinical series suggest that this agent will reverse erectile dysfunction induced by psychoactive agents. Thus, it may play a role in decreasing treatment noncompliance associated with drug-induced sexual dysfunction. Another novel agent that is in development may be of special interest to psychiatrists. Apomorphine is a central dopamine agonist that is believed to act at the level of the paraventricular nucleus of the hypothalamus. As new agents are evolving, our understanding of the neurobiology of sexual function is advancing.

Non-surgical management of erectile dysfunction

Erectile dysfunction is a common and distressing medical condition that is now highly amenable to treatment almost irrespective of the cause. Safe, non-surgical treatments with unequivocal efficacy are psychological therapy, intracorporeal injection of vasoactive drugs, transurethral vasodilators and oral sildenafil, all of which have been reported to have a 50-70% overall response rate. Vacuum constriction devices are acceptable for some, usually older patients and oral yohimbine is thought to have marginal efficacy. Local creams to induce or enhance erectile function are currently being investigated. There is no place for androgen supplementation unless the patient is profoundly hypogonadal. Treatment of hyperprolactinaemia is very effective but is a rare cause of erectile dysfunction. As intercourse may entail an unfamiliar level of physical activity, it is sensible to ensure that the patient is able to climb a flight or two of stairs comfortably without provoking undue breathlessness or chest pain and to provide suitable advice about technique before commencing treatment. Once it is clear to the patients that erectile dysfunction can be satisfactorily overcome, the long-term use of treatments to do so tends to wane. Thus, although the prospect of effective treatment for what had been for many a distressing life sentence has the potential to place new demands on the health service, there is no evidence that restrictions on prescribing will prove economically rational.

Biopharmaceutics and metabolism of yohimbine in humans

The biopharmaceutics of yohimbine (YO) and the pharmacokinetics of 10-hydroxy-yohimbine (10-OH-YO) and 11-hydroxy-yohimbine (11-OH-YO) were investigated in healthy subjects following i.v. (5 mg) and oral (8 mg) dosing. One subject was found as a slow hydroxylator of YO. The mean (+/-S.D.) oral absolute bioavailability of YO was 22.3+/-21. 5%. Total plasma clearance (CL) and renal clearance (CL(r)) of YO following i.v. dosing were 0.728+/-0.256 ml/min and 0.001+/-0.002 ml/min, respectively. Based on the steady-state volume of distribution (V(ss)), YO had a relatively low distribution (V(ss) = 32.2+/-12.1 l). The overall renal excretion of YO, 10-OH-YO and 11-OH-YO, expressed as percent of the dose of YO administered, were not different following i.v. and oral dosing, and were around 0.1, 0.2 and 14%, respectively. Following i.v. dosing of YO, the mean apparent terminal half-life of 11-OH-YO (347+/-63 min) was almost four times higher than that of YO (91.0+/-33.6 min) suggesting an elimination rate-limited kinetics for 11-OH-YO.

Current treatment of impotence: Viagra and other options

This article looks at the current treatment of impotence and recent developments in the pharmacological treatment of erectile dysfunction. Sildenafil (Viagra) threatens to become the most costly drug treatment within the NHS, but its value may be overestimated and its effectiveness under-researched. This oral treatment has received a lot of recent press attention and is perhaps overshadowing the value of established treatment regimens. Pharmacological treatment may also fail to tackle the important psychological problems often associated with this distressing condition.

Safety and efficacy of sildenafil citrate in the treatment of male erectile dysfunction

Sildenafil citrate, an oral therapy for erectile dysfunction, is a selective inhibitor of cyclic guanosine monophosphate (cGMP)-specific phosphodiesterase type 5 (PDE5), the predominant isozyme metabolizing cGMP in the corpus cavernosum. Chemically, it is a compound of the pyrazolo-pyrimidinyl-methylpiperazine class. Sildenafil has no direct relaxant effect on human corpus cavernosum but enhances the relaxant effect of nitric oxide (NO) on the corpus cavernosum by inhibiting PDE5, which is responsible for degradation of cGMP in this tissue. When sexual stimulation causes local release of NO, inhibition of PDE5 by sildenafil increases concentrations of cGMP in the corpus cavernosum, causing smooth muscle relaxation and blood flow into the penis, resulting in an erection. Sildenafil at recommended doses has no effect in the absence of sexual stimulation. The drug is rapidly absorbed after oral administration, with absolute bioavailability of 40%. Its pharmacokinetics are dose proportional over the recommended dosage range. Maximum plasma concentrations are reached within 30 to 120 minutes after oral dosing in the fasting state. Sildenafil is cleared predominantly by the hepatic microsomal isoenzymes CYP3A4 (major route) and CYP2C9 (minor route). Clinical studies assessed the effect of sildenafil on the ability of men with erectile dysfunction to engage in sexual activity and, specifically, to achieve and maintain an erection sufficient for satisfactory sexual intercourse. Sildenafil was evaluated at doses of 25, 50, and 100 mg in randomized, double-masked, placebo-controlled clinical trials of up to 6 months' duration. The drug was administered to hundreds of patients aged 19 to 87 years having erectile dysfunction of various etiologies for a mean duration of 5 years. Sildenafil was associated with statistically significant improvement in erectile function compared with placebo. Adverse effects reported at a rate of >2% were headache, flushing, dyspepsia, nasal congestion, urinary tract infection, abnormal vision, diarrhea, dizziness, and rash. No cases of priapism were reported. The use of sildenafil is contraindicated in men who are taking organic nitrates, because of the potential for a precipitous decrease in blood pressure. Postmarketing reports and surveillance have revealed at least 39 deaths with sildenafil use in men having a history of heart disease, men taking nitrate medications, and men in poor physical health due to lack of exercise. Many of the men who experienced serious adverse effects or death had a variety of concomitant diseases and were taking multiple medications.

When patients request the impotence pill

Erectile dysfunction is a common condition affecting men over age 50. With the recent increase in public awareness about available therapies, more and more men are seeking help. Primary care physicians usually can prescribe first-line treatments without acquiring additional equipment or staff. Patients who are not satisfied with oral medication, vacuum devices, injection therapy, or intraurethral suppositories may be referred to a urologist for further treatment. Development of new medical therapies is ongoing, and within the next few years, we expect to see the introduction of more medications for treatment of erectile dysfunction. Some agents act peripherally on the penile circulation and others centrally on the portion of the brain involved in producing erections.

Medical treatment of erectile dysfunction

There has been a tremendous increase in demand for the treatment of erectile dysfunction in the last 10 years. This has occurred partly because of a greater understanding and awareness by both the general public and clinicians, and also because there now exists a range of effective treatments. The choice of treatments is increasing rapidly and novel delivery systems which may be more patient-friendly than intracavernosal injections are now becoming available. We review the published data on effectiveness and safety of the currently available treatments and discuss recent advances in oral therapy, as these drugs are likely to become available in the near future.