Clinical effect of alpha 1D/A adrenoceptor inhibitor naftopidil on benign prostatic hyperplasia: an international prostate symptom score and King's Health Questionnaire assessment

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.

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 effect of naftopidil on the quality of life of patients with lower urinary tract symptoms suggestive of benign prostatic hyperplasia: a prospective study

OBJECTIVES

To investigate the benefit of alpha1-adrenoceptor antagonist naftopidil on the quality of life (QOL) of patients with lower urinary tract symptoms suggestive of benign prostatic hyperplasia (BPH/LUTS).

METHODS

A total of 99 men with BPH/LUTS were prospectively recruited. The Short Form-8 (SF-8) was used for generic QOL assessment and each parameter was compared with the norm in these patients. Longitudinal changes were evaluated using the SF-8 and the International Prostatic Symptoms Score (I-PSS) at baseline, 4 and 8 weeks after naftopidil administration. The relationship between SF-8 and I-PSS was analyzed.

RESULTS

Five of eight components in the SF-8 were significantly lower than the Japanese national norm at baseline. SF-8 score was improved by naftopidil at 4 and 8 weeks in general health (GH) and physical component summary (PCS) in the patients in their 70s. Mental health (MH) and mental component summary (MCS) were improved at 8 weeks in patients in their 60s. When analyzing the whole cohort, SF-8 GH, role emotional (RE) and MH had improved at 8 weeks, which was similar to the norm, and bodily pain (BP) results were better. Compared with the baseline, total I-PSS, storage/voiding symptoms and QOL index scores improved significantly under naftopidil. Each component of I-PSS (except for hesitancy) correlated with SF-8 sub-scales (except for BP) to some extent.

CONCLUSIONS

BPH/LUTS impairs generic QOL, which is improved by naftopidil treatment. SF-8 can be a useful instrument to assess the efficacy of BPH/LUTS treatment because its simplicity to complete and analyze, and its meaningful relationship to I-PSS.

Benign prostatic hyperplasia: symptoms, symptom scores, and outcome measures

The approach to a patient with benign prostatic hyperplasia and lower urinary tract symptoms (LUTS) begins with a detailed history. The goal is to clearly identify the patient's urinary complaints, including frequency of micturition, urgency, urge incontinence, weak stream, the need to push or strain, hesitancy, intermittency, dysuria, and hematuria. Bladder diaries and symptom questionnaires are useful as adjuncts to information that is acquired in the history. The voiding diary is an essential part of the workup. The voiding diary differs from a simple frequency-volume chart in that it incorporates not only the frequency, voided volume, urge episodes, pad usage, and fluid intake but also the data related to patient activities. It allows patients to have a more thorough self-evaluation of their LUTS.

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

BACKGROUND

Benign prostatic hyperplasia (BPH) is a common condition in aging men causing lower urinary tract symptoms (LUTS). Treatment aims are to relieve symptoms and prevent disease progression. Of the different alpha-1 adrenergic receptors (ARs) in the prostate, alpha-1a receptors are known to be central to prostatic smooth-muscle contraction. Recent studies have shown that patients with BPH may also have a predominance of alpha-1d receptors.

OBJECTIVES

To evaluate the efficacy and adverse effects of naftopidil, a selective alpha-1d oral alpha-blocking agent for the treatment of LUTS associated with BPH.

SEARCH STRATEGY

Systematic review of trials published January 1950 to January 2009. Sources included MEDLINE and bibliographies of retrieved articles and review articles.

SELECTION CRITERIA

Eligible trials included: men diagnosed with symptomatic BPH; compared Naftopidil to placebo, control, or combination therapy; evaluated clinically relevant outcomes between randomized groups; had at least 4-weeks follow up; and were published in English language.

DATA COLLECTION AND ANALYSIS

Participant demographics and comorbidities, enrollment criteria, outcomes, adverse events, numbers and reasons for dropouts were extracted onto standardized extraction forms by one reviewer. The mean change and per cent improvement from baseline in AUA (American Urological Association Symptom Score) and IPSS (International Prostate Symptom Score) scores and other efficacy outcomes for treatment and control groups were calculated. If feasible, the efficacy outcomes and adverse events data were pooled.

MAIN RESULTS

Eight trials were eligible (N = 744 participants). All trials were conducted in Japan. Study duration ranged from 4 to 17 weeks. The mean age of participants was 68 years; pretreatment mean IPSS = 17.8 and mean peak urine flow (Qmax) = 9.5 mL/s (milliliters/second). No trials compared naftopidil to placebo. In 5 trials (N = 419), naftopidil in doses of 25 to 75 mg/d (milligrams/day) showed a mean IPSS improvement similar to low-dose tamsulosin (0.2 mg/d) (8.4 versus 8.9 points). Compared to a phytotherapy preparation (eviprostat), naftopidil significantly improved total IPSS (-5.9 versus 0.4; P < 0.0002). In one trial, the addition of anticholinergic drugs (oxybutynin or propiverine hydrochloride) to naftopidil did not offer any significant improvement for IPSS or Qmax in comparison to treatment with naftopidil alone. Although IPSS did not significantly differ between high- (75 mg/d) and low-dose (25mg/d) naftopidil, high dose significantly improved Qmax compared to low dose (1.2 mL/s versus 0.2 mL/s). Adverse events reported were few, mild and similar to those seen with 0.2 mg/d tamsulosin.

AUTHORS' CONCLUSIONS

There are no data from placebo controlled trials regarding the efficacy of naftopidil in men with symptomatic BPH. Limited information suggests that treatment with naftopidil provides short-term improvement in urinary symptom-scale scores (total IPSS/AUA), QoL (quality of life) score, and urinary symptoms from baseline comparable to low-dose tamsulosin. Adverse effects due to naftopidil were few and usually mild.

Alpha 1-adrenoceptor pharmacome: alpha 1L-adrenoceptor and alpha 1A-adrenoceptor in the lower urinary tract

Alpha(1)-adrenoceptors are involved in physiological functions such as urinary excretion and ejaculation in the lower urinary tract (LUT). Several alpha(1) antagonists are clinically used for the treatment of urinary obstruction in patients with benign prostatic hyperplasia. At present, three classical alpha(1)-adrenoceptor subtypes (alpha(1A), alpha(1B), and alpha(1D)) have been identified, among which the alpha(1A) and alpha(1D)-adrenoceptor subtypes have been regarded as the main targets of alpha(1) antagonist therapy for LUT symptoms. Prazosin has been used as a prototypic, classical antagonist, to characterize alpha(1)-adrenoceptors pharmacologically, (i.e. all classical alpha(1)-adrenoceptor subtypes show high-affinity for the drug). However, we found that alpha(1)-adrenoceptors in the LUT show atypical low-affinity for prazosin. Therefore, the concept alpha(1L)-receptor, which indicates alpha(1)-adrenoceptor(s) showing low-affinity for prazosin has been introduced. A recent study demonstrated that the alpha(1L)-adrenoceptor is a specific phenotype present in the many intact tissues including human LUT, and that it originates from the ADRA1A gene. Therefore, the alpha(1L)-adrenoceptor in the LUT is now re-defined as alpha(1A(L))-adrenoceptor. The physiological and pharmacological difference between classical alpha(1A(H),) and alpha(1A(L)) which is the native receptor expressed in the LUT is of special interest as it provides fundamental bases for urological alpha(1A)-adrenoceptor blocking pharmacotherapy. Here, we briefly review the alpha(1)-adrenoceptors in the LUT with special reference to phenotype-based (pharmacome) analysis.