From the FDA Drug Label
The incidence of dry mouth leading to study discontinuation occurred in 0%, 0.9%, and 0% of patients treated with darifenacin 7.5 mg daily, darifenacin 15 mg daily and placebo, respectively. In the two Phase 3 studies, constipation, dry mouth, and urinary retention led to discontinuation in 1%, 0.7%, and 0.5% of patients treated with trospium chloride extended-release capsules 60 mg daily, respectively.
- Darifenacin had a dry mouth incidence of 0% and 0.9% for 7.5 mg and 15 mg daily doses, respectively 1.
- Trospium had a dry mouth incidence of 10.7% for 60 mg daily dose 2. Based on the provided information, darifenacin 7.5 mg is the urinary antispasmodic that is least likely to cause xerostomia (dry mouth).
From the Research
Trospium chloride is the urinary antispasmodic least likely to cause xerostomia (dry mouth). This medication stands out among anticholinergic agents used for overactive bladder because it has a quaternary amine structure that limits its ability to cross the blood-brain barrier and reduces its penetration into salivary glands 3. While all anticholinergic medications can potentially cause dry mouth to some degree, trospium's chemical properties result in fewer antimuscarinic side effects compared to alternatives like oxybutynin, tolterodine, solifenacin, or darifenacin.
Key Points to Consider
- Trospium is typically prescribed at 20 mg twice daily with the extended-release formulation available as 60 mg once daily 4.
- Patients should take it on an empty stomach, at least one hour before meals, as food can decrease its absorption 3.
- Despite having a lower incidence of dry mouth, patients using trospium should still maintain good oral hygiene, stay hydrated, and report persistent dry mouth symptoms to their healthcare provider, as medication adjustments may be necessary.
- The most recent and highest quality study available supports the use of trospium chloride as an effective and well-tolerated treatment for overactive bladder, with a lower incidence of dry mouth compared to other anticholinergic agents 4.
Comparison with Other Anticholinergic Agents
- Solifenacin and darifenacin are also used to treat overactive bladder, but they may have a higher incidence of dry mouth compared to trospium chloride 5.
- Oxybutynin and tolterodine are other anticholinergic agents used to treat overactive bladder, but they may have a higher incidence of dry mouth and other antimuscarinic side effects compared to trospium chloride 6, 3.