What is the role of darifenacin (Enablex) in urinary incontinence treatment?

Updated: Sep 23, 2019
  • Author: Sandip P Vasavada, MD; Chief Editor: Edward David Kim, MD, FACS  more...
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Answer

Another anticholinergic agent is the extended-release product darifenacin (Enablex). It has high affinity for M3 receptors involved in bladder and GI smooth muscle contraction, saliva production, and iris sphincter function. A prospective, randomized, placebo-controlled, double-blind study demonstrated the efficacy of extended-release darifenacin with regard to reductions in incontinence episodes, decreases in frequency and urgency, and improved bladder capacity. [68]

The initial dose is 7.5 mg PO qd. After 2 weeks, the dose may be increased to 15 mg/d based on response. [68] Do not exceed 7.5 mg/d if moderate hepatic impairment (Child-Pugh class B) is present or the patient is also taking potent CYP-450 3A4 inhibitors.

Additive toxicity may occur if administered with other anticholinergics (eg, antihistamines). Coadministration with CYP-2D6 substrates that have a narrow therapeutic index (eg, flecainide, thioridazine, TCAs) may cause toxicity of these other 2D6 substrates. Coadministration may also increase midazolam or digoxin levels.

Increasingly, prolongation of the QT interval has been recognized as a potential problem in antimuscarinic drugs as well as medications of many different classes. Individuals with pharmacologic prolongation of the QT interval may be at increased risk for potentially fatal polymorphic ventricular tachyarrhythmia. Additional risk factors for this problem include female gender, advanced age, hypokalemia, and polypharmacy.

No direct studies compare the incidence of prolonged QT intervals or clinically concerning tachyarrhythmias among commonly prescribed antimuscarinic agents. However, in a study of 188 healthy volunteers receiving therapeutic (15 mg) and supratherapeutic doses of darifenacin, no prolongation of the corrected QT interval could be documented. [69]

More commonly observed adverse effects include xerostomia, constipation, and blurred vision. Darifenacin must be swallowed whole; do not chew, divide, or crush.


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