Naftopidil for the treatment of urinary symptoms in patients with benign prostatic hyperplasia

Comparative efficacy and safety of alpha-blockers as monotherapy for benign prostatic hyperplasia: a systematic review and network meta-analysis

Despite the availability of various drugs for benign prostatic hyperplasia (BPH), alpha(α)-blockers are the preferred first-line treatment. However, there remains a scarcity of direct comparisons among various α-blockers. Therefore, this network meta-analysis (NMA) of randomized controlled trials (RCTs) aimed to evaluate the efficacy and safety of α-blockers in the management of BPH. A comprehensive electronic search covered PubMed, Embase, Ovid MEDLINE, and Cochrane Library until August 2023. The primary endpoints comprised international prostate symptom score (IPSS), maximum flow rate (Qmax), quality of life (QoL), and post-void residual volume (PVR), while treatment-emergent adverse events (TEAEs) were considered as secondary endpoints. This NMA synthesized evidence from 22 studies covering 3371 patients with six kinds of α-blockers with 12 dose categories. IPSS has been considerably improved by tamsulosin 0.4 mg, naftopidil 50 mg and silodosin 8 mg as compared to the placebo. Based on the p-score, tamsulosin 0.4 mg had the highest probability of ranking for IPSS, PVR, and Qmax, whereas doxazosin 8 mg had the highest probability of improving QoL. A total of 297 adverse events were reported among all the α-blockers, silodosin has reported a notable number of TEAEs. Current evidence supports α-blockers are effective in IPSS reduction and are considered safer. Larger sample size with long-term studies are needed to refine estimates of IPSS, QoL, PVR, and Qmax outcomes in α-blocker users.

The Subtype Selectivity in Search of Potent Hypotensive Agents among 5,5-Dimethylhydantoin Derived α1-Adrenoceptors Antagonists

In order to find new hypotensive drugs possessing higher activity and better selectivity, a new series of fifteen 5,5-dimethylhydantoin derivatives (1-15) was designed. Three-step syntheses, consisting of N-alkylations using standard procedures as well as microwaves, were carried out. Crystal structures were determined for compounds 7-9. All of the synthesized 5,5-dimethylhydantoins were tested for their affinity to α1-adrenergic receptors (α1-AR) using both in vitro and in silico methods. Most of them displayed higher affinity (Ki < 127.9 nM) to α1-adrenoceptor than urapidil in radioligand binding assay. Docking to two subtypes of adrenergic receptors, α1A and α1B, was conducted. Selected compounds were tested for their activity towards two α1-AR subtypes. All of them showed intrinsic antagonistic activity. Moreover, for two compounds (1 and 5), which possess o-methoxyphenylpiperazine fragments, strong activity (IC50 < 100 nM) was observed. Some representatives (3 and 5), which contain alkyl linker, proved selectivity towards α1A-AR, while two compounds with 2-hydroxypropyl linker (11 and 13) to α1B-AR. Finally, hypotensive activity was examined in rats. The most active compound (5) proved not only a lower effective dose than urapidil but also a stronger effect than prazosin.

Hyperglycemia Induces Tear Reduction and Dry Eye in Diabetic Mice through the Norepinephrine-α1 Adrenergic Receptor-Mitochondrial Impairment Axis of Lacrimal Gland

Dry eye syndrome is a common complication in diabetic patients with a prevalence of up to 54.3%. However, the pathogenic mechanisms underlying hyperglycemia-induced tear reduction and dry eye remain less understood. The present study indicated that both norepinephrine (NE) and tyrosine hydroxylase levels were elevated in the lacrimal gland of diabetic mice, accompanied by increased Fos proto-oncogene (c-FOS)+ cells in the superior cervical ganglion. However, the elimination of NE accumulation by surgical and chemical sympathectomy significantly ameliorated the reduction in tear production, suppressed abnormal inflammation of the lacrimal gland, and improved the severity of dry eye symptoms in diabetic mice. Among various adrenergic receptors (ARs), the α1 subtype played a predominant role in the regulation of tear production, as treatments of α1AR antagonists improved tear secretion in diabetic mice compared with βAR antagonist propranolol. Moreover, the α1AR antagonist alfuzosin treatment also alleviated functional impairments of the meibomian gland and goblet cells in diabetic mice. Mechanically, the α1AR antagonist rescued the mitochondrial bioenergetic deficit, increased the mitochondrial DNA copy numbers, and elevated the glutathione levels of the diabetic lacrimal gland. Overall, these results deciphered a previously unrecognized involvement of the NE-α1AR-mitochondrial bioenergetics axis in the regulation of tear production in the lacrimal gland, which may provide a potential strategy to counteract diabetic dry eye by interfering with the α1AR activity.

Overcoming Drug Resistance in Advanced Prostate Cancer by Drug Repurposing

Prostate cancer (PCa) is the second most common cancer in men. Common treatments include active surveillance, surgery, or radiation. Androgen deprivation therapy and chemotherapy are usually reserved for advanced disease or biochemical recurrence, such as castration-resistant prostate cancer (CRPC), but they are not considered curative because PCa cells eventually develop drug resistance. The latter is achieved through various cellular mechanisms that ultimately circumvent the pharmaceutical’s mode of action. The need for novel therapeutic approaches is necessary under these circumstances. An alternative way to treat PCa is by repurposing of existing drugs that were initially intended for other conditions. By extrapolating the effects of previously approved drugs to the intracellular processes of PCa, treatment options will expand. In addition, drug repurposing is cost-effective and efficient because it utilizes drugs that have already demonstrated safety and efficacy. This review catalogues the drugs that can be repurposed for PCa in preclinical studies as well as clinical trials.

Evaluation of Alpha 1 Adrenoceptor Antagonist Dose Increase Therapy: An Essential Strategy for Patients with Lower Urinary Tract Symptoms Associated with Benign Prostatic Hyperplasia

Introduction

There have been a number of reports on dose increase therapy (DI-T) with the alpha 1 adrenoceptor antagonists (α1-blockers) naftopidil and tamsulosin for lower urinary tract symptoms associated with benign prostatic hyperplasia.

Methods and Results

The reports on DI-T (naftopidil 75 mg/d, tamsulosin 0.4 mg/d) in non-responders to low-dose initial therapy (LI-T, naftopidil 50 mg/d, tamsulosin 0.2 mg/d) were summarized. In each study, a non-responder was defined as a patient without sufficient improvements on the International Prostate Symptom Score (IPSS), IPSS Quality of Life, maximum flow rate of urine, or treatment satisfaction. These reports showed that 22.4-76.1% of patients were non-responders to LI-T, indicating that a novel treatment strategy for such patients is important. Moreover, 22.5-90.0% of non-responders to LI-T showed a response to DI-T, which achieved the same level of efficacy as low-dose maintenance therapy. Specifically, the improvements of the IPSS voiding symptom sub-score and maximum flow rate of urine were superior. The predictive factors for non-response to α1-blockers LI-T were insufficient improvement of subjective symptoms and objective findings during LI-T. These patients require high-dose initial therapy or DI-T at an early stage, since adverse events associated with naftopidil and tamsulosin do not show a dose-response relationship.

Conclusions

DI-T with α1-blockers has high potential as an essential treatment strategy for lower urinary tract symptoms associated with benign prostatic hyperplasia.

Drug Repositioning of the α1-Adrenergic Receptor Antagonist Naftopidil: A Potential New Anti-Cancer Drug?

Failure of conventional treatments is often observed in cancer management and this requires the development of alternative therapeutic strategies. However, new drug development is known to be a high-failure process because of the possibility of a lower efficacy than expected for the drug or appearance of non-manageable side effects. Another way to find alternative therapeutic drugs consists in identifying new applications for drugs already approved for a particular disease: a concept named "drug repurposing". In this context, several studies demonstrated the potential anti-tumour activity exerted by α1-adrenergic receptor antagonists and notably renewed interest for naftopidil as an anti-cancer drug. Naftopidil is used for benign prostatic hyperplasia management in Japan and a retrospective study brought out a reduced incidence of prostate cancer in patients that had been prescribed this drug. Further studies showed that naftopidil exerted anti-proliferative and cytotoxic effects on prostate cancer as well as several other cancer types in vitro, as well as ex vivo and in vivo. Moreover, naftopidil was demonstrated to modulate the expression of Bcl-2 family pro-apoptotic members which could be used to sensitise cancer cells to targeting therapies and to overcome resistance of cancer cells to apoptosis. For most of these anti-cancer effects, the molecular pathway is either not fully deciphered or shown to involve α1-adrenergic receptor-independent pathway, suggesting off target transduction signals. In order to improve its efficacy, naftopidil analogues were designed and shown to be effective in several studies. Thereby, naftopidil appears to display anti-cancer properties on different cancer types and could be considered as a candidate for drug repurposing although its anti-cancerous activities need to be studied more deeply in prospective randomized clinical trials.

Naftopidil for the treatment of lower urinary tract symptoms compatible with benign prostatic hyperplasia

BACKGROUND

Benign prostatic hyperplasia (BPH) is a common condition in ageing men that may cause lower urinary tract symptoms (LUTS). Treatment aims are to relieve symptoms and prevent disease-related complications. Naftopidil is an alpha-blocker (AB) that has a high affinity for the A1d receptor that may have advantages in treating LUTS in this setting. This is an update of a Cochrane Review first published in 2009. Since that time, several large randomised controlled trials (RCTs) have been reported, making this update relevant.

OBJECTIVES

To evaluate the effects of naftopidil for the treatment of LUTS associated with BPH.

SEARCH METHODS

We performed a comprehensive search using multiple databases (the Cochrane Library, MEDLINE, Embase, Scopus, LILAC, and Web of Science), trials registries, other sources of grey literature, and conference proceedings with no restrictions on the language of publication or publication status up to 31 May 2018 SELECTION CRITERIA: We included all parallel RCTs. We also included cross-over design trials.

DATA COLLECTION AND ANALYSIS

Two review authors independently classified and abstracted data from the included studies. We performed statistical analyses using a random-effects model and interpreted them according to the Cochrane Handbook for Systematic Reviews of Interventions. Primary outcomes were urological symptom scores, quality of life (QoL) and treatment withdrawals for any reason; secondary outcomes were treatment withdrawals due to adverse events, acute urinary retention, surgical intervention for BPH, and cardiovascular and sexual adverse events. We considered outcomes measured up to 12 months after randomisation as short term, and later than 12 months as long term. We rated the certainty of the evidence according to the GRADE approach.

MAIN RESULTS

We included 22 RCTs with 2223 randomised participants across four comparisons for short-term follow-up. This abstract focuses on only two of four comparisons for which we found data since two comparators (i.e. propiverine and Eviprostat (phytotherapy)) are rarely used. One study comparing naftopidil to placebo did not report any relevant outcomes and was therefore excluded. There were no trials that compared to combination therapy with naftopidil or any 5-alpha reductase inhibitors (5-ARIs) to combination therapy with other ABs and any 5-ARIs.All included studies were conducted in Asian countries. Study duration ranged from four to 12 weeks. Mean age was 67.8 years, prostate volume was 35.4 mL, and International Prostate Symptom Score was 18.3. We were unable to perform any of the preplanned subgroup analyses based on age and baseline symptom score.Naftopidil versus tamsulosinBased on 12 studies with 965 randomised participants, naftopidil may have resulted in little or no difference in urological symptom score (mean difference (MD) 0.47, 95% confidence interval (CI) -0.09 to 1.04 measured on a scale from 0 to 35 with higher score representing increased symptoms), QoL (MD 0.11, 95% CI -0.09 to 0.30; measured on a scale from 0 to 6 with higher scores representing worse QoL), and treatment withdrawals for any reason (risk ratio (RR) 0.92, 95% CI 0.64 to 1.34; corresponding to 7 fewer per 1000 participants, 95% CI 32 fewer to 31 more). Naftopidil may have resulted in little to no difference in sexual adverse events (RR 0.54, 95% CI 0.24 to 1.22); this would result in 26 fewer sexual adverse events per 1000 participants (95% CI 43 fewer to 13 more). We rated the certainty of evidence as moderate for urological symptom score and low for the other outcomes.Naftopidil versus silodosinBased on five studies with 652 randomised participants, naftopidil may have resulted in little or no difference in the urological symptom scores (MD 1.04, 95% CI -0.78 to 2.85), QoL (MD 0.21, 95% CI -0.23 to 0.66), and treatment withdrawals for any reason (RR 0.80, 95% CI 0.52 to 1.23; corresponding to 26 fewer per 1000 participants, 95% CI 62 fewer to 32 more). We rated the certainty of evidence as low for all these outcomes. Naftopidil likely reduced sexual adverse events (RR 0.15, 95% CI 0.06 to 0.42; corresponding to 126 fewer sexual adverse events per 1000 participants, 95% CI 139 fewer to 86 fewer). We rated the certainty of evidence as moderate for sexual adverse events.

AUTHORS' CONCLUSIONS

Naftopidil appears to have similar effects in the urological symptom scores and QoL compared to tamsulosin and silodosin. Naftopidil has similar sexual adverse events compared to tamsulosin but has fewer compared to silodosin.

Drug Repositioning for Effective Prostate Cancer Treatment

Drug repositioning has gained attention from both academia and pharmaceutical companies as an auxiliary process to conventional drug discovery. Chemotherapeutic agents have notorious adverse effects that drastically reduce the life quality of cancer patients so drug repositioning is a promising strategy to identify non-cancer drugs which have anti-cancer activity as well as tolerable adverse effects for human health. There are various strategies for discovery and validation of repurposed drugs. In this review, 25 repurposed drug candidates are presented as result of different strategies, 15 of which are already under clinical investigation for treatment of prostate cancer (PCa). To date, zoledronic acid is the only repurposed, clinically used, and approved non-cancer drug for PCa. Anti-cancer activities of existing drugs presented in this review cover diverse and also known mechanisms such as inhibition of mTOR and VEGFR2 signaling, inhibition of PI3K/Akt signaling, COX and selective COX-2 inhibition, NF-κB inhibition, Wnt/β-Catenin pathway inhibition, DNMT1 inhibition, and GSK-3β inhibition. In addition to monotherapy option, combination therapy with current anti-cancer drugs may also increase drug efficacy and reduce adverse effects. Thus, drug repositioning may become a key approach for drug discovery in terms of time- and cost-efficiency comparing to conventional drug discovery and development process.

Human UDP-Glucuronosyltransferase 2B4 and 2B7 Are Responsible for Naftopidil Glucuronidation in Vitro

Naftopidil (NAF) is widely used for the treatment of benign prostatic hyperplasia and prevention of prostate cancer in elderly men. These patients receive a combination of drugs, which involves high risk for drug–drug interaction. NAF exhibits superior efficacy but must be administered at a much higher dosage than other therapeutic drugs. We previously showed that extensive glucuronidation of NAF enantiomers caused poor bioavailability. However, the metabolic pathway and mechanism of action of NAF enantiomer remain to be elucidated. The present study was performed to identify the human UDP-glucuronosyltransferases (UGTs) responsible for the glucuronidation of NAF enantiomers and to investigate the potential inhibition of UGT activity by NAF. The major metabolic sites examined were liver and kidney, which were compared with intestine. Screening of 12 recombinant UGTs showed that UGT2B7 primarily contributed to the metabolism of both enantiomers. Moreover, enzyme kinetics for R(+)-NAF, UGT2B7 (mean K_m, 21 μM; mean V_max, 1043 pmol/min/mg) showed significantly higher activity than observed for UGT2B4 and UGT1A9. UGT2B4 (mean K_m, 55 μM; mean V_max, 1976 pmol/min/mg) and UGT2B7 (mean K_m, 38 μM; mean V_max, 1331 pmol/min/mg) showed significantly higher catalysis of glucuronidation of S(-)-NAF than UGT1A9. In human liver microsomes, R(+)-NAF and S(-)-NAF also inhibited UGT1A9: mean K_i values for R(+)-NAF and S(-)-NAF were 10.0 μM and 11.5 μM, respectively. These data indicate that UGT2B7 was the principal enzyme mediating glucuronidation of R(+)-NAF and S(-)-NAF. UGT2B4 plays the key role in the stereoselective metabolism of NAF enantiomers. R(+)-NAF and S(-)-NAF may inhibit UGT1A9. Understanding the metabolism of NAF enantiomers, especially their interactions with metabolic enzymes, will help to elucidate potential drug–drug interactions and to optimize the administration of this medicine.

The predictive factors of α1-D/A adrenoceptor antagonist, naftopidil, dose increase therapy for male lower urinary tract symptoms caused by benign prostatic hyperplasia: INFORM study

Introduction:

We evaluated the predictive factors which affect the efficacy of naftopidil 50 mg/day therapy and dose increase therapy to administration of 75 mg/day after an initial dose of 50 mg/day.

Materials and Methods:

A total of 92 patients with male lower urinary tract symptoms/benign prostatic hyperplasia were administrated naftopidil 50 mg/day for 4 weeks (50 mg therapy). At week 4, the patients were divided into an effective and an ineffective group (Group E and Group I, respectively). For further 4 weeks, the dosage of naftopidil was increased to 75 mg/day in all patients. At week 8, the patients of Group E and Group I were divided into an effective and an ineffective group (Group EE, Group EI, Group IE, and Group II, respectively).

Results:

Postvoid residual (PVR) urine volume at baseline was a predictive factor for efficacy of 50 mg therapy. In Group E, change in International Prostate Symptom Score storage symptoms subscore from baseline to week 4 was a predictive factor for efficacy of this dose increase therapy. In Group I, change in maximum flow rate from baseline to week 4 was a predictive factor for efficacy of this dose increase therapy.

Conclusions:

The short term of naftopidil 50 mg therapy was ineffective for the patients who had large PVR. The predictive factor of this dose increase therapy might be a dynamic variable in 50 mg/day of dose period, but not a baseline variable at the time of 75 mg/day dosage starts.

Drug interactions between antiretrovirals and drugs used to treat benign prostatic hyperplasia/lower urinary tract symptoms

INTRODUCTION

Significant advances in antiretroviral (ARV) therapy have transformed HIV into a chronic manageable disease. Co-morbidities associated with aging, such as benign prostatic hyperplasia (BPH), are becoming increasingly prevalent in the HIV-infected population. The pharmacological treatment of BPH involves medications mainly metabolized by CYP 450 enzymes, while many ARVs have inducing or inhibiting effects on the CYP 450 system. Consequently, there is potential for significant pharmacokinetic (PK) interactions between these two classes of medications.

AREAS COVERED

This article reviews the pharmacology and metabolism of selected BPH drug therapies and ARVs, in addition to highlighting potential interactions between these two drug categories. The authors also present PK evidence of interactions from available clinical trials, product monographs and international conference abstracts. Potentially significant drug interactions are summarized and strategies for management are discussed.

EXPERT OPINION

Drugs most likely to interact with BPH medications include protease inhibitors, the non-nucleoside reverse transcriptase inhibitors efavirenz, nevirapine, etravirine, and the cobicistat-boosted integrase inhibitor elvitegravir. Clinically significant PK interactions with BPH medications and dolutegravir, raltegravir, rilpivirine, or the investigational agent doravirine do not appear to exist. Clinicians working with HIV-infected individuals need to recognize the potential for interactions involving BPH and ARV treatments to ensure effective and safe drug therapy use.

Does prostate volume affect the efficacy of α1D/A: Adrenoceptor antagonist naftopidil?

Introduction:

There have been reports that one of the factors affecting the efficacy of α1-adrenoceptor antagonists (α1-blocker; α1-B) was prostate volume (PV). However, there are few reports of short-term prospective trials comparing the efficacy of α1-B by PV. We examined the influence of PV on the short-term efficacy of naftopidil dose increase therapy to administration of 75 mg/day after an initial dose of 50 mg/day.

Materials and Methods:

A total of 85 patients with lower urinary tract symptoms associated with benign prostatic hyperplasia (LUTS/BPH) received 50 mg/day of naftopidil for 4 weeks. After 4 weeks, the dosage of naftopidil was increased to 75 mg/day for a further 4 weeks. We divided the patients into two groups of PV ≥40 mL at baseline (Group L) and PV <40 mL at baseline (Group S).

Results:

International Prostate Symptom Score (IPSS), IPSS storage symptoms, and IPSS quality-of-life score were significantly improved at 4 and 8 weeks compared with baseline in both Groups. IPSS voiding symptoms (IPSS-VS) were significantly improved at 4 and 8 weeks compared with baseline in Group S. IPSS and IPSS-VS were significantly improved at 8 weeks compared with 4 weeks only in Group L. IPSS-VS and intermittency at 4 weeks were significantly decreased in Group S compared with Group L. Maximum flow rate was significantly improved at 8 weeks compared with baseline in Group L.

Conclusions:

PV is a predictive factor affecting the efficacy of naftopidil 50 mg/day for IPSS-VS, and the dose increase to 75 mg/day effective for IPSS-VS. A total of 50 mg/day of naftopidil is the maintenance dose for LUTS/BPH patients with a small PV, and 75 mg/day of dose increase therapy should be chosen for patients with a large PV.

Three-year outcome analysis of alpha 1-blocker naftopidil for patients with benign prostatic hyperplasia in a prospective multicenter study in Japan

PURPOSE

Our aim was to prospectively analyze the 3-year outcomes of naftopidil treatment for patients with benign prostatic hyperplasia (BPH), including those who dropped out during follow-up and had retreatment for BPH after termination of the drug within 3 years.

PATIENTS AND METHODS

Naftopidil, 50 mg/d or 75 mg/d, was given to 117 patients having BPH aged 50 years and older who had international prostate symptom scores (IPSS) ≥8. They were prospectively followed for 3 years with periodic evaluation. If naftopidil was terminated, the reason was determined. For patients with termination, an outcome survey was done to evaluate the status of retreatment for BPH at 3 years.

RESULTS

Twenty-five patients (21.4%) continued the same medication for 3 years. The total IPSS, quality of life index, BPH problem index, and maximum flow rate were significantly improved during 3 years. Treatment failure defined as symptomatic progression (an increase in the IPSS of ≥4 points compared to the baseline value), development of acute urinary retention, conversion to other α1-blockers, add-on of a 5α-reductase inhibitor, or conversion to surgery was observed in 41 patients (35.0%). In the univariate analysis, age, prostate volume, and serum prostate-specific antigen were predictors of treatment failure. Of the 50 patients who discontinued naftopidil during the follow-up, only 13 (26%) patients reported that they needed retreatment with α1-blockers and/or surgery within 3 years.

CONCLUSION

Long-term efficacy of naftopidil was observed, although older age, increased prostate volume, and elevated prostate-specific antigen at baseline were highly likely to result in treatment failure. Even after termination for various reasons, only a small portion of the patients needed retreatment for BPH within 3 years.

A synopsis of drugs currently in preclinical and early clinical development for the treatment of benign prostatic hyperplasia

INTRODUCTION

Benign prostatic hyperplasia (BPH) is a common disease among men and significantly impacts quality of life by causing lower urinary tract symptoms (LUTS). Current medical therapies are not always adequate in controlling LUTS or slowing disease progression, and there is unmet need for new effective therapeutic options.

AREAS COVERED

The authors review the standard current medical therapies for BPH which include the use of α-1 blockers, 5-α reductase inhibitors, combination therapy and PDE inhibitors. Following this, the authors then discuss new therapies that are currently undergoing preclinical and clinical investigation.

EXPERT OPINION

Existing preclinical and clinical trials have highlighted many promising therapies to treat BPH. Further investigation with larger clinical trials is needed to establish these drugs as standard therapies. As the number of drugs in the arsenal against BPH continues to grow, providers and patients will have to engage in a discussion that weighs the risks and benefits of each therapy.

Enantiospecific determination of naftopidil by RRLC-MS/MS reveals stereoselective pharmacokinetics and tissue distributions in rats

Naftopidil (NAF) is used as a racemate to treat benign prostatic hyperplasia (BPH) and to prevent prostate cancer. However, racemic NAF has low bioavailability; therefore, it is commonly administered at higher clinical dosages compared to other therapeutic BPH drugs. Differences in interactions between individual enantiomers and biological macromolecules may result in variations in pharmacokinetics and dispositions. This study aimed to investigate the pharmacokinetics, bioavailability and tissue distributions of NAF enantiomers in rats after intragastric administration of the individual enantiomers. A rapid and sensitive liquid chromatography coupled with triple-quadrupole mass spectrometric method (RRLC-MS/MS) was developed and validated for determination of NAF enantiomers in rat plasma, tissues, urine and feces. After intragastric administration, S(-)-NAF in plasma [maximum concentration (C(max)) = 186.4 ng/mL, area under the curve from 0 h to 24h (AUC(0-24 h)) = 877.9 ng h/mL] was significantly higher than that of R(+)-NAF (C(max) = 133.2 ng/mL, AUC(0-24 h) = 602.1 ng h/mL). Moreover, S(-)-NAF bioavailability was twice that of R(+)-NAF. R(+)-NAF distributions in the prostate, liver, and kidney were significantly higher than S(-)-NAF distributions (R/S ratios of 3.16, 1.33, and 2.90, respectively). These data reveal the stereoselective pharmacokinetic profiles of the two enantiomers in rats.

A comparison of the efficacy of naftopidil and tamsulosin hydrochloride in medical treatment of benign prostatic enlargement

Introduction:

Lower urinary tract symptoms in men, over age of 50 years is suggestive of benign prostatic enlargement (BPE). Different alpha-blockers have been evaluated for the treatment of benign prostatic hyperplasia for over last 30 years. This study was conducted in a tertiary care institution during the period of year between June 2011 and August 2013 to compare the effect of naftopidil and tamsulosin in reducing the obstructive and irritable symptoms of BPE.

Subjects and Methods:

A prospective randomized comparative study was carried on 60 patients of BPE by assigning half of them to treatment with tamsulosin and rest with naftopidil. Pre- and post-treatment uroflowmetry (UFM), post-void residue (PVR), International Prostate Symptoms Score (IPSS), were obtained at 15 and 30 days after starting treatment.

Results:

The age of patients ranged from 51 to 78. At base line there was no statistical difference between UFM parameter, PVR and IPSS in the two groups. UFM and PVR showed significantly better response at both intervals with naftopidil. Comparison of IPSS showed better improvement in Group A both at 15 and 30 days. It was seen that the obstructive symptoms showed a significantly better response with tamsulosin and symptoms of irritability was seen better response with naftopidil.

Conclusion:

It was seen that during the period of follow-up of 30 days naftopidil had a better effect on UFM, PVR, IPSS compared with tamsulosin. In general, obstructive symptoms showed better improvement in tamsulosin and irritative symptoms showed better improvement in naftopidil.

Comparative evaluation of naftopidil and tamsulosin in the treatment of patients with lower urinary tract symptoms with benign prostatic hyperplasia

INTRODUCTION

Naftopidil, approved initially in Japan, is an α1d-adrenergic receptor antagonist (α1-blocker) used to treat lower urinary tract symptoms (LUTS) due to benign prostatic hyperplasia (BPH). It is different from tamsulosin hydrochloride and silodosin, in that it has a higher affinity for the α1D-adrenergic receptor subtype than for the α1A subtype and has a superior efficacy to a placebo and comparable efficacy to other α1-blockers such as tamsulosin. The incidences of ejaculatory disorders and intraoperative floppy iris syndrome induced by naftopidil may also be lower than that for tamsulosin and silodosin, which have a high affinity for the α1A-adrenergic receptor subtype. However, it remains unknown if the efficacy and safety of naftopidil in Japanese men is applicable to Indian men having LUTS/BPH.

MATERIAL AND METHODS

Two groups of 60 patients each, having LUTS due to BPH, were treated with tamsulosin 0.4 mg and Naftopidil 75 mg for three months. Ultrasonography (for prostate size, post-void residual volume), uroflowmetry, and the International Prostate Symptom Score (IPSS) and Quality of Life (QOL) score were recorded at the beginning of the study, and then at one and three months.

RESULTS

The prostate size, post-void residual volume, all the uroflowmetry variables, and the IPSS QOL scores showed a statistically significant improvement (P < 0.001) in both the groups. The improvement in the average flow rate and the QOL index was better in the naftopidil group on the intergroup comparison and was statistically significant (P < 0.001).

CONCLUSION

Although the QOL life index was significantly better in the naftopidil group, overall both naftopidil and tamsulosin were found to be equally effective in the treatment of LUTS due to BPH.

Current role of treatment in men with lower urinary tract symptoms combined with overactive bladder

Lower urinary tract symptoms (LUTS) and benign prostatic hyperplasia (BPH) are highly prevalent in older men. The storage subcategory of LUTS is synonymous with overactive bladder (OAB) syndrome, which is an empirical diagnosis. Traditionally, alpha-blockers are widely prescribed to manage the LUTS of BPH, although storage symptoms may persist in many men despite treatment. Therefore, because therapies that target the prostate often fail to alleviate storage symptoms, they may not be the appropriate therapy for OAB. In past years, most physicians appeared to give more weight in elderly men to voiding symptoms than to storage symptoms and to be more concerned with initial treatment with anticholinergics for males with storage symptoms. Considering the recent increase in data on the efficacy and safety of combination treatment with alpha receptor antagonists and antimuscarinic agents, the standard pharmacologic treatment of patients with LUTS combined with OAB should be an alpha receptor antagonist and an antimuscarinic agent. Beta-3 adrenoreceptor agonists may also potentially be useful for the treatment of male LUTS combined with OAB.

Identification of human cytochrome P450 isozymes involved in the metabolism of naftopidil enantiomers in vitro

Objectives

Naftopidil (NAF) is a chiral compound with two enantiomers (R(+)-NAF and S(−)-NAF) and is used as a racemic mixture in clinical practice. This study aims to investigate the metabolism of NAF enantiomers in pooled human liver microsomes (HLMs) and cytochrome P450 isozymes (CYPs) involved in their metabolism.

Methods

Metabolism studies were conducted in vitro using HLMs. Specific chemical inhibitors and recombinant human CYPs were used to confirm that the CYPs contributed to the metabolism of NAF enantiomers.

Key findings

Three metabolites were found and characterized in the HLMs incubations from R(+)-NAF and S(−)-NAF, respectively. The major metabolic pathways of R(+)-NAF and S(−)-NAF were demethylation and hydroxylation. CYP2C9 and CYP2C19 inhibitors strongly inhibited R(+)-NAF metabolism, and CYP1A2, CYP2C8, CYP2D6 and CYP3A4/5 inhibitors moderately inhibited R(+)-NAF metabolism. CYP2C9 inhibitors strongly inhibited S(−)-NAF metabolism, and CYP2C8, CYP2C19 and CYP3A4/5 inhibitors moderately inhibited S(−)-NAF metabolism. Consistent with the results of chemical inhibitors experiments, recombinant human CYP2C9 and CYP2C19 contributed greatly to R(+)-NAF metabolism, and CYP2C9 contributed greatly to S(−)-NAF metabolism.

Conclusion

Both R(+)-NAF and S(−)-NAF are metabolized to three metabolites in HLMs. CYP2C9 plays the most important role in the demethylation and hydroxylation of both NAF enantiomers, CYP2C19 is another major CYP isoform that is involved in R(+)-NAF metabolism.

Naftopidil for the treatment of benign prostate hyperplasia: a systematic review

OBJECTIVES

The aim of the study was to systematically review the effects of the adrenoreceptor A1D antagonist naftopidil in the management of lower urinary tract symptoms (LUTS).

METHODS

A structured and comprehensive MEDLINE search was conducted for original articles, reviews, and metanalyses assessing the clinical pharmacology as well as the safety of naftopidil in the treatment of LUTS secondary to BPH. English-language publications dating from 1950 to 2013 were considered.

RESULTS

In the considered timeframe, 14 randomized clinical trials (RCT) were reported. Overall, the outcome measures assessed in the various reports included in the present review were changes from baseline in: International Prostate Symptom Score (IPSS), quality of life (QoL) score, maximum urinary flow rate (Qmax), residual volume (PVR), and adverse effects. Although additional well designed, worldwide, placebo-controlled and randomized studies are necessary to confirm the long-term outcomes of naftopidil pharmacotherapy, current data suggest that naftopidil administration in BPH patients provides comparable improvements in total IPSS, QoL, and urinary symptoms from baseline relative to 0.2 mg/d tamsulosin and 8 mg/d silodosin. However, improvements in Qmax are generally less with naftopidil than with tamsulosin. Reported adverse effects related to naftopidil administration are negligible and usually mild.

CONCLUSION

It remains unknown whether the data reported on naftopidil in the Japanese population are applicable in symptomatic BPH patients from western countries given that: (1) no English-language clinical trials have compared naftopidil to placebo in Western countries; (2) all clinical trials available were carried out in Japan; (3) in the comparative studies with tamsulosin, the dose of this drug was lower than the recommended dose in Western countries; (4) no data from long-term clinical trials evaluating drug safety beyond 18 weeks.

α1D/A-adrenoceptor antagonist naftopidil for the male lower urinary tract symptoms associated with benign prostatic hyperplasia: efficacy of dose increase therapy

OBJECTIVES

To examine the efficacy of dose increase therapy in patients with lower urinary tract symptoms associated with benign prostatic hyperplasia who responded poorly to 50 mg/day of naftopidil.

METHODS

A total of 95 patients received 50 mg/day of naftopidil for 8 weeks. After this treatment period, they were divided into two groups: the poor responders were defined as those who either had an International Prostate Symptom Score-Quality of Life ≥ 4 or with an International Prostate Symptom Score-Quality of Life of 3 whose International Prostate Symptom Score-Quality of Life improved <2 points (group A). All other patients were defined as responders to naftopidil 50 mg/day (group B). The dose of naftopidil was increased to 75 mg/day in group A, and maintained at 50 mg/day in group B. The treatment was continued for a further 8 weeks.

RESULTS

The prostate volume at the baseline was significantly larger in group A than group B. The improvement of International Prostate Symptom Score total score, International Prostate Symptom Score-Quality of Life, and voided volume after 8 weeks was significantly better in group B than in group A. However, there was no significant difference in the changes of all parameters between the two groups after 16 weeks.

CONCLUSIONS

A dose increase to 75 mg/day is an effective treatment strategy in patients with lower urinary tract symptoms associated with benign prostatic hyperplasia who responded poorly to an initial dose of 50 mg/day of naftopidil. Furthermore, a starting dose of 75 mg/day should be considered in patients with a large prostate volume, as this is a predictive factor for dose increase.

Anti-androgenic effects of S-40542, a novel non-steroidal selective androgen receptor modulator (SARM) for the treatment of benign prostatic hyperplasia

BACKGROUND

Selective androgen receptor modulators (SARMs) would provide alternative therapeutic agent for androgen-related diseases. We identified a tetrahydroquinoline (THQ) derivative, 1-(8-nitro-3a, 4, 5, 9b-tetrahydro-3H-cyclopenta[c]quinolin-4-yl) ethane-1, 2-diol (S-40542) as a novel SARM antagonist.

METHODS

Affinity for nuclear receptors of S-40542 was evaluated in receptor-binding studies. Androgen receptor (AR) transcriptional activity of S-40542 was investigated by luciferase reporter assay in DU145AR cells. Normal and benign prostatic hyperplasia (BPH) model rats were repeatedly treated with S-40542 and flutamide. The tissue weights of prostate and levator ani muscle as well as blood levels of testosterone and luteinizing hormone were measured.

RESULTS

S-40542 bound to the AR with high affinity. S-40542 at relatively high concentrations increased the transcriptional activity. This agent also showed a concentration-dependent AR antagonistic action in the presence of 1 nM 5α-dihydrotestosterone. Repeated treatment with S-40542 and flutamide decreased dose-dependently the weights of the prostate to a similar extent. In contrast, the tissue weight-reducing effect by S-40542 treatment on the levator ani muscle was much weaker than that of flutamide. S-40542 had little effect on the blood level of testosterone and luteinizing hormone, whereas flutamide increased the level of both hormones. Furthermore, S-40542 decreased dose-dependently prostate weight of BPH rats.

CONCLUSIONS

The current results indicate that S-40542 possesses the prostate-selective SARM activity, suggestive of clinical benefit against benign prostate hyperplasia. THQ compounds may be useful for the research of mode of action of SARMs and for the development of safe SARM antagonists.