Voiding Dysfunction Medication

Updated: Oct 29, 2019
  • Author: Christopher S Cooper, MD, FACS, FAAP; Chief Editor: Marc Cendron, MD  more...
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Medication

Medication Summary

Pharmacologic therapy for voiding dysfunction in children usually centers on treating OAB (uninhibited detrusor contractions) during filling and, at times, decreasing bladder outflow resistance. Most of the neurohumoral stimulus for bladder contraction is the stimulation of muscarinic-cholinergic receptor sites on bladder smooth muscle. Anticholinergic agents can depress uninhibited bladder contractions, making this class of medications the mainstay of pharmacologic management of overactive bladder.

However, the effects of anticholinergic drugs on normal contractions, with subsequent incomplete bladder emptying and retention, must also be considered. In addition, certain anticholinergic medications may exacerbate constipation, as they affect the intestinal musculature. In rare instances, bladder outlet resistance is increased because of stimulation of alpha1-adrenergic receptors in the bladder neck; this effect may be decreased by the use of alpha1-adrenoreceptor blockers.

Despite the prevalence and significance of pediatric daytime incontinence, few prospective, randomized trials assessing treatments have been published. This problem was documented by a 2003 review of studies of pediatric incontinence that found only 1 randomized, controlled study that evaluated currently used treatment; that study reported no benefit in the combination of biofeedback and the anticholinergic drug oxybutynin. [43]

Oxybutynin is approved by the US Food and Drug Administration (FDA) for the treatment of OAB in children and has traditionally been the treatment of choice.

In an attempt to define predictive factors that affect the continence outcome in children with daytime wetting, a study evaluated 81 children treated with oxybutynin for an average of 1.2 years. At the last visit while taking oxybutynin, 38% of patients were dry, 31% of patients were significantly improved, 24% of patients were slightly improved, and 7% of patients were unchanged in their symptoms. [44] The only variable significantly associated with improvement in daytime wetting with oxybutynin was the frequency of wetting episodes; those who presented with fewer wetting episodes were more likely to become dry.

One study reviewed 27 children who were changed from immediate-release oxybutynin to the extended-release form. [45] All patients had persistent incontinence while taking regular oxybutynin. By the first visit after changing to the extended-release formulation, however, 48% of the children had become dry or had experienced significant improvement in the frequency of wetting. Voided volume and bladder capacity were also improved.

In addition, fewer adverse effects have been reported for extended-release oxybutynin than for the immediate-release agent. [46]

Oxybutynin is also available in a patch (Oxytrol), as well as a gel (Gelnique). However, neither of these formulations has been approved for use in the pediatric population.

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Antispasmodic Agents, Urinary

Class Summary

These drugs competitively inhibit the binding of acetylcholine to the muscarinic cholinergic receptor, thereby suppressing involuntary bladder contraction of any etiology. In addition, they increase the volume at the first involuntary bladder contraction, decrease the amplitude of the involuntary bladder contraction, and, possibly, increase bladder capacity.

Oxybutynin (Ditropan XL, Gelnique, Oxytrol)

This drug is a synthetic tertiary amine that, like atropine, antagonizes the muscarinic actions of acetylcholine. Oxybutynin has a direct spasmolytic effect on detrusor muscle and small intestine and local anesthetic action. It reduces the incidence of uninhibited detrusor contractions.

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Alpha1-Adrenergic Antagonists

Class Summary

These agents are used to decrease smooth muscle tone in the bladder outlet. A study of doxazosin in dysfunctional voiding associated with urinary retention showed an 88% reduction in residual urine. A placebo-controlled trial, however, did not show an objective benefit. [47]

Alpha-blocker therapy has demonstrated continued benefit in children with primary bladder neck dysfunction after 3 years of treatment. [48]

Doxazosin mesylate (Cardura, Cardura XL)

Doxazosin is a selective inhibitor of alpha1-adrenergic receptors. Blockade of these receptors in the bladder neck decreases outflow resistance.

Terazosin (Hytrin)

Terazosin hydrochloride is a selective inhibitor of alpha1-adrenergic receptors. Blockade of these receptors in the bladder neck decreases outflow resistance.

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Laxatives, Osmotic

Class Summary

These agents are useful when treating constipation and detrusor instability.

Polyethylene glycol-3350 powder for PO solution (MiraLAX, GlycoLax, Glavilax, HealthyLax)

Polyethylene glycol solution is an osmotic agent that causes water to be retained in stool. Despite a lack of specific recommendations, it is widely given to children with voiding dysfunction by primary care physicians, pediatric gastroenterologists, and pediatric nephrologists. The agent is recommended for occasional constipation in adults.

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