The safety of phosphodiesterase type 5 inhibitors for erectile dysfunction

Synthetic approaches and clinical application of representative small-molecule inhibitors of phosphodiesterase

Phosphodiesterases (PDEs) constitute a family of enzymes that play a pivotal role in the regulation of intracellular levels of cyclic nucleotides, including cyclic adenosine monophosphate (cAMP) and cyclic guanosine monophosphate (cGMP). Dysregulation of PDE activity has been implicated in diverse pathological conditions encompassing cardiovascular disorders, pulmonary diseases, and neurological disorders. Small-molecule inhibitors targeting PDEs have emerged as promising therapeutic agents for the treatment of these ailments, some of which have been approved for their clinical use. Despite their success, challenges such as resistance mechanisms and off-target effects persist, urging continuous research for the development of next-generation PDE inhibitors. The objective of this review is to provide an overview of the synthesis and clinical application of representative approved small-molecule PDE inhibitors, with the aim of offering guidance for further advancements in the development of novel PDE inhibitors.

Spontaneous erectile function recovery among young men with erectile dysfunction taking tadalafil 5 mg once a day

BACKGROUND

Daily (once a day [OaD]) tadalafil intake is a valuable option for men favoring spontaneous over scheduled sexual intercourse.

AIM

The study sought to assess the rate of and the clinical factors associated with spontaneous, medication-free erectile function (EF) recovery after discontinuation of tadalafil 5 mg OaD in a cohort of young men seeking first medical help for psychogenic erectile dysfunction (ED) as their primary complaint.

METHODS

Data from 96 consecutive patients <50 years of age seeking first medical help for ED and prescribed tadalafil 5 mg OaD were analyzed. Patients completed the International Index of Erectile Function (IIEF) and underwent baseline penile color Doppler ultrasound. Follow-up involved clinical assessments or phone interviews. Spontaneous medication-free EF recovery was defined as IIEF EF domain score >22 after tadalafil discontinuation, prompting cessation of follow-up. Descriptive statistics compared tadalafil OaD responders and nonresponders. Cox regression hazard models explored the association between baseline characteristics and EF recovery risk post-drug discontinuation. Kaplan-Meier analyses estimated EF recovery probability over time.

OUTCOMES

The primary outcome was EF recovery after discontinuation of tadalafil 5 mg OaD.

RESULTS

Overall, median age was 39 (interquartile range [IQR], 32-45) years. Of all, 82 (85.4%) patients achieved EF recovery after tadalafil OaD discontinuation, while 14 (14.6%) patients were identified as nonresponders. Median tadalafil usage time (from beginning to discontinuation) was 3 (IQR, 2-11) months. The most common treatment-emergent adverse event was headache in 9 (9.4%) patients. Nonresponders were older (43 [IQR, 42-45] years vs 38 [IQR, 31-44] years; P = .03), had higher body mass index (25.5 [IQR, 23.4-29.9] kg/m2 vs 23.6 [IQR, 21.8-25.9] kg/m2; P = .04), and reported lower baseline IIEF EF domain scores (12 [IQR, 7-15] vs 15 [IQR, 10-22]; P = .02) than responders. Nonresponders and responders did not differ in terms of baseline ED severity, Charlson comorbidity index, smoking, alcohol consumption, regular physical exercise, and color Doppler ultrasound parameters. Upon Cox regression analysis, younger age (hazard ratio, 0.95; 95% confidence interval, 0.92-0.99; P = .01) was associated to EF recovery, after adjusting for baseline ED severity, body mass index, smoking, and Charlson comorbidity index ≥1. The Kaplan-Meier analysis displays the probability of EF recovery over time, indicating rates of 43%, 60%, and 72% at 3-, 6-, and 12-month follow-up intervals, respectively.

CLINICAL IMPLICATIONS

Tadalafil 5 mg OaD is an effective short-term treatment for psychogenic ED, allowing its discontinuation after achieving a normal medication-free EF.

STRENGTHS AND LIMITATIONS

The main limitations are the limited number of participants and the potential neglect of confounding factors.

CONCLUSION

Almost 1 out of 2 young men with primary psychogenic ED who were prescribed with tadalafil 5 mg OaD recovered spontaneous medication-free EF after 3 months of treatment. Overall, the younger the patient was, the higher the chance there was of spontaneous EF recovery after drug discontinuation.

Hormones and Aging: An Endocrine Society Scientific Statement

Multiple changes occur across various endocrine systems as an individual ages. The understanding of the factors that cause age-related changes and how they should be managed clinically is evolving. This statement reviews the current state of research in the growth hormone, adrenal, ovarian, testicular, and thyroid axes, as well as in osteoporosis, vitamin D deficiency, type 2 diabetes, and water metabolism, with a specific focus on older individuals. Each section describes the natural history and observational data in older individuals, available therapies, clinical trial data on efficacy and safety in older individuals, key points, and scientific gaps. The goal of this statement is to inform future research that refines prevention and treatment strategies in age-associated endocrine conditions, with the goal of improving the health of older individuals.

Knowledge, attitude, and practice (KAP) regarding erectile dysfunction disease and its medications among community pharmacy technicians in Mogadishu Somalia

Background

Erectile Dysfunction (ED) is the most common sexual dysfunction worldwide. This study is the first reported from Somalia to the best of our knowledge.

Objective

The current study aimed to assess knowledge, attitude, and practice (KAP) regarding erectile dysfunction disease and its medications among community pharmacy technicians in Mogadishu, Somalia.

Method

The current is a cross-sectional descriptive study conducted among pharmacy technicians in Mogadishu to assess their KAP regarding erectile dysfunction disease and its medications. A convenient sampling technique was used. A structured questionnaire contained 45 questions, including; demographic characteristics (4 items), the knowledge of erectile dysfunction disease and its medications (18 items), attitudes (5 items), and practice (15 items) were assessed among technicians. A total of 200 respondents participated in the study.

Results

Knowledge. 79 and 72.5% of technicians comprehended the condition of ED and whom it affects; however, about half did not know the underlying risk factors and complications associated with PDE5 inhibitors. Attitude: 77–85% of technicians believe medication requires prescriptions, medications may have complications, and quality medications are essential. Practice: 64% of technicians give ED medication with prescriptions, and 85% do not consult a physician. 64.5% of technicians always provide the same type of medication, and 63% do not give the same dose to each client. About half of the technicians also vend herbal medicines to clients, such as honey, fish, and sea urchins.

Conclusion

The findings of this study suggest pharmacy technicians have some knowledge, although not sufficient for understanding the risks and complications of medications. Technicians did not engage in good standard practices despite this knowledge and attitudes. These findings highlight the need for regulations to support good practice among pharmacy technicians and the quality, safety, and efficacy of medicines in Mogadishu by establishing the National Medicine Regulatory Authority.

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ED is the most common sexual dysfunction worldwide, approximately 150 million men are affected and impaired their quality of life including a negative psychosocial impact, feelings of shame, embarrassment, and depression.

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Community pharmacy technicians have often been regarded as an underused clinical care resource.

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There can be no one cure-all solution in encouraging men to present early with ED and accept complete lifestyle changes and treatment packages unless continuous medical education and capacity-building programs are promoted throughout primary care and at the national setting level.

Long-term high-dose L-arginine supplementation in patients with vasculogenic erectile dysfunction: a multicentre, double-blind, randomized, placebo-controlled clinical trial

PURPOSE

The current randomized, double-blind, placebo-controlled clinical trial addressed the effects on penile erectile function of relatively high daily oral doses (6 g/day) of L-ARG for 3 months (N = 51) compared to placebo (N = 47), in patients with vasculogenic ED, with comparison between mild-moderate and severe vasculogenic ED.

METHODS

The outcome measures included IIEF-6 score and cavernous arteries peak systolic flow velocity (PSV) at dynamic penile duplex ultrasonography (PDU).

RESULTS

L-ARG supplementation for 3 months significantly increased IIEF-6 score in the overall cohort (p < 0.0001) and in subgroups of patients with mild-moderate (p < 0.0001) and severe (p = 0.007) vasculogenic ED; PSV was significantly increased in the overall cohort (p < 0.0001) and in patients with mild-moderate (p < 0.0001), but not severe vasculogenic ED. At study completion, 74% of patients improved ED degree category, although only 24% of patients, mainly belonging to the baseline category of mild ED, reached IIEF-6 scores compatible with absence of ED; moreover, 20% of patients, exclusively belonging to the baseline category of mild-moderate vasculogenic ED, reached PSV values compatible with absence of ED.

CONCLUSION

The results of the current study demonstrated that supplementation with relatively high doses of L-ARG as a single compound for 3 months significantly improved penile erectile function, assessed by both IIEF-6 score and PSV at dynamic PDU in patients with mild-moderate, and improved IIEF-6 score, but not PSV, in patients with severe vasculogenic ED, therefore suggesting that L-ARG might be an alternative treatment in mild-moderate vasculogenic ED patients experiencing adverse effects or with contraindications for chronic treatment with PDE5i compounds.

Cyclic Dipeptides: The Biological and Structural Landscape with Special Focus on the Anti-Cancer Proline-Based Scaffold

Cyclic dipeptides, also know as diketopiperazines (DKP), the simplest cyclic forms of peptides widespread in nature, are unsurpassed in their structural and bio-functional diversity. DKPs, especially those containing proline, due to their unique features such as, inter alia, extra-rigid conformation, high resistance to enzyme degradation, increased cell permeability, and expandable ability to bind a diverse of targets with better affinity, have emerged in the last years as biologically pre-validated platforms for the drug discovery. Recent advances have revealed their enormous potential in the development of next-generation theranostics, smart delivery systems, and biomaterials. Here, we present an updated review on the biological and structural profile of these appealing biomolecules, with a particular emphasis on those with anticancer properties, since cancers are the main cause of death all over the world. Additionally, we provide a consideration on supramolecular structuring and synthons, based on the proline-based DKP privileged scaffold, for inspiration in the design of compound libraries in search of ideal ligands, innovative self-assembled nanomaterials, and bio-functional architectures.

Safety and efficacy of botulinum neurotoxin in the treatment of erectile dysfunction refractory to phosphodiesterase inhibitors: Results of a randomized controlled trial

BACKGROUND

There has been recent interest in the use of botulinum neurotoxin (BoNT) in the field of Andrology, whereby it has been investigated in the treatment of penile retraction and premature ejaculation.

OBJECTIVES

To evaluate the safety and efficacy of intracavernosal BoNT-A injection in the treatment of patients with erectile dysfunction (ED) refractory to oral phosphodiesterase inhibitors (PDE5Is).

PATIENTS AND METHODS

A double-blind randomized placebo-controlled prospective comparative study conducted at one center and involved 70 patients with ED refractory to PDE5Is. At baseline, the following data were collected: erection hardness score (EHS), peak systolic velocity (PSV), end diastolic velocity (EDV), sexual health inventory for men (SHIM), and the sexual encounter profile 2&3 (SEP-2&3) questionnaires. Treatment group (n = 35) received a single ICI of 100 units of BoNT-A in 2 ml of saline and control group (n = 35) received a single ICI of 2 ml of saline. EHS, PSV, and EDV were assessed at 2 weeks post treatment. SHIM, SEP-2, SEP-3, and global assessment questionnaire (GAQ-Q1&Q2) were completed at 2-, 6-, and 12-weeks post treatment.

RESULTS

Two weeks post treatment, the treatment group showed a statistically significant improvement in the mean EHS, PSV, EDV, and GAQ-Q1 positive responders (p < 0.001) compared to the control group. At 6- and 12-weeks post treatment, the treatment group showed a statistically significant improvement in the SHIM scores, SEP-2, and GAQ-Q1&Q2 positive responders compared to the control group. At 6 weeks, where there was a 5-point improvement in the mean SHIM score of the treatment group (10±5.9 from 5.4±1.7 at baseline) versus no improvement in the placebo group, 18 patients in the treatment group (53%) were able to have an erection hard enough for vaginal penetration versus only one patient in the control group.

CONCLUSION

BoNT-A is safe and effective as a potential treatment for ED refractory to PDE5I therapy.

Cavernous artery intima-media thickness predicts the response to sildenafil in erectile dysfunction patients as a morphological parameter

While the intima-media thickness (IMT) of the cavernous artery was used for diagnosis for vascular erectile dysfunction (ED) with more accuracy than the peak systolic velocity, the role of the IMT in predicting treatment responses remained unexamined. A total of 136 patients with ED were enrolled. The baseline clinical and laboratory characteristics were collected. Penile Doppler ultrasonography (PDU) was performed on all patients by a blinded sonographer. Sildenafil was administrated to all patients with an adjusted dose of 50 or 100 mg on demand over a period of 3 months. A follow-up was conducted on all patients using the Erectile Hardness Score (EHS) questionnaire along with the visual and tactile version of the standardised EHS tool. The peak systolic velocity (PSV) and IMT were compared between sildenafil responders and sildenafil nonresponders, while receiver operator characteristic (ROC) curves were used to calculate the cut-off values and compare the test power respectively. There was no statistical difference from the baseline characteristics. The IMT of cavernous artery was more accurate than PSV to predict the sildenafil response (AUC = 0.809, 0.626 respectively). IMT could predict sildenafil responders more accurately than PSV, and the cut-off value of the IMT of the cavernous artery was less than 0.22 mm.

Erectile dysfunction and penile rehabilitation after pelvic fracture: a systematic review and meta-analysis

OBJECTIVE

To investigate the rate of erectile dysfunction (ED) after pelvic ring fracture (PRF).

DESIGN

Systematic review and meta-analysis.

METHODS

A systematic literature search of the Cochrane, EMBASE, MEDLINE, Scopus and Web of Science Library databases was conducted in January 2020. Included were original studies performed on humans assessing ED after PRF according to the 5-item International Index of Erectile Function (IIEF-5) questionnaire and fracture classification following Young and Burgess, Tile or Arbeitsgemeinschaft für Osteosynthesefragen/Orthopedic Trauma Association. Furthermore, interventional cohort studies assessing the effect of penile rehabilitation therapy with phosphodiesterase-5-inhibitors (PDE-5-I) on IIEF-5 scores compared before and after treatment were included. Results were presented as forest plots of proportions of patients with ED after PRF or mean changes on IIEF-5 questionnaires before and after penile rehabilitation. Studies not included in the quantitative analysis were narratively summarised. Risk of bias assessment was conducted using the revised tool for the Quality Assessment on Diagnostic Accuracy Studies.

RESULTS

The systematic literature search retrieved 617 articles. Seven articles were included in the qualitative analysis and the meta-analysis. Pooled proportions revealed 37% of patients with ED after suffering any form of PRF (result on probability scale pr=0.37, 95% CI: 0.26 to 0.50). Patients after 3 months of penile rehabilitation therapy reported a higher IIEF-5 score than before (change score=6.5 points, 95% CI: 2.54 to 10.46, p value=0.0013).

CONCLUSION

Despite some heterogeneity and limited high-quality research, this study concludes that patients suffering from any type of PRF have an increased risk of developing ED. Oral intake of PDE-5-I for the purpose of penile rehabilitation therapy increases IIEF-5 scores and may relevantly influence quality-of-life in these patients.

PROSPERO REGISTRATION NUMBER

CRD42020169699.

Repurposing of sildenafil as antitumour; induction of cyclic guanosine monophosphate/protein kinase G pathway, caspase-dependent apoptosis and pivotal reduction of Nuclear factor kappa light chain enhancer of activated B cells in lung cancer

OBJECTIVES

Lung cancer is one of the most frequent types of cancers that lead to death. Sildenafil is a potent inhibitor of phosphodiesterase-5 and showed potential anticancer effects, which has not yet been fully evaluated. Thus, this study aims to investigate the potential anticancer effect of sildenafil in urethane-induced lung cancer in BALB/c mice.

METHODS

Five-week-old male BALB/c mice were treated with either (i) normal saline only, (ii) sildenafil only 50 mg kg-1/ P.O every other day for the last four successive weeks, (iii) urethane 1.5 gm kg-1 i.p (at day 1 and day 60), (iv) carboplatin after urethane induction, or (v) sildenafil after urethane induction.

KEY FINDINGS

It was shown that sildenafil significantly increased the levels of cGMP and Caspase-3 with a reduction of NF-κB, Bcl-2, Cyclin D1, intercellular adhesion molecule 1, matrix metalloproteinase-2 levels and normalisation of Nrf2 along with pronounced improvement in the histological patterns.

CONCLUSIONS

These results indicated that sildenafil markedly induces cell cycle arrest, apoptosis and inhibits the metastatic activity through activation of cyclic guanosine monophosphate/protein kinase G pathway and down-regulation of cyclin D1 and nuclear factor kappa light chain enhancer of activated B cells with downstream anti-apoptotic gene Bcl-2, which underscores the critical importance of future using sildenafil in the treatment of lung cancer.

PDE-5 inhibitors in selected herbal supplements from the Ghanaian market for better erectile function as tested by a bioassay

Herbal supplements sold as 'all natural' on various markets in Accra (Ghana) and advertised as highly efficacious in treating erectile dysfunction (ED) were bought and analysed by a PDE-5 enzyme inhibition assay. The claimed efficacy of these products could be the result of inherent plant constituents, but also of intentionally added pharmaceuticals. Medically, ED is treated with potent inhibitors of the phosphodiesterase-5 (PDE-5) enzyme, as in the case of sildenafil. To test the efficacy of the Ghanaian supplements, extracts were made and tested using a PDE-Glo phosphodiesterase assay, a luminescent high-throughput screening (HTS) method. Results revealed that about 90% of the selected samples were able to inhibit PDE-5 activity to a high extent. Estimated concentrations in sildenafil equivalents ranged from traces to very high, with 25 samples (62.5%) pointing at daily doses higher than 25 mg sildenafil equivalents and 9 (22.5%) of these at doses higher than the maximal recommended daily intake of 100 mg sildenafil equivalents. Further investigations are needed to confirm if the observed effects are due to inherent plant constituents or merely the result of added synthetic PDE-5 enzyme inhibitors, especially because doses above 100 mg sildenafil equivalents per day may result in severe health risks.

Diketopiperazine-Based, Flexible Tadalafil Analogues: Synthesis, Crystal Structures and Biological Activity Profile

Phosphodiesterase 5 (PDE5) is one of the most extensively studied phosphodiesterases that is highly specific for cyclic-GMP hydrolysis. PDE5 became a target for drug development based on its efficacy for treatment of erectile dysfunction. In the present study, we synthesized four novel analogues of the phosphodiesterase type 5 (PDE5) inhibitor-tadalafil, which differs in (i) ligand flexibility (rigid structure of tadalafil vs. conformational flexibility of newly synthesized compounds), (ii) stereochemistry associated with applied amino acid building blocks, and (iii) substitution with bromine atom in the piperonyl moiety. For both the intermediate and final compounds as well as for the parent molecule, we have established the crystal structures and performed a detailed analysis of their structural features. The initial screening of the cytotoxic effect on 16 different human cancer and non-cancer derived cell lines revealed that in most cases, the parent compound exhibited a stronger cytotoxic effect than new derivatives, except for two cell lines: HEK 293T (derived from a normal embryonic kidney, that expresses a mutant version of SV40 large T antigen) and MCF7 (breast adenocarcinoma). Two independent studies on the inhibition of PDE5 activity, based on both pure enzyme assay and modulation of the release of nitric oxide from platelets under the influence of tadalafil and its analogues revealed that, unlike a reference compound that showed strong PDE5 inhibitory activity, the newly obtained compounds did not have a noticeable effect on PDE5 activity in the range of concentrations tested. Finally, we performed an investigation of the toxicological effect of synthesized compounds on Caenorhabditis elegans in the highest applied concentration of 6a,b and 7a,b (160 μM) and did not find any effect that would suggest disturbance to the life cycle of Caenorhabditis elegans. The lack of toxicity observed in Caenorhabditis elegans and enhanced, strengthened selectivity and activity toward the MCF7 cell line made 7a,b good leading structures for further structure activity optimization and makes 7a,b a reasonable starting point for the search of new, selective cytotoxic agents.

Role of application of tadalafil 5 mg once-daily (≥6 months) in men with erectile dysfunction from six randomized controlled trials

This meta-analysis was performed to assess the efficacy and safety of taking tadalafil 5 mg once-daily for at least 6 months in the treatment of erectile dysfunction (ED). Based on databases: MEDLINE, EMBASE and Cochrane Controlled Trials Register, this analysis was performed to collect randomized controlled trials (RCTs) of tadalafil 5mg once-daily in treating ED over 6 months. Reviewers also investigated the references of each literature. The meta-analysis covered a total of 1,596 patients in six RCTs. The tadalafil group performed a better effect in terms of the international index of erectile function-erectile function (IIEF) domain (P=0.005) for the treatment of ED compared with the placebo group. Safety assessments including discontinuations due to adverse events (AEs) (P=0.31) and treatment-emergent AEs (P=0.06) indicated that the tadalafil group had a better tolerate. The analysis elucidates that the dose of 5 mg per day of tadalafil showed a good effect after the treatment of at least 6 months relative to the control group with fewer side effects.

Suspected-target and non-targeted screenings of phosphodiesterase 5 inhibitors in herbal remedies using liquid chromatography-quadrupole time-of-flight-mass spectrometry

The lucrative market of herbal remedies spurs rampant adulteration, particularly with pharmaceutical drugs and their unapproved analogues. A comprehensive screening strategy is, therefore, warranted to detect these adulterants and, accordingly, to safeguard public health. This study uses the data-dependent acquisition of liquid chromatography-quadrupole time-of-flight-mass spectrometry (LC-QTOF-MS) to screen phosphodiesterase 5 (PDE5) inhibitors in herbal remedies using suspected-target and non-targeted strategies. For the suspected-target screening, we used a library comprising 95 PDE5 inhibitors. For the non-targeted screening, we adopted top-down and bottom-up approaches to flag novel PDE5 inhibitor analogues based on common fragmentation patterns. LC-QTOF-MS was optimised and validated for capsule and tablet dosage forms using 23 target analytes, selected to represent different groups of PDE5 inhibitors. The method exhibited excellent specificity and linearity with limit of detection and limit of quantification of <40 and 80 ng/mL, respectively. The accuracy ranged from 79.0% to 124.7% with a precision of <14.9% relative standard deviation. The modified, quick, easy, cheap, effective, rugged, and safe extraction provided insignificant matrix effect within -9.1%-8.0% and satisfactory extraction recovery of 71.5%-105.8%. These strategies were used to screen 52 herbal remedy samples that claimed to enhance male sexual performance. The suspected-target screening resulted in 33 positive samples, revealing 10 target analytes and 2 suspected analytes. Systematic MS and tandem MS interrogations using the non-targeted screening returned insignificant signals, indicating the absence of potentially novel analogues. The target analytes were quantified from 0.03 to 121.31 mg per dose of each sample. The proposed strategies ensure that all PDE5 inhibitors are comprehensively screened, providing a useful tool to curb the widespread adulteration of herbal remedies.

Efficacy and safety of oral phosphodiesterase 5 inhibitors for erectile dysfunction: a network meta-analysis and multicriteria decision analysis

PURPOSE

To quantitatively assess the benefit-risk ratio on the efficacy and safety of all phosphodiesterase type 5 inhibitors (PDE5i) in men with erectile dysfunction.

METHODS

A systematic review with network meta-analysis, surface under the cumulative ranking analysis and stochastic multicriteria acceptability analyses were performed. Searches were conducted in Pubmed, Scopus, Web of Science without limits for time-frame or language. Randomized controlled trials evaluating the efficacy or safety of any PDE5i compared to a placebo or to other PDE5i in males with erectile disfunction were included.

RESULTS

Overall, 184 articles representing 179 randomized controlled trials (50,620 patients) were included. All PDE5i were significantly more efficient than placebo. Sildenafil 25 mg was statistically superior to all interventions in enhancing IIEF (with a 98% probability of being the most effective treatment), followed by sildenafil 50 mg (80% of probability). Taladafil 10 mg and 20 mg also presented good profiles (73% and 76%, respectively). Avanafil and lodenafil were less effective interventions. Mirodenafil 150 mg was the treatment that caused more adverse events, especially flushing and headaches. Sildenafil 100 mg was more related to visual disorders, while vardenafil and udenafil were more prone to cause nasal congestion.

CONCLUSION

Sildenafil at low doses and tadalafil should be the first therapeutic options. Avanafil, lodenafil and mirodenafil use are hardly justified given the lack of expressive efficacy or high rates of adverse events.

Pharmacology and perspectives in erectile dysfunction in man

Penile erection is a perfect example of microcirculation modulated by psychological factors and hormonal status. It is the result of a complex neurovascular process that involves the integrative synchronized action of vascular endothelium; smooth muscle; and psychological, neuronal, and hormonal systems. Therefore, the fine coordination of these events is essential to maintain penile flaccidity or allow erection; an alteration of these events leads to erectile dysfunction (ED). ED is defined as the consistent or recurrent inability of a man to attain and/or maintain a penile erection sufficient for sexual activity. A great boost to this research field was given by commercialization of phosphodiesterase-5 (PDE5) inhibitors. Indeed, following the discovery of sildenafil, research on the mechanisms underlying penile erection has had an enormous boost, and many preclinical and clinical papers have been published in the last 10 years. This review is structured to provide an overview of the mediators and peripheral mechanism(s) involved in penile function in men, the drugs used in therapy, and the future prospective in the management of ED. Indeed, 30% of patients affected by ED are classified as "nonresponders," and there is still an unmet need for therapeutic alternatives. A flowchart suggesting the guidelines for ED evaluation and the ED pharmacological treatment is also provided.

Sildenafil and tadalafil reduce the risk of contrast-induced nephropathy by modulating the oxidant/antioxidant balance in a murine model

The aim of the study was to evaluate the potential protective role of sildenafil and tadalafil in contrast-induced nephropathy (CIN) by modulating oxidative stress. Thirty Wistar male rats were equally assigned into five groups: sham, CIN, CIN + sildenafil (10 mg/kg bw/day), CIN + tadalafil (5 mg/kg bw/day) and CIN + N-Acetyl Cysteine (NAC) (100 mg/kg bw/day) as a positive control. CIN was induced by 12 h dehydration and administration of indomethacin (10 mg/kg bw), N-ω- nitro-L-arginine methyl ester (10 mg/kg bw), and iopromide (3 g/kg bw iodine). Blood was drawn prior to and 24 h after CIN induction for evaluating renal function and oxidative stress. In the CIN group, total antioxidant capacity (TAC), reduced glutathione (GSH) and catalase (CAT) levels were significantly decreased; and protein carbonyl (PROTC) and thiobarbituric reactive species (TBARS) were significantly increased compared to the sham group. Pre- Sildenafil and tadalafil pre-treatment reduced CIN risk and reversed oxidative stress almost to the sham group levels. These results suggest that PDE5Is can be good candidates for preventing CIN based on their ability to modulate the oxidant/antioxidant balance.

Erectile Dysfunction: A Primer for in Office Management

Introduction: Optimizing erectile dysfunction (ED) remains a clinically significant endeavor as insufficient outcomes from oral, injectable and even surgical approaches to treatment remain less than ideal. In this report, we integrate evolving knowledge and provide an algorithmic approach for the clinician to fine-tune management. Methods: We performed a PubMed and Medline search of Erectile Dysfunction treatment optimization, enhanced patient efficacy for ED, and why men fail ED treatment. All relevant papers for the past two decades were reviewed. Results: Establishing the goals and objectives of the patient and partner while providing detailed instructions for treatment can minimize failures and create an environment that allows treatment optimization. A thorough work-up may identify reversible or contributing causes. We identified several areas where treatment of ED could be optimized. These include; management of associated medical conditions, lifestyle improvements, PDE5 inhibitor prescription strategies, management of hypogonadism and the initiation of intracavernosal injection therapy (ICI). Conclusions: In our view, once a man presents for help to the clinician, use of the simple strategies identified in this review to optimize the tolerability, safety and effectiveness of the selected treatment should result in enhanced patient and partner satisfaction, with improved outcomes.

When Healthcare Providers do not Ask, Patients Rarely Tell: The Importance of Sexual Counselling in Multiple Sclerosis

Multiple sclerosis (MS) is a relatively frequent inflammatory autoimmune illness of the central nervous system affecting about 2.5 million people around the world, and represents the most common cause of neurological disability among young adults. Indeed, the disease can affect sensory-motor, autonomic and cognitive function potentially leading to a high prevalence of sexual dysfunction (SD). Thus, the identification of barriers to help seeking for sexual concerns in patients with MS is an important, although still overlooked, issue. Aim of this overview is to briefly investigate the role of sexual counselling in managing SD in individuals with MS, highlighting the importance for the clinicians to get more knowledge about; the pathophysiology, assessment and treatment of MS-related SD.

[Cardiovascular safety of the recreational use of cannabis associated to sildenafil: Systematic review]

OBJECTIVES

The recreational use of drugs of abuse associated to therapeutically used drugs in sexual contexts forces the health care professional to know the possibility of drug-drug interactions among them. The aim of this review is updating the available information on cardiovascular safety of recreational use of sildenafil and cannabis.

MATERIALS AND METHODS

A systematic search in databases PubMed, PreMedline, Medline, Embase, ChemID, HSRPROJ, POPLINE and TOXLINE, from the start of the databases until to March 1, 2018 was made. Search terms were "sildenafil", "vardenafil", "tadalafil", "phosphodiesterase inhibitors" and "cannabis", combining and crossing them by means of Boolean operators with "adverse effects" and "cardiovascular". No restrictions for language or type of study were made.

RESULTS

Thirteen papers were found, 5out of them analyzed cannabis and sildenafil combination as a new style of recreational non-medical use. Only 3papers related sildenafil-cannabis association with cardiovascular events: one posterior myocardial infarction without Q wave, one myocardial infarction without ST elevation and one acute coronary syndrome.

CONCLUSIONS

Severity of sildenafil-cannabis-related cardiovascular events forces the healthcare professionals to take them into account and considering them in clinical pictures of an ischemic cardiomyopathy hard to classify.

Chronical treatment with sildenafil causes Achilles tendinopathy in rats

AIMS

The primary goal was to assess the effects of chronic sildenafil treatment over the Achilles tendons in rats.

MAIN METHODS

Animals were divided into two groups, control and sildenafil administration (n = 5). After 60 days, the tendons were subject to biochemical and image analysis to compare tendons between the groups: collagen I and decorin content, polarisation microscopy and birefringence analysis, and tissue zymography.

KEY FINDINGS

The animals exposed to sildenafil presented a much less organised tendon matrix, with reduced collagen I and non-collagenous protein content and a much higher decorin content.

SIGNIFICANCE

The results observed in the animals can be characterised as tendinopathy, a condition not yet described as a sildenafil side effect.

The pharmacist's role in improving the treatment of erectile dysfunction and its underlying causes

Erectile dysfunction (ED), which worldwide is likely to affect in excess of 300 million men by 2025, is often either untreated or insufficiently treated. It can be a prelude to other serious illnesses and may be a cause or consequence of depression in affected individuals. Among men younger than 60 years of age, ED can be a robust early-stage indicator of vascular disease and type 2 diabetes. Untreated or inadequately treated ED can also be a sign of poor communication between health professionals and service users of all ages. Improved treatment of ED could cost-effectively prevent premature deaths and avoidable morbidity. The extension of community pharmacy‒based health care would enable more men living with ED to safely access effective medications, along with appropriate diagnostic services and support for beneficial lifestyle changes such as smoking cessation in conveniently accessible settings. The task of introducing improved methods of affordably addressing problems linked to ED exemplifies the strategic challenges now facing health care systems globally. Promoting professionally supported self-care in pharmacies has the potential to meet the needs of aging populations in progressively more effective ways.

Phosphodiesterase (PDE5) inhibition assay for rapid detection of erectile dysfunction drugs and analogs in sexual enhancement products

Products marketed as dietary supplements for sexual enhancement are frequently adulterated with phosphodiesterase-5 (PDE5) inhibitors, which are erectile dysfunction drugs or their analogs that can cause adverse health effects. Due to widespread adulteration, a rapid screening assay was developed to detect PDE5 inhibitors in adulterated products. The assay employs fluorescence detection and is based on measuring inhibition of PDE5 activity, the pharmacological mechanism shared among the adulterants. Initially, the assay reaction scheme was established and characterized, followed by analysis of 9 representative PDE5 inhibitors (IC50 , 0.4-4.0 ng mL-1 ), demonstrating sensitive detection in matrix-free solutions. Next, dietary supplements serving as matrix blanks (n = 25) were analyzed to determine matrix interference and establish a threshold value; there were no false positives. Finally, matrix blanks were spiked with 9 individual PDE5 inhibitors, along with several mixtures. All 9 adulterants were successfully detected (≤ 5 % false negative rate; n = 20) at a concentration of 1.00 mg g-1 , which is over 5 times lower than concentrations commonly encountered in adulterated products. A major distinction of the PDE5 inhibition assay is the ability to detect adulterants without prior knowledge of their chemical structures, demonstrating a broad-based detection capability that can address a continuously evolving threat of new adulterants. The PDE5 inhibition assay can analyze over 40 samples simultaneously within 15 minutes and involves a single incubation step and simple data analysis, all of which are advantageous for combating the widespread adulteration of sex-enhancement products.

PDE5 inhibition eliminates cancer stem cells via induction of PKA signaling

Cancer stem cells (CSCs) are involved in metastasis and resistance development, thus affecting anticancer therapy efficacy. The underlying pathways required for CSC maintenance and survival are not fully understood and only a limited number of treatment strategies to specifically target CSCs have been identified. To identify novel CSC targeting compounds, we here set-up an aldehyde dehydrogenase (ALDH)-based phenotypic screening system that allows for an automated and standardized identification of CSCs. By staining cancer cells for ALDH activity and applying high-content-based single-cell population analysis, the proportion of a potential CSC subpopulation with significantly higher ALDH activity (ALDH_high) can be quantified in a heterogeneous cell population. We confirmed high ALDH activity as surrogate marker for the CSC subpopulation in vitro and validated Wnt signaling as an essential factor for the maintenance of CSCs in SUM149 breast cancer cells. In a small molecule screen, we identified phosphodiesterase type 5 (PDE5) inhibition as potential strategy to target CSC maintenance and survival in multiple cancer cell lines. CSC elimination by PDE5 inhibition was not dependent on PKG signaling, and we suggest a novel mechanism in which PDE5 inhibition leads to elevated cGMP levels that stimulate cAMP/PKA signaling to eliminate CSCs.

Use of phosphodiesterase type 5 inhibitors and risk of melanoma: a meta-analysis of observational studies

Background

Phosphodiesterase type 5 inhibitor (PE5i) administration may stimulate the proliferation and survival of melanocytes. However, discrepancies remain regarding the association between PDE5i use and melanoma risk in observational studies in humans.

Aim

To evaluate the association between PDE5i use and melanoma in a meta-analysis.

Materials and methods

Studies were identified by searching the PubMed and Embase databases. A random-effects model was applied to synthesize the data. A stratified study was performed to evaluate the influence of study characteristics on outcomes.

Results

Four prospective cohort studies and three case–control studies with 1,534,615 male participants and 16,053 melanoma cases were incorporated. Patients who received a PDE5i had a significantly increased risk for melanoma (adjusted risk ratio [RR] =1.12, 95% CI =1.03–1.33, P=0.008) with moderate heterogeneity (I²=54%). Cohort studies (adjusted RR =1.22, 95% CI =1.02–1.46, P=0.03) largely contributed to this result rather than case–control studies. Subsequent stratified analyses revealed that sildenafil was associated with an increased risk of melanoma (adjusted RR =1.26, 95% CI =1.07–1.50, P=0.007), but tadalafil and vardenafil were not. Also, PDE5i use was associated with a significantly increased risk of in situ melanoma (adjusted RR =1.31, 95% CI =1.01–1.69, P=0.04), but not of localized or nonlocalized melanoma.

Conclusion

PDE5i use may be associated with a significantly increased risk for melanoma in men. However, further research is needed to determine whether the association is causative.

Update on the Safety of Phosphodiesterase Type 5 Inhibitors for the Treatment of Erectile Dysfunction

INTRODUCTION

Phosphodiesterase type 5 inhibitors (PDE5Is) have demonstrated efficacy in the treatment of erectile dysfunction (ED). Although historically found to have limited drug-related adverse events, emerging data have suggested that PDE5Is might be associated with melanoma or recurrence of prostate cancer after radical prostatectomy.

AIM

To summarize the literature on the safety of PDE5Is.

METHODS

A literature review was performed through PubMed from 1990 through 2016 regarding ED. Keywords used for the search were erectile dysfunction, phosphodiesterase type 5 inhibitors, sildenafil, vardenafil, tadalafil, avanafil, safety, side effects, and adverse events, among others.

MAIN OUTCOME MEASURES

Visual, auditory, cardiovascular, renal, hepatic, priapic, and oncologic outcomes associated with the intake of PDE5Is for the treatment of ED, in addition to drug interactions, abuse, overdose, and the phenomenon of counterfeit medications.

RESULTS

PDE5Is are safe drugs for the management of ED. Although recent studies have shown an increased risk of non-arteritic ischemic optic neuropathy with PDE5Is, the magnitude of that risk is small. The possibility that PDE5Is cause sensorineural hearing loss remains uncertain. PDE5Is display a safe cardiovascular profile if used according to the Princeton III Consensus guidelines. There appears to be an association between PDE5I use and melanoma but the absence of a mechanism of causation raises doubt that the association is cause and effect. PDE5Is do not increase the risk of biochemical recurrence after prostate cancer management. PDE5I abuse and use of counterfeit medications present serious global health concerns.

CONCLUSION

Current data strongly support the efficacy, tolerability, and overall safety of PDE5Is for the treatment of ED. PDE5Is probably cause a small increase in the risk of non-arteritic ischemic optic neuropathy. Evidence on increased rates of melanoma and prostate cancer recurrence is weak and controversial. PDE5Is should still be considered first-line therapy for the treatment of most etiologies of ED. Yafi FA, Sharlip ID, Becher EF. Update on the Safety of Phosphodiesterase Type 5 Inhibitors for the Treatment of Erectile Dysfunction. Sex Med Rev 2018;6:242-252.

Direct comparison of tadalafil with sildenafil for the treatment of erectile dysfunction: a systematic review and meta-analysis

Aims

Erectile dysfunction (ED) is a major care problem worldwide. Tadalafil and sildenafil are the two most common phosphodiesterase 5 inhibitors used to treat ED. This systematic review and meta-analysis were conducted to directly compare tadalafil with sildenafil for the treatment of ED.

Methods

We designed a strategy for searching the PubMed, Embase, EBSCO, Web of Science and Cochrane library databases; the reference lists of the retrieved studies were also investigated. A literature review was performed to identify all published randomized or non-randomized controlled trials that compared tadalafil with sildenafil for the treatment of ED and to assess the quality of the studies. Two investigators independently and blindly screened the studies for inclusion. The meta-analysis was performed using RevMan 5.0.

Results

A total of 16 trials that compared tadalafil with sildenafil for the treatment of ED were included in the meta-analysis. In the meta-analysis, tadalafil and sildenafil appeared to have similar efficacies and overall adverse event rates. However, compared with sildenafil, tadalafil significantly improved psychological outcomes. Furthermore, the patients and their partners preferred tadalafil over sildenafil, and no significant difference was found in the adherence and persistence rates between tadalafil and sildenafil. Additionally, the myalgia and back pain rates were higher and the flushing rate was lower with tadalafil than with sildenafil.

Conclusion

Tadalafil shares a similar efficacy and safety with sildenafil and significantly improves patients’ sexual confidence. Furthermore, patients and their partners prefer tadalafil to sildenafil. Hence, tadalafil may be a better choice for ED treatment.

Medical treatment of erectile dysfunction: too many medical prescriptions?

Erectile dysfunction (ED) is a worldwide commonly reported condition; epidemiological data showed a prevalence ranging from 2.3 to 53.4% within different population subsets. In this context, the advent of phosphodiesterase type 5 inhibitors (PDE5is) in the second mid of 1990s has deeply changed the treatment scenario of this bothersome condition. Being user-friendly compounds with an excellent overall safety profile, PDE5is emerged as the first-line treatment for ED, thus overcoming topical alprostadil and intracavernous injections (ICIs). However, available data on treatment-utilization patterns and medical prescriptions of PDE5is showed a range of as wide as 22-78% of patients reporting to purchase PDE5is even without a proper medical prescription. Moreover, an increase in the recreational use of PDE5is among young men has been observed in the last decades, with a worrisome diffusion of potential health-risky behaviours associated with this habit. Indeed, treatment of ED should carefully follow internationally based clinical guidelines to avoid inappropriate drug prescriptions, which may eventually expose treated patients to drug-related side effects. Thereof, a careful assessment of the so-called modifiable and reversible ED risk factors along with a patient-tailored screening for potential contraindications to the treatment itself should be performed in every case. Lastly, although conclusive data still lack, the potential association between life-risky PDE5is side effects (i.e. cardiovascular adverse events, melanoma skin cancer and worsening of prostate cancer outcomes) should be carefully taken into account when counselling patients for ED treatment.

Innovative trends and perspectives for erectile dysfunction treatment: A systematic review

Objective

To review contemporary knowledge concerning the innovative trends and perspectives in the treatment of erectile dysfunction (ED).

Methods

Medline was reviewed for English-language journal articles between January 2000 and March 2016, using the terms ‘erectile dysfunction treatments’, ‘new trends’ and ‘perspectives’. In all, 114 original articles and 16 review articles were found to be relevant. Of the 76 cited papers that met the inclusion criteria, 51 papers had level of evidence of 1a–2b, whilst 25 had level of evidence of 3–4. Criteria included all pertinent review articles, randomised controlled trials with tight methodological design, cohort studies, and retrospective analyses. We also manually reviewed references from selected articles.

Results

Several interesting studies have addressed novel phosphodiesterase type 5 inhibitors (PDE5Is), orodispersible tablets, their recent chronic use, and combination with other agents. A few controlled studies have addressed herbal medicine as a sole or additional treatment for ED. Experimental studies and exciting review papers have addressed stem cells as novel players in the field of ED treatment. Other recent articles have revised the current status of low-intensity extracorporeal shockwave therapy in the field of ED. A few articles without long-term data have addressed new technologies that included: external penile support devices, penile vibrators, tissue engineering, nanotechnology, and endovascular tools for ED treatment.

Conclusions

The current treatment of ED is still far from ideal. We expect to see new drugs and technologies that may revolutionise ED treatment, especially in complex cases.