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CLINICAL PRACTICE |
Address correspondence to David O. Sussman, DO, Urology Associates, PA, 205 E Laurel Rd, Stratford, NJ 08084-1301. E-mail: dosuss{at}comcast.net
Overactive bladder is a highly prevalent condition, affecting approximately 33 million adults in the United States. Despite the considerable impact this condition has on patients' quality of life, overactive bladder remains underrecognized and undertreated as a result of patient embarrassment and reluctance to seek medical help, as well as a lack of proactive questioning by physicians. The present article encourages physicians to initiate a dialogue with patients regarding urinary control and, specifically, overactive bladder. Treatment options for overactive bladder recommended in the current article include both nonpharmacologic and pharmacologic therapies. Properties of antimuscarinic agents, including three new drug therapies, are reviewed and provided for physicians to optimize therapy options, particularly among elderly patients.
The International Continence Society (ICS) defines overactive bladder as urgency (with or without urge incontinence), usually with frequency and nocturia, in the absence of other pathologic or metabolic conditions that might explain the symptoms.3 Urgency is defined as a sudden and compelling desire to pass urine that is difficult to defer. Nocturia is defined as waking one or more times per night to void urine. The ICS definition of overactive bladder describes the condition using patient symptoms rather than urodynamic findings. This is an important distinction, as urodynamically detectable detrusor overactivity may not be present in up to 25% of patients with overactive bladder.4
Patient quality of life (QOL) is substantially impacted by this disorder as social, psychological, occupational, domestic, physical, and sexual functioning are all affected.5 As a consequence, severe bladder symptoms can have a tremendous negative impact on patient social interaction, sexual intimacy, and even willingness to leave home. In addition, while most people recognize that incontinence, frequency, and nocturia affect patients' QOL, a 2004 survey6 suggests that urinary urgency alone also has a significant impact on QOL.
In fact, the impact of this disorder extends beyond basic QOL issues and into financial implications and patient comorbidities. In 2000, for example, the total costs associated with overactive bladder in the United States were estimated at $12 billion.7 These expenses comprise indirect costs (eg, lost productivity) and direct costs, including diagnosis, treatment, and routine care. Comorbidities associated with this condition include skin infections, urinary tract infections, depression, and, in older adults, injuries associated with falls that occur as a result of hurrying to the toilet.
The past 10 years have seen many developments related to overactive bladder, both in terms of physicians' greater understanding of the implications of this condition and the treatment options available. In 2003 and 2004, the US Food and Drug Administration (FDA) approved three new agents—darifenacin, solifenacin succinate, and trospium chloride—for the treatment of patients with overactive bladder. Some of these agents differ substantially from earlier compounds and may allow for optimization of therapy, particularly among older patients. The present article provides an overview of the pathophysiology of overactive bladder and reviews the current diagnostic approaches as well as treatment strategies.
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Pathophysiology |
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 Top Pathophysiology Recognition and DiagnosisTreatment StrategiesConclusionsReferences |
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As bladder volume increases, involuntary contractions of the detrusor muscle are often associated with overactive bladder—though such urodynamically demonstrable detrusor overactivity is not a prerequisite for a diagnosis of the condition. The mechanisms underlying these involuntary contractions have not yet been fully elucidated, although increasing attention is being focused on the role of sensory afferent nerves in the process.8
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Recognition and Diagnosis |
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TopPathophysiologyRecognition and DiagnosisTreatment StrategiesConclusionsReferences |
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To manage overactive bladder effectively, physicians must first encourage patients to speak openly with them. Given the prevalence of this condition, annual physical examinations or medical check-ups may be a good opportunity to discuss urinary problems with patients. A simple question such as "Are you bothered or worried by your urine control?" may be sufficient to initiate discussion. If a patient is concerned about his or her urine control, the physician should ask the patient to fill out a diary detailing the time, estimated volume of urine voided, and experience of each urination (ie, whether or not the urination was associated with urgency). Such a diary can be useful at the diagnosis stage to establish the extent and severity of any urinary problems.
Achieving a differential diagnosis is a relatively straight-forward process that can be performed in the physician's office using a simple diagnostic algorithm for overactive bladder (Figure 1). For patients presenting with one or more symptoms of this condition (frequency, urgency, urge incontinence, or nocturia), a patient history should be obtained—including information about past genitourinary disorders—to exclude symptoms resulting from comorbid conditions or concomitant medications.
A physical examination of the abdomen, rectum, pelvis, and genitalia should be performed to exclude obvious pathologies such as inflammation, prolapse, or masses. Urinalysis should be performed to exclude conditions that are sometimes associated with overactive bladder (eg, bacteria in the urine would suggest an infection, excess glucose in the urine could be a result of diabetes, and blood or protein in the urine may indicate kidney disease). In instances where urinalysis results suggest an associated condition, it may be necessary to refer the patient for additional diagnostic testing. For example, if a patient has unexplained hematuria, a urology referral for cytoscopy is recommended. In the absence of infection or other pathologies, including bladder cancers, a diagnosis of overactive bladder can be made.
Urodynamic assessment can also be used in the diagnosis of overactive bladder, though the value of such assessments for this purpose is controversial. A recent report4 suggests that a positive urodynamic assessment for incontinence does not influence treatment success, indicating that these expensive, invasive, and complex tests should be reserved for patients with unusual symptoms or when initial therapy is unsuccessful.4
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Treatment Strategies |
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TopPathophysiologyRecognition and DiagnosisTreatment StrategiesConclusionsReferences |
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Nonpharmacologic Treatment
Nonpharmacologic interventions in the treatment of patients with overactive
bladder usually involve "bladder retraining," which generally
consists of patient education, scheduled voiding, and urge-suppression
techniques. Educating patients about bladder function is important in detering
patients from using harmful coping behaviors, such as restricting fluid
intake. Patients should also be alerted that consuming certain products (eg,
alcohol, caffeine, spicy foods, and tomato-based products) may exacerbate
their condition. In addition, scheduled voiding can help patients correct the
habit of frequent urination and increase bladder capacity. Finally, urge
suppression techniques such as pelvic floor muscle exercises (Kegel
exercises), which involve tightening and relaxing the muscle around the
rectum, and biofeedback-assisted training can strengthen and improve voluntary
control of muscles.
Within the primary care setting, bladder retraining can be labor-intensive and time-consuming for both the patient and the physician, and successful implementation requires considerable motivation and commitment on the part of the patient. Despite these obstacles, bladder retraining should always be considered in the management of overactive bladder, as it is a safe treatment option from which many patients can benefit.11 Moreover, behavioral modifications that occur as a result of bladder retraining may enhance the outcomes obtained with pharmacologic interventions.9
Pharmacologic Treatment
While a range of drugs have been used in the past for the management of
overactive bladder—from smooth muscle relaxants to tricyclic
antidepressants—antimuscarinic agents now form the mainstay in the
armamentarium used to control the symptoms associated with this condition.
Conventional
wisdom12 holds that
antimuscarinics act by blocking the muscarinic receptors on the detrusor
muscle (which are normally stimulated by acetylcholine released from
parasympathetic nerves) thereby diminishing the intensity of involuntary
detrusor muscle contractions. Emerging
research,12
however, suggests that anti-muscarinic agents mainly act during the storage
phase, decreasing urge and increasing bladder capacity, during which time
there is normally no activity in the parasympathetic nerves.
Studies12-14
are now focusing on the ability of antimuscarinics to modulate afferent
impulses as a means of effectiveness.
Antimuscarinic agents differ at the structural and molecular level, resulting in different metabolism, absorption, potency, and selectivity profiles, as follows:
An understanding of these differences—particularly in how they impact the efficacy and safety of the agents—is important and allows physicians to make informed decisions about the most suitable treatment option for their patients' needs.15-20 A summary of these features is provided in Figure 2.
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Oxybutynin has been available for the treatment of overactive bladder for more than 30 years and is effective in a range of patients. It is available as immediate- and extended-release oral tablets (oxybutynin chloride) and as a transdermal patch.30,35 The most commonly reported adverse event for extended-release oral oxybutynin is dry mouth, experienced by up to 68% of patients and causing some patients to discontinue therapy.36 Transdermal oxybutynin results in a far lower incidence of dry mouth (<10%) but is associated with local skin reactions such as pruritis.30 This lower incidence of dry mouth is believed to result from the lack of presystemic metabolism to form an active metabolite with similar properties to the parent compound (N-desethyl-oxybutynin).
Certain attributes of oral oxybutynin, such as its relatively small size, highly lipophilic nature, and its neutral charge, make it more likely to cross the blood-brain barrier than other antimuscarinic agents available for the treatment of overactive bladder. Therefore, central anticholinergic effects, which could result in cognitive impairment, are a concern in patients (particularly elderly patients) taking oxybutynin.37
Tolterodine, which is orally administered, has been available in the United States since 1998. Originally launched as an immediate-release formulation, tolterodine is now available as an extended-release formulation. Initiated and maintained at a dose of 4 mg once daily, tolterodine extended-release formulation is efficacious in the treatment of overactive bladder.38 Tolterodine has comparable efficacy to oxybutynin, but with a reduced incidence of adverse events (eg, dry mouth).37,39,40 Although preliminary reports41,42 have drawn an association between tolterodine and impaired cognitive functioning, tolterodine is less lipophilic than oxybutynin and is therefore less likely to cross the blood-brain barrier.43
Newer oral antimuscarinic agents darifenacin (7.5 mg and 15 mg) and solifenacin (5 mg and 10 mg) were approved for the treatment of overactive bladder and urge incontinence by the FDA in 2003 and 2004, respectively. Both agents are well-tolerated and substantially reduce urge incontinence episodes, frequency, and urgency, and increase the volume of urine voided.44-47 The most commonly reported adverse events for both darifenacin and solifenacin are dry mouth and constipation. Darifenacin has little affinity for the M1 muscarinic subtype receptor, a feature that is proposed to minimize cognitive effects that might arise if the compound were to cross the blood-brain barrier. Accordingly, adverse cognitive effects have not been reported for darifenacin.48 Solifenacin is a nonselective muscarinic antagonist that binds to the M1, M2, and M3 muscarinic receptors—though with slightly greater affinity for M1 and M3 receptors than M2 receptors.49 Animal studies27,49 suggest that solifenacin has the highest degree of bladder selectivity compared with oxybutynin, tolterodine, and darifenacin. In a recent head-to-head trial,50 a flexible dosing regimen with solifenacin was found to be superior to extended-release tolterodine for the majority of efficacy variables investigated. However, because this trial50 was designed to show non-inferiority, these results should be viewed with caution.
Trospium, an antimuscarinic agent approved by the FDA in 2004 for the treatment of overactive bladder, has been available in Europe for more than 20 years. The safety and efficacy of trospium have been demonstrated in clinical trials involving over 3000 patients in the United States and Europe and have been further demonstrated with postmarketing studies involving over 10,000 patients.13 Trospium is unique among the new antimuscarinic agents for several reasons: it has the least selectivity and the highest overall affinity for the muscarinic receptor subtypes; it is a positively charged quaternary amine, which prevents transfer across the blood-brain barrier; and it is minimally metabolized by cytochrome P-450 enzymes, with approximately 60% of the absorbed dose being excreted in the urine in active form. In addition, this agent demonstrates a rapid onset of effect, reducing frequency and urge incontinence within the first few days of treatment.15,34
Trospium also has comparable efficacy to oral oxybutynin and tolterodine, but with fewer adverse events.51 The lack of cognitive adverse effects may result from the inability of trospium to transfer across the blood-brain barrier. The lack of adverse drug-drug interactions is a result of the lack of metabolism by cytochrome P-450 enzymes. Evidence supporting the possible additional benefits of a compound that is active in the urine was provided by a recent study14 in which urine from individuals who had ingested a variety of antimuscarinic agents was injected into the bladders of rats. The results of the study14 showed that, in accordance with its activity in urine, trospium has a local inhibitory effect on detrusor overactivity.
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Conclusions |
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TopPathophysiologyRecognition and DiagnosisTreatment StrategiesConclusionsReferences |
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Nonpharmacologic treatment options, alone or in combination with drug therapy, are effective in treating patients with overactive bladder. The development of new antimuscarinic agents and new formulations of more traditional agents widens the options available for the treatment of this disorder. The differences in efficacy and tolerability profiles among available agents provide the opportunity for physicians to choose the form of therapy that best suits the needs of the individual patient. When treating elderly patients, for example, consideration should be given to the use of agents with low potential to cause cognitive adverse events, and low potential for interaction with concomitant medications.
Submitted June 20, 2006; revision received October 31, 2006; accepted November 2, 2006.
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References |
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| HOME | HELP | FEEDBACK | SUBSCRIPTIONS | ARCHIVE | SEARCH | TABLE OF CONTENTS |
