1. Aschenbrenner, Diane S. MS, APRN, BC


* Fesoterodine is a newly approved extended-release medication taken once daily to treat overactive bladder.


* Adverse effects are attributable to its anticholinergic properties.



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Fesoterodine fumarate (Toviaz) has been approved by the Food and Drug Administration for the treatment of overactive bladder in adults. Chemically similar to tolterodine tartrate extended-release capsules (Detrol LA), the manufacturer's other anticholinergic agent for the condition, the new drug is presumed to work by blocking the muscarinic cholinergic receptors in the bladder, relaxing its smooth muscle tissue. (Fesoterodine differs from tolterodine in that it can be taken once rather than twice daily.) When stimulated, muscarinic cholinergic receptors cause contraction of the bladder's detrusor muscle, and blockage of those receptors prevents the detrusor from contracting in response to slight fullness of the bladder. This allows the bladder to fill more fully, thereby diminishing the urinary frequency and urge incontinence characteristic of the overactive bladder.


As fesoterodine blocks muscarinic cholinergic receptors (the most common type of cholinergic receptor) it can also produce effects at other receptors sites throughout the body, and anticholinergic adverse effects are therefore common (dry mouth and eyes, constipation, urinary retention, blurred vision, sedation, and diminished sweating-the latter of which could be dangerous if the patient is in a hot climate); dry mouth and constipation are most frequent. Nurses should teach their patients how to recognize and treat the adverse effects of fesoterodine.


Fesoterodine is metabolized through two cytochrome P (CYP)-450 isoenzyme pathways, CYP2D6 and CYP3A4, and an interaction can occur when a drug that strongly inhibits CYP3A4 (such as ketoconazole [Nizoral], itraconazole [Sporanox], and clarithromycin [Biaxin]) is taken concurrently, significantly elevating its circulating level. Because that drug interaction is more likely with higher doses of fesoterodine, more than 4 mg daily, those medication combinations should be avoided. Nurses should confirm the dose of fesoterodine taken by patients also taking any of these drugs. The interaction between fesoterodine and drugs that inhibit CYP2D6 hasn't been determined, and there are no recommended dosing adjustments.


U.S. Food and Drug Administration. FDA approves Toviaz, a new drug to treat overactive bladder [press release]. FDA News 2008 Oct 31.; Pfizer Labs. Toviaz (fesoterodine fumarate) extended-release tablets [Prescribing information]. 2008 Nov.