Clinical efficacy of a loading dose of naftopidil for patients with benign prostate hyperplasia

Prostate-to-bladder cross-sensitization in a model of zymosan-induced chronic pelvic pain syndrome in rats

BACKGROUND

The aim of the present study was to investigate the effects of chronic prostatitis/chronic pelvic pain syndrome (CP/CPPS) on bladder function and pathophysiology.

METHODS

To create a model for CPPS, rats were intraprostatically injected with zymosan or saline, serving as control. Metabolic cage experiments were performed 7, 14, or 21 days after zymosan injection and after 14 days in the control group. Thereafter, cystometry was performed in which simulated micturition cycles were induced by saline infusion and contractile responses to the cholinergic agonist methacholine and the purinergic agonist ATP were measured. Following cystometry, the prostate and urinary bladder were excised and assessed histopathologically for possible inflammatory changes.

RESULTS

Metabolic cage data revealed a significantly increased urinary frequency in zymosan treated rats. Likewise, the volume per micturition was significantly lower in all CPPS groups compared to controls. Cystometry showed a significant increase in the number of nonvoiding contractions, longer voiding time, and a trend towards lower compliance in CPPS rats compared to controls. Induction of CPPS led to significantly reduced cholinergic and purinergic contractile responses. Histopathological analysis demonstrated prostatic inflammation in all CPPS groups, in particular in later stage groups. Both the extent and grade of bladder inflammation were significantly higher in CPPS groups compared to controls.

CONCLUSIONS

The current findings demonstrate a potential prostate-to-bladder cross-sensitization leading to symptoms of bladder overactivity and signs of bladder inflammation. Future clinical studies are required to verify the outcomes of the current study and enable advancement of patient care.

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.

Bladder overactivity and afferent hyperexcitability induced by prostate-to-bladder cross-sensitization in rats with prostatic inflammation

KEY POINTS

There is clinical evidence showing that prostatic inflammation contributes to overactive bladder symptoms in male patients; however, little is known about the underlying mechanisms In this study, we investigated the mechanism that prostatic inflammation causes detrusor overactivity by using a rat model of chemically induced prostatic inflammation. We observed a significant number of dorsal root ganglion neurons with dichotomized afferents innervating both prostate and bladder. We also found that prostatic inflammation induces bladder overactivity and urothelial NGF overexpression in the bladder, both dependent on activation of the pelvic nerve, as well as changes in ion channel expression and hyperexcitability of bladder afferent neurons. These results indicate that the prostate-to-bladder cross-sensitization through primary afferent pathways in the pelvic nerve, which contain dichotomized afferents, could be an important mechanism contributing to bladder overactivity and afferent hyperexcitability induced by prostatic inflammation.

ABSTRACT

Prostatic inflammation is reportedly an important factor inducing lower urinary tract symptoms (LUTS) including urinary frequency, urgency and incontinence in patients with benign prostatic hyperplasia (BPH). However, the underlying mechanisms inducing bladder dysfunction after prostatic inflammation are not well clarified. We therefore investigated the effects of prostatic inflammation on bladder activity and afferent function using a rat model of non-bacterial prostatic inflammation. We demonstrated that bladder overactivity, evident as decreased voided volume and shorter intercontraction intervals in cystometry, was observed in rats with prostatic inflammation versus controls. Tissue inflammation, evident as increased myeloperoxidase activity, and IL-1α, IL-1β, and IL-6 levels inside the prostate, but not in the bladder, following intraprostatic formalin injection induced an increase in NGF expression in the bladder urothelium, which depended on activation of the pelvic nerve. A significant proportion (18-19%) of dorsal root ganglion neurons were double labelled by dye tracers injected into either bladder or prostate. In rats with prostatic inflammation, TRPV1, TRPA1 and P2X2 increased, and Kv1.4, a potassium channel α-subunit that can form A-type potassium (K_A ) channels, decreased at mRNA levels in bladder afferent and double-labelled neurons vs. non-labelled neurons, and slow K_A current density decreased in association with hyperexcitability of these neurons. Collectively, non-bacterial inflammation localized in the prostate induces bladder overactivity and enhances bladder afferent function. Thus, prostate-to-bladder afferent cross-sensitization through primary afferents in the pelvic nerve, which contain dichotomized afferents, could underlie storage LUTS in symptomatic BPH with prostatic inflammation.

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.

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.

Does Baseline Prostate Volume Affect the Short-Term Outcome of Tamsulosin?

OBJECTIVE

To investigate the short-term efficacy of tamsulosin treatment for patients with lower urinary tract symptoms (LUTS) suggestive of benign prostatic hyperplasia (BPH) according to baseline prostate volume (PV).

METHODS

Tamsulosin, 0.2 mg/day, was prospectively given to 112 patients aged 50 years or older who had International Prostate Symptom Scores (IPSS) ≥ 8. The short-term efficacy was analyzed using the IPSS, quality of life (QOL) index, BPH problem index (BPI), maximum flow rate (Qmax ) and postvoid residual urine volume (PVR) at 4 weeks and 3 months after treatment considering the estimated PV at baseline.

RESULTS

Of the 112 patients, 81 and 31 had PV of < 35 and ≥ 35 mL, respectively. The IPSS was significantly improved in patients with PV of < 35 mL (17.8 ± 5.9 at baseline, 13.5 ± 7.0 at 4 weeks, 11.9 ± 6.1 at 3 months) and in those with PV of ≥ 35 mL (17.4 ± 6.7 at baseline, 13.1 ± 7.0 at 4 weeks, 13.4 ± 6.2 at 3 months). There was no significant difference in the changes of the IPSS between the groups in a combined analysis model (P = 0.559). In addition, the model revealed no significant differences in changes in the QOL index, BPI, Qmax and PVR.

CONCLUSION

The short-term efficacy of tamsulosin is observed irrespective of baseline PV. Thus, α1-blocker monotherapy should be considered for all patients with BPH/LUTS to rapidly relieve symptoms, although the long-term outcome is not promising for patients with a large PV at baseline.

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.

The role of naftopidil in the management of benign prostatic hyperplasia

Naftopidil, which to a certain extent shows an affinity to α1D-adrenoceptor subtype in addition to a high affinity to α1A-adrenoceptor, has been used for the treatment of benign prostatic obstruction and benign prostatic hyperplasia (BPH) associated lower urinary tract symptoms (LUTS). The aim of the present review is to systematically refer to the published studies on this unique agent for BPH. Based on a randomized prazosin-controlled study and another double-blind placebo-controlled study, which verified the dose-dependent effects of naftopidil, the Japanese Ministry of Health, Labor and Welfare approved naftopidil for treating men with BPH in 1996. Several tamsulosin-controlled studies have suggested treatment effects of naftopidil similar to those of tamsulosin and potentially higher efficacy for alleviating storage symptoms by naftopidil. Although well-designed, randomized studies are warranted to confirm the long-term outcomes and effector/target of naftopidil, the α1A-antagonist naftopidil, which also blocks α1D-adrenoceptor, improves voiding symptoms, and may also be useful for the management of men with storage symptoms represented by nocturia, retrieving their quality of life impaired by BPH-associated LUTS.

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.

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

Naftopidil, approved only in Japan, is an α1-adrenergic receptor antagonist (α1-blocker) used to treat lower urinary tract symptoms (LUTS) suggestive of benign prostatic hyperplasia (BPH). Different from tamsulosin hydrochloride and silodosin, in that it has higher and extremely higher affinity respectively, for the α1A-adrenergic receptor subtype than for the α1D type, naftopidil has distinct characteristics because it has a three times greater affinity for the α1D-adrenergic receptor subtype than for the α1A subtype. Although well-designed large-scale randomized controlled studies are lacking and the optimal dosage of naftopidil is not always completely determined, previous reports from Japan have shown that naftopidil has superior efficacy to a placebo and comparable efficacy to other α1-blockers such as tamsulosin. On the other hand, the incidences of ejaculatory disorders and intraoperative floppy iris syndrome induced by naftopidil may be lower than for tamsulosin and silodosin having high affinity for the α1A-adrenergic receptor subtype. However, it remains unknown if the efficacy and safety of naftopidil in Japanese is applicable to white, black and Hispanic men having LUTS/BPH in western countries.

Clinical feature of men who benefit from dose escalation of naftopidil for lower urinary tract symptoms: a prospective study

Objectives. To examine the feature of men who benefit from dose escalation of naftopidil for lower urinary tract symptoms (LUTSs). Methods. Based on the IPSS, men reporting LUTS were prospectively studied using 50 mg/day of naftopidil for the first 4 weeks; satisfied patients continued its 50 mg/day (n = 11), and those reporting unsatisfactory improvement received its 75 mg/day (n = 35) for the next 4 weeks. Results. The 75 mg group showed improvement in the total IPSS and QOL score in a dose-dependent manner (at 4 weeks: P < .001, at 4 weeks versus 8 weeks: P < .05). In the 50 mg group, both scores reduced at 4 weeks, thereafter unchanged. The baseline slow stream score alone was higher in the 75 mg group (P = .013). The rate of change in the QOL score during the initial 4 weeks (ΔQOL) and Δnocturia was smaller in the 75 mg group (P < .05). Conclusions. Men with high slow stream score and unsatisfactory improvement in nocturia may benefit from dose escalation of naftopidil.