Effects of an alpha-1d adrenoreceptor antagonist (naftopidil) on bladder dysfunction after radiotherapy in female rats.

PURPOSE: Storage-phase bladder dysfunction can develop after pelvic radiotherapy. As the alpha-1d adrenoreceptor (a1d-AR) is dominant in the human detrusor, we aimed to investigate the effect of an a1d-AR antagonist on bladder dysfunction after pelvic radiotherapy in a rat model. MATERIALS AND METHODS: Twenty-four female Wistar rats were used. Eight rats (14-15 weeks, 250-300 g) were randomized to three groups (normal reference group, radiation alone group and radiation plus naftopidil group). An 18-Gy dose of radiotherapy was applied to the radiation alone and radiation plus naftopidil groups. Naftopidil (20 mg/kg) was administered daily to the radiation plus naftopidil group. Four weeks after radiation, all rats underwent cystometry and were killed for reverse transcription polymerase chain reaction to detect mRNAs [a1d-AR, brain-derived neurotrophic factor (BDNF) and vascular endothelial growth factor (VEGF)], Western blot to detect proteins (a1d-AR, extracellular-signal-regulated kinase, BDNF and VEGF) and immunohistochemistry. RESULTS: Compared to the radiation alone group, (1) the decrease in the mRNA and protein expression of a1d-AR and VEGF was ameliorated, (2) the increase in the expression of BDNF mRNA and proteins such as extracellular-signal-regulated kinase and BDNF was suppressed, (3) submucosal thickness and vascularity on immunohistochemistry were improved, and (4) the baseline intravesical pressure and intercontraction interval in cystometry were ameliorated in the radiation plus naftopidil group. CONCLUSION: Administration of an a1d-AR antagonist could improve storage-phase bladder dysfunction after radiotherapy not only by upregulating a1d-AR, which might decrease bladder compliance, but also by enhancing vascularity, which might protect the urinary bladder from chronic ischemic inflammation.

Outcomes and complications of naftopidil versus tamsulosin for elderly men with lower urinary tract symptoms secondary to benign prostatic hyperplasia: A systematic review and meta-analysis.

We conducted a systematic review and meta-analysis to assess the outcomes and complications of naftopidil in treating elderly men with lower urinary tract symptoms secondary to benign prostatic hyperplasia and compared them with those administered with tamsulosin. A literature review was performed to identify the available randomised controlled trials concerning the comparison between naftopidil and tamsulosin for men with LUTS/BPH. We searched the following databases: the Cochrane Library Database, PubMed, Embase and Web of Science. Eleven publications involving 1,114 men (557 in the naf group and 557 in the tam group) were pooled in our analysis. We found no significant differences in the total IPSS, IPSS storage score, IPSS voiding score, quality of life index, peak urinary flow rate, average flow rate and post-void residual volumes. We assessed cardiovascular and sexual adverse events, acute urinary retention, surgical intervention, withdrawals due to any reason and withdrawals due to adverse events. The incidence of adverse events was similar among patients in naf and tam groups. In conclusion, naftopidil shared comparable efficacy and similar incidence of adverse events with tamsulosin and appears to be a promising agent for and alternative to tam. However, more prospective trials with high quality and long-term treatment duration are needed to verify this observation.

Analyses of the Mode of Action of an Alpha-Adrenoceptor Blocker in Substantia Gelatinosa Neurons in Rats.

To elucidate why naftopidil increases the frequency of spontaneous synaptic currents in only some substantia gelatinosa (SG) neurons, post-hoc analyses were performed. Blind patch-clamp recording was performed using slice preparations of SG neurons from the spinal cords of adult rats. Spontaneous inhibitory and excitatory postsynaptic currents (sIPSCs and sEPSCs, respectively) were recorded. The ratios of the frequency and amplitude of the sIPSCs and sEPSCs following the introduction of naftopidil compared with baseline, and after the application of naftopidil, serotonin (5-HT), and prazosin, compared with noradrenaline (NA) were evaluated. First, the sIPSC analysis indicated that SG neurons reached their full response ratio for NA at 50 µM. Second, they responded to 5-HT (50 µM) with a response ratio similar to that for NA, but prazosin (10 µM) did not change the sEPSCs and sIPSCs. Third, the highest concentration of naftopidil (100 µM) led to two types of response in the SG neurons, which corresponded with the reactions to 5-HT and prazosin. These results indicate that not all neurons were necessarily activated by naftopidil, and that the micturition reflex may be regulated in a sophisticated manner by inhibitory mechanisms in these interneurons.

Identification of HUHS190, a human naftopidil metabolite, as a novel anti-bladder cancer drug.

We carried out structure-activity relationship study on anti-cancer effects of naftopidil (1) and its metabolites, resulted in identification of 1-(4-hydroxy-2-methoxyphenyl)piperazin-1-yl)-3-(naphthalen-1-yloxy) propan-2-ol (2, HUHS190), a major human metabolite of 1, which exhibited the most selective toxicities between against normal and cancer cells (Table 1). 2 was more hydrophilic compared to 1, was enough to be prepared in high concentration solution of more than 100 µM in saline for an intravesical instillation drug. Moreover, serum concentration of 2 was comparable to that of 1, an oral preparation drug, after oral administration at 32 mg/kg (Fig. 3). Both of 1 and 2 showed broad-spectrum anti-cancer activities in vitro, for example, 1 and 2 showed inhibitory activity IC50 = 21.1 µM and 17.2 µM for DU145, human prostate cancer cells, respectively, and IC50 = 18.5 µM and 10.5 µM for T24 cells, human bladder cancer cells. In this study, we estimated anticancer effects of 2 in a bladder cancer model after intravesical administration similar to clinical cases. A single intravesical administration of 2 exhibited the most potent inhibitory activities among the clinical drugs for bladder cancers, BCG and Pirarubicin, without obvious side effects and toxicity (Fig. 4). Thus, HUHS190 (2) can be effective for patients after post-TURBT therapy of bladder cancer without side effects, unlike the currently available clinical drugs.

Long-term administration of alpha-1 blocker can reverse the micturition pattern in a bladder outlet obstruction murine model.

OBJECTIVE: To investigate the effect of chronic administration of an alpha-1 blocker on micturition patterns in long-term partial bladder outlet obstruction. METHODS: Mice were divided into three groups: a normal group, in which animals were fed a standard diet; a partial bladder outlet obstruction group, in which the proximal urethra was tied and animals were fed a standard diet; and a partial bladder outlet obstruction + naftopidil group, in which the proximal urethra was tied and animals were fed a standard diet containing naftopidil. Micturition behavior was evaluated in all groups for 6 months after partial bladder outlet obstruction surgery. The parameters evaluated included voided volume, time per void, urination frequency and total urine volume. Quantitative assessment of gene expression was also carried out. RESULTS: Total urine volume, as well as total and average voided volume during night, was significantly decreased in partial bladder outlet obstruction + naftopidil mice compared with partial bladder outlet obstruction animals. The levels of transcripts encoding 5-hydroxytryptamine 2A and tissue inhibitor of metalloproteinase 2 were significantly decreased in the partial bladder outlet obstruction + naftopidil group compared with the partial bladder outlet obstruction group. CONCLUSIONS: Long-term administration of an alpha-1 blocker seems to reverse the disturbance of the micturition pattern caused by partial bladder outlet obstruction. Mechanistically, this effect might be mediated by changes in the expression of a serotonin receptor and/or in the activity of the fibrogenesis pathway.

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.

α1 -Blocker inhibits non-voiding contractions and decreases the level of intravesical prostaglandin E2 in rats with partial bladder outlet obstruction.

OBJECTIVES: To elucidate the mechanism of action of the α1 -blocker, naftopidil, in partial bladder outlet obstruction animals, by studying non-voiding contractions, and the levels of mediators were measured with resiniferatoxin treatment. METHODS: A total of 35 female Wistar rats were randomly divided into a sham or bladder outlet obstruction group, and rats in each group were given vehicle or resiniferatoxin. Incomplete urethral ligation was applied to the bladder outlet obstruction group. After cystometry, the intravesical level of prostaglandin E2 and adenosine 5'-triphosphate was measured in the instilled perfusate collected. Naftopidil was given at the time of cystometry. RESULTS: In bladder outlet obstruction rats, non-voiding contractions, bladder capacity, and the intravesical levels of prostaglandin E2 and adenosine 5'-triphosphate were markedly increased compared with sham rats. Naftopidil decreased non-voiding contractions, enlarged the bladder capacity, and decreased the intravesical levels of prostaglandin E2 and adenosine 5'-triphosphate. Resiniferatoxin enhanced non-voiding contractions. The effects of naftopidil on non-voiding contractions and the intravesical level of prostaglandin E2 , but not adenosine 5'-triphosphate, were tolerant to resiniferatoxin. CONCLUSIONS: In bladder outlet obstruction rats, one cause of generation of non-voiding contractions might be bladder wall distension, but not transient receptor potential cation channel V1. The increase in intravesical prostaglandin E2 might also be associated with the generation of non-voiding contractions. Naftopidil inhibits the increase in non-voiding contractions and decreases the intravesical level of prostaglandin E2 , which are independent of transient receptor potential cation channel V1.

Comparison of Silodosin and Naftopidil for Efficacy in the Treatment of Benign Prostatic Enlargement Complicated by Overactive Bladder: A Randomized, Prospective Study (SNIPER Study).

PURPOSE: We investigated the efficacy of 2 α1-blockers with different affinities for the α1-adrenoceptor subtypes silodosin and naftopidil in the treatment of benign prostatic enlargement complicated by overactive bladder. MATERIALS AND METHODS: This was a prospective, open label, randomized, multicenter study of 350 outpatients with untreated benign prostatic enlargement associated with urinary urgency at least once per week and an OABSS (Overactive Bladder Symptom Score) of 3 or greater. Patients were randomly assigned to receive silodosin 8 mg per day or naftopidil 75 mg per day. Changes in parameters from baseline to 4 and 12 weeks were assessed based on I-PSS (International Prostate Symptom Score), I-PSS quality of life, OABSS and voiding functions measured by uroflowmetry. RESULTS: On efficacy analysis a total of 314 patients were included in the 2 groups. No significant difference in adverse effects was observed between the groups. Mean I-PSS and I-PSS quality of life scores, and OABSS significantly improved in both groups. Statistically significantly greater improvement in the silodosin group than in the naftopidil group was observed in total OABSS (p = 0.03), I-PSS quality of life score (p = 0.005) and OABSS urgency score (p <0.001) at 12 weeks. In regard to voiding function the maximum urinary flow rate showed significant improvements in both groups but the change in the maximum flow rate in the silodosin group at 12 weeks was significantly greater than in the naftopidil group (3.6 vs 2.1 ml per second). CONCLUSIONS: Silodosin, a pure α1A-adrenoceptor blocker, showed greater improvement in overactive bladder symptoms along with the urinary flow rate in patients with benign prostatic enlargement complicated by overactive bladder compared to naftopidil, an α1D>A-adrenoceptor blocker.

Action of naftopidil on spinal serotonergic neurotransmission for inhibition of the micturition reflex in rats.

AIMS: We examined the mechanism of action of naftopidil, an α1D/A blocker, on spinal descending serotonergic neurotransmission for the micturition reflex. METHODS: We examined (1) urinary 5-hydroxyindole acetic acid (5-HIAA) after intraperitoneal administration of saline, para-chlorophenylalanine (PCPA; a serotonin synthetic enzyme inhibitor), and/or 5-hydroxytryptophan (5-HTP; a serotonin precursor); (2) isovolumetric cystometry after intraperitoneal administration of saline, PCPA, and/or 5-HTP and intravenous injection of naftopidil; and (3) isovolumetric cystometry before and after intrathecal administration of serotonin (5-HT) receptor antagonists and intravenous injection of naftopidil. RESULTS: PCPA decreased and 5-HTP increased urinary 5-HIAA/creatinine. Intraperitoneal injection of PCPA did not influence cystometric parameters. Intraperitoneal injection of 5-HTP significantly shortened the interval between bladder contractions. Intravenous injection of naftopidil transiently abolished bladder contractions. However, the duration of abolishment of bladder contractions after injection of naftopidil in rats given PCPA was significantly shorter than that in rats given vehicle, but significantly longer than that in rats given PCPA and 5-HTP. Intrathecal injection of 5-HT1B, 5-HT3, or 5-HT7 receptor antagonists significantly prolonged the interval between bladder contractions. Intrathecal injection of 5-HT1D or 5-HT2B receptor antagonists significantly shortened the interval between bladder contractions. Combined administration of the maximum non-effective dose of 5-HT1D, 5-HT2A, 5-HT2B, 5-HT2C, or 5-HT3 receptor antagonists and intravenous injection of naftopidil significantly shortened the duration of abolishment of bladder contraction compared to intravenous injection of naftopidil alone. CONCLUSIONS: Naftopidil may inhibit the micturition reflex via 5-HT1D, 5-HT2A, 5-HT2B, 5-HT2C, and 5-HT3 receptors in the spinal cord. Neurourol. Urodynam. 36:604-609, 2017. © 2016 Wiley Periodicals, Inc.

Effects of an alpha1A/D-adrenoceptor antagonist, naftopidil, and a phosphodiesterase type 5 inhibitor, tadalafil, on urinary bladder remodeling in rats with spinal cord injury.

AIMS: In order to clarify whether an alpha1A/D-adrenoceptor (α1 A/D-AR) antagonist, naftopidil, or a phosphodiesterase type 5 (PDE5) inhibitor, tadalafil, prevents bladder wall remodeling after spinal cord injury (SCI), we examined the bladder and urethral activity as well as ischemic and fibrotic changes in the bladder using SCI rats with or without naftopidil or tadalafil treatment. METHODS: Adult female Sprague-Dawley rats were divided into four groups: (1) normal (spinal cord intact); (2) vehicle SCI; (3) naftopidil SCI; and (4) tadalafil SCI groups. In SCI groups, rats underwent Th9-10 spinal cord transection followed by oral application of vehicle, naftopidil (20 mg/kg/day) or tadalafil (2 mg/kg/day) for 1, 2, 4, 8, and 12 weeks. Bladder and urethral pressures, mRNA levels of fibrosis-related molecules and ischemia markers and the composition of bladder collagen and elastin were evaluated. RESULTS: Naftopidil treatment reduced the upregulation of mRNA levels of ischemia and fibrosis markers at the early phase of SCI, and ameliorated the decrease of bladder compliance and voiding efficiency, and the increase of urethral pressure and collagen concentration in the bladder wall at the late phase of SCI. Tadalafil treatment reduced the upregulation of mRNA levels of fibrosis markers, the decrease of bladder compliance and the increase of collagen concentration at the late phase of SCI. CONCLUSIONS: These results suggest that naftopidil and tadalafil treatments improved the bladder remodeling shown by increased bladder collagen contents after SCI in a different time course. Thus, these treatments could be effective for reducing the SCI-related tissue remodeling in the bladder. Neurourol. Urodynam. 9999:XX-XX, 2016. © 2016 Wiley Periodicals, Inc.

Silodosin versus naftopidil in the treatment of premature ejaculation: A prospective multicenter trial.

OBJECTIVES: To determine the efficacy of two α1-adrenoceptor antagonists with different affinities for α1-adrenoceptor subtypes, silodosin and naftopidil, in the treatment of premature ejaculation. METHODS: This was a prospective, open-label, multicenter trial. A total of 26 patients with untreated acquired premature ejaculation were enrolled. Premature ejaculation was defined based on the International Society for Sexual Medicine recommendation. Patients self-administered on demand silodosin 4 mg or naftopidil 25 mg 1 h before intercourse, alternating drugs at least three times each. Clinical global impression change for premature ejaculation, premature ejaculation profile, and intravaginal ejaculation latency time were evaluated at baseline and during treatment. RESULTS: Due to clinical global impression change, 24 patients (92%) and 12 patients (46%) reported improvement in their own premature ejaculation problems under silodosin and nafitopidil administration, respectively. Silodosin treatment produced a significantly higher improvement rate compared with naftopidil (P = 0.0002). Objectively, silodosin significantly prolonged intravaginal ejaculation latency time compared with baseline and naftopidil (P < 0.01). Mean intravaginal ejaculation latency times were 1.9, 4.1, and 7.6 min at baseline, control and with silodosin, respectively. The rate of reduced semen volume during silodosin treatment was higher than during naftopidil treatment. There were no adverse systemic effects in either group. CONCLUSIONS: Silodosin, a highly selective α1A-adrenoceptor antagonist, produces greater improvements in premature ejaculation profiles and related symptoms along with intravaginal ejaculation latency time in acquired premature ejaculation patients with or without erectile dysfunction. This result supports the clinical use of silodosin as an alternative treatment for premature ejaculation.

Effect of naftopidil on brain noradrenaline-induced decrease in arginine-vasopressin secretion in rats.

Naftopidil, an α1-adrenoceptor antagonist, has been shown to inhibit nocturnal polyuria in patients with lower urinary tract symptom. However, it remains unclear how naftopidil decreases nocturnal urine production. Here, we investigated the effects of naftopidil on arginine-vasopressin (AVP) plasma level and urine production and osmolality in rats centrally administered with noradrenaline (NA). NA (3 or 30 µg/kg) was administered into the left ventricle (i.c.v.) of male Wistar rats 3 h after naftopidil pretreatment (10 or 30 mg/kg, i.p.). Blood samples were collected from the inferior vena cava 1 h after NA administration or 4 h after peritoneal administration of naftopidil; plasma levels of AVP were assessed by ELISA. Voiding behaviors of naftopidil (30 mg/kg, i.p.)-administered male Wistar rats were observed during separate light- and dark cycles. Administration of NA decreased plasma AVP levels and elevated urine volume, which were suppressed by systemic pretreatment with naftopidil (30 mg/kg, i.p.). Urine osmolality decreased 1 h after NA administration. However, naftopidil by itself had no effect on plasma AVP levels or urodynamic parameters during light- and dark cycles. Our findings suggest that systemic administration of naftopidil could prevent central noradrenergic nervous system-mediated decline in AVP secretion and increase in urine production in rats.

Molecularly imprinted polymeric stir bar: Preparation and application for the determination of naftopidil in plasma and urine samples.

In this study, molecularly imprinting technology and stir bar absorption technology were combined to develop a microextraction approach based on a molecularly imprinted polymeric stir bar. The molecularly imprinted polymer stir bar has a high performance, is specific, economical, and simple to prepare. The obtained naftopidil-imprinted polymer-coated bars could simultaneously agitate and adsorb naftopidil in the sample solution. The ratio of template/monomer/cross-linker and conditions of template removal were optimized to prepare a stir bar with highly efficient adsorption. Fourier transform infrared spectroscopy, scanning electron microscopy, selectivity, and extraction capacity experiments showed that the molecularly imprinted polymer stir bar was prepared successfully. To utilize the molecularly imprinted polymer stir bar for the determination of naftopidil in complex body fluid matrices, the extraction time, stirring speed, eluent, and elution time were optimized. The limits of detection of naftopidil in plasma and urine sample were 7.5 and 4.0 ng/mL, respectively, and the recoveries were in the range of 90-112%. The within-run precision and between-run precision were acceptable (relative standard deviation <7%). These data demonstrated that the molecularly imprinted polymeric stir bar based microextraction with high-performance liquid chromatography was a convenient, rapid, efficient, and specific method for the precise determination of trace naftopidil in clinical analysis.

Naftopidil versus flopropione as medical expulsive therapy for distal ureteral stones: results of a randomized, multicenter, double-blind, controlled trial.

PURPOSE: A multicenter, double-blind, randomized, controlled trial was conducted to determine the efficacy of naftopidil as medical expulsive therapy (MET) for patients with distal ureteral stones. METHODS: Ninety-two patients presenting with a single distal ureteral stone ≤10 mm were randomly assigned to receive either naftopidil (75 mg of naftopidil once in the morning and placebo twice a day) or flopropione (80 mg three times a day). The primary end point was time to stone expulsion calculated by the Kaplan-Meier method. Secondary end points were the percentages of patients who required analgesics, hospital admission, and surgery, the number of working days lost to the disease, and treatment safety. RESULTS: Overall, three patients were excluded from the final analysis. No significant differences were noted in age, stone size, and stone side between the treatment arms. The median time to stone expulsion was 8 days [95 % confidence interval (CI), 3-16] for the naftopidil group, and this was significantly less than the 18 days (95 % CI, 11 to not reached) for the flopropione group (p = 0.03). On multivariate Cox regression analysis, the hazard of expulsion was 1.8-fold higher for the naftopidil group than for the flopropione group after adjustment for age, sex, stone side, and stone size. No significant differences were noted in the secondary end points. CONCLUSIONS: The administration of naftopidil significantly improved time to stone expulsion in patients with distal ureteral stones ≤10 mm. We believe that this is the first multicenter, double-blind, randomized, controlled trial demonstrating the efficacy of naftopidil for MET.

Efficacy of naftopidil for nocturia in male patients with lower urinary tract symptoms: comparison of morning and evening dosing.

OBJECTIVES: To examine the difference in improvement of lower urinary tract symptoms between morning and evening dosing of α1 -blocker naftopidil. METHODS: A total of 177 male patients with nocturia were included in the present study and randomized to morning or evening dosing of naftopidil. The International Prostate Symptom Score, quality of life index and nocturia quality of life index were compared between the two study groups at 12 weeks. RESULTS: A total of 143 patients (morning group: n = 70, evening group: n = 73) were analyzed as a result of the dropout of 34 patients because of failure to give consent, adverse events and failure to attend. Nocturia, quality of life index and nocturia quality of life index at 12 weeks were significantly better in the evening group compared with the morning group. In a multivariate model, both the dosing time of naftopidil and the initial nocturia quality of life index were significantly associated with change in nocturia quality of life index. CONCLUSIONS: Evening dosing of naftopidil seems to be more effective in treating nocturia in male patients with lower urinary tract symptoms.

Simultaneous stereoselective analysis of naftopidil and O-desmethyl naftopidil enantiomers in rat feces using an online column-switching high-performance liquid chromatography method.

A novel online column-switching chiral high-performance liquid chromatography method was developed and validated for the simultaneous determination of naftopidil (NAF) and its O-desmethyl metabolites (DMN) enantiomers in rat feces. Direct and multiple injections of supernatant from rat feces homogenate were allowed through the column-switching system. Analyte extraction was performed on the Capcell Pak mixed-functional column by acetonitrile-phosphate buffer (pH 7.4; 10 mm; 8:92, v/v) flowing at 1 mL/min. Separation of NAF and DMN enantiomers was achieved on the Chiralpak IA column by methanol-acetonitrile-acetate buffer (pH 5.3; 5 mm; 45:33:22, v/v/v) flowing at 0.5 mL/min. The analytes were measured with a fluorescence detector at 290 nm (λ(ex)) and 340 nm (λ(em)). The validated method showed a good linearity [22.5-15,000 ng/mL for (+)-/(-)-NAF; 35-25,000 ng/mL for (+)-/(-)-DMN] and the lowest limits of quantification for NAF and DMN enantiomers were 22.5 and 35 ng/mL, respectively. Both intra- and inter-day variations were <10%. The assay was successfully applied to the fecal excretion of NAF and DMN enantiomers in rat after single oral administration of (±)-NAF. Nonstereoselective excretion of (+)- and (-)-NAF was found in feces, while stereoselective excretion of (+)- and (-)-DMN was observed with higher excretion levels of (+)-DMN, indicating that there may exist stereoselective metabolism for NAF enantiomers.

Silodosin versus naftopidil in Japanese patients with lower urinary tract symptoms associated with benign prostatic hyperplasia: a randomized multicenter study.

OBJECTIVES: Silodosin is a novel drug that is highly selective to subtype alpha 1A and, since 2006, has been used in Japan for treating benign prostatic hyperplasia. This study aimed to compare the clinical effects of the alpha-adrenoceptor antagonist, silodosin, with those of naftopidil in patients presenting lower urinary tract symptoms associated with benign prostatic hyperplasia. METHODS: This was a randomized, open-label, controlled multicenter study carried out in Japan. Overall, 121 participants with lower urinary tract symptoms associated with benign prostatic hyperplasia were randomized to receive silodosin (4 mg twice daily) or naftopidil (50 mg once daily) for 4 or 8 weeks. Patients were divided into four groups: the alpha-blocker-naive groups received silodosin (35 patients) or naftopidil (33 patients) and the drug-switching groups changed from tamsulosin to silodosin (26 patients) or naftopidil (27 patients). The outcomes parameters were the International Prostate Symptom Score, quality of life, maximum urinary flow rate and post-void residual urine volume. P < 0.05 was considered statistically significant by using the Wilcoxon signed-rank and rank-sum tests, and analysis of covariance. RESULTS: In all the groups, silodosin and naftopidil significantly improved the total International Prostate Symptom Score and quality of life. However, silodosin obtained significantly better improvement in total International Prostate Symptom Score in the alpha-blocker-naive patients at 4 and 8 weeks. The maximum urinary flow rate and residual urine did not change significantly in all the treatment groups. CONCLUSIONS: The present study confirms the clinical usefulness of silodosin in the treatment of lower urinary tract symptoms associated with benign prostatic hyperplasia.

Reduction of prostate cancer incidence by naftopidil, an α1 -adrenoceptor antagonist and transforming growth factor-ß signaling inhibitor.

OBJECTIVES: Quinazoline-based α(1) -adrenoceptor antagonists are known to inhibit prostate tumor growth through induction of apoptosis. We investigated the effect of a naphthalene-based α(1) -adrenoceptor antagonist, naftopidil, on prostate cancer incidence, apoptosis of prostatic cell and transforming growth factor-ß signaling. METHODS: Prescription records were linked to pathological data for men who continued naftopidil (n = 766) or tamsulosin (n = 1015) for 3 months or longer between 2003 and 2010. Prostate cancer incidence was analyzed by log-rank test and the Cox proportional hazards model. Apoptosis and cell cycle arrest in human tissues were assessed by immunohistochemical detection of Bcl2 and p21, respectively. Growth inhibition and apoptosis treatment with naftopidil and tamsulosin were assessed in cancer cell lines. Interference with transforming growth factor-ß signaling was examined by western blot analysis. RESULTS: Prostate cancer incidence was significantly lower in men who received naftopidil for 3 months or longer compared with tamsulosin (P = 0.035). Multivariate analysis confirmed a decreased hazard ratio, 0.46, for naftopidil use (P = 0.013), which was more evident with longer treatment. Immunohistochemical positivity for Bcl2, a marker for resistance to apoptosis, was less frequently detected in prostate cancer cells of men who received naftopidil compared with tamsulosin (P < 0.05). Naftopidil inhibited cancer cell growth, induced apoptosis and blocked Smad2 phosphorylation activated by transforming growth factor-ß in cell lines, with a half maximal inhibitory concentration of 1.1 µmol/L. CONCLUSIONS: Naftopidil seems to reduce prostate cancer incidence, possibly by inducing apoptosis, preferentially in cancer cells, and blocking transforming growth factor-ß signaling.

Association of silodosin, tamsulosin, and naftopidil with delirium: analysis of the pharmacovigilance database in Japan.

BACKGROUND: An association between adrenergic alpha-1 receptor antagonists and delirium has been suggested, but the details are unclear. AIM: This study investigated the association between adrenergic alpha-1 receptor antagonists and delirium in patients with benign prostatic hyperplasia using the Japanese Adverse Drug Event Report database. METHOD: First, disproportionality analysis compared the frequency of delirium in the adrenergic alpha-1 receptor antagonists silodosin, tamsulosin, and naftopidil. Next, multivariate logistic analysis was performed to examine the association between delirium and adrenergic alpha-1 receptor antagonists where disproportionality was detected. RESULTS: A disproportionality in delirium was observed in patients receiving tamsulosin (reporting odds ratio [ROR] 1.85, 95% confidence interval [CI] 1.38-2.44, P < 0.01) compared with those who did not, and also in patients receiving naftopidil (ROR 2.23, 95% CI 1.45-3.28, P < 0.01) compared with those who did not. Multivariate logistic analysis revealed that in addition to previously reported risk factors for delirium, delirium in patients receiving tamsulosin was significantly increased with concomitant use of anticholinergics (odds ratio 2.73, 95% CI 1.41-5.29, P < 0.01) and delirium in patients receiving naftopidil was significantly increased with concomitant use of beta3-adrenergic receptor agonists (odds ratio 4.19, 95% CI 1.66-10.6, P < 0.01). CONCLUSION: Anticholinergics or beta3-adrenergic receptor agonists to treat overactive bladder in patients receiving tamsulosin and naftopidil was strongly associated with delirium. Confirming the medical history and concomitant medications of patients receiving tamsulosin or naftopidil may contribute to preventing delirium in patients with benign prostatic hyperplasia and to improving their outcomes.

Naftopidil enantiomers suppress androgen accumulation and induce cell apoptosis via the UDP-glucuronosyltransferase 2B15 in benign prostate hyperplasia.

Accumulation of androgens mediate alterations in prostate growth and has emerged as an essential factor in benign prostate hyperplasia (BPH). Dihydrotestosterone (DHT), the most potent natural androgen, binds to androgen receptors (AR) and regulates the prostate growth. Many inhibitors of DHT synthesis have been developed to reduce DHT levels and used in the treatment of prostate diseases. However, therapies targeting the elimination of the DHT remain limited. The DHT in prostate is metabolized by UDP-glucuronosyltransferase 2B (UGT2B) and transforms into inactive products. In this study, we analyzed and demonstrated that two enantiomers of naftopidil (NAF), an α1D/1A-adrenoceptor blocker, induced expression and activity of UGT2B in BPH rat prostate models as well as UGT2B15 in human prostate cells, BPH-1. The NAF enantiomers reduced intraprostatic and intracellular DHT levels, thus promoting cell apoptosis. Besides, assays with siRNA UGT2B15 transfection showed that UGT2B15 played an essential role in mediating the effects of the NAF enantiomers. The UGT2B15 mediated the inhibition of AR and PSA expression by NAF enantiomers. The data showed that the mechanism of upregulating UGT2B15 by the NAF enantiomers might differ from that of AR antagonists and 5α-reductase inhibitors. Together, our results demonstrated that NAF enantiomers could be potential and novel UGT2B15 regulators, which accelerated the DHT elimination and promoted apoptosis of BPH-1 cells. This study could help expand the clinical application of NAF and support the development of new therapeutic strategies targeting the elimination of androgens for the treatment of BPH and other androgen-sensitive diseases.