Can medications with anticholinergic properties, such as amitriptyline, be used in the same way as oxybutynin (antimuscarinic) for treating incontinence?

From the Guidelines

No, medications with anticholinergic properties like amitriptyline should not be used in the same way as oxybutynin for treating incontinence. While both drugs have anticholinergic effects, they are designed for different primary purposes. Oxybutynin is specifically approved for treating overactive bladder and urinary incontinence, typically starting at 5 mg two to three times daily, with extended-release formulations available at 5-10 mg once daily 1. Amitriptyline, primarily an antidepressant, is not FDA-approved for incontinence treatment. Although amitriptyline does have anticholinergic effects that might theoretically help with bladder symptoms, its anticholinergic action is less selective for the bladder and comes with more significant side effects including sedation, dry mouth, constipation, and cognitive effects, particularly in older adults.

For incontinence treatment, it's better to use medications specifically designed and tested for this purpose, such as oxybutynin, tolterodine, solifenacin, or mirabegron, which have more targeted effects on bladder function with fewer systemic side effects 1. The American College of Physicians recommends pharmacologic treatment in women with urgency UI if bladder training was unsuccessful, and clinicians should base the choice of pharmacologic agents on tolerability, adverse effect profile, ease of use, and cost of medication 1.

Some key points to consider when choosing a pharmacologic agent for incontinence treatment include:

• The effectiveness of the medication in achieving continence rates and improving UI symptoms
• The risk of adverse effects, such as dry mouth, constipation, and cognitive effects
• The ease of use and cost of the medication
• The patient's individual characteristics, such as age, comorbid conditions, and baseline UI symptoms

Overall, while amitriptyline may have some anticholinergic effects, it is not a suitable substitute for oxybutynin or other medications specifically approved for incontinence treatment due to its less selective anticholinergic action and higher risk of significant side effects 1.

From the FDA Drug Label

Oxybutynin chloride exerts a direct antispasmodic effect on smooth muscle and inhibits the muscarinic action of acetylcholine on smooth muscle. Oxybutynin chloride relaxes bladder smooth muscle In patients with conditions characterized by involuntary bladder contractions, cystometric studies have demonstrated that oxybutynin chloride increases bladder (vesical) capacity, diminishes the frequency of uninhibited contractions of the detrusor muscle, and delays the initial desire to void

Medications with anticholinergic properties, such as amitriptyline, are not explicitly mentioned in the provided drug labels as alternatives to oxybutynin for treating incontinence. The labels discuss the anticholinergic effects of oxybutynin, but do not provide direct information on the use of other anticholinergic medications, like amitriptyline, for this specific purpose.

• The primary action of oxybutynin is as an antimuscarinic agent, which is distinct from the primary use of amitriptyline as an antidepressant, although amitriptyline does have anticholinergic properties.
• No direct comparison or substitution guidance is provided in the labels for using amitriptyline in the same way as oxybutynin for incontinence.
• Given the lack of direct information, it cannot be concluded that amitriptyline can be used in the same way as oxybutynin for treating incontinence based on the provided drug labels 2, 2.

From the Research

Medications with Anticholinergic Properties for Incontinence

Medications with anticholinergic properties, such as amitriptyline, have been used to treat various conditions, including incontinence. However, their use and effectiveness in treating incontinence compared to antimuscarinics like oxybutynin need to be examined.

Comparison with Oxybutynin

Oxybutynin is a well-established antimuscarinic used to treat overactive bladder and incontinence 3, 4, 5. Studies have shown that oxybutynin is effective in reducing the frequency of incontinence episodes, the number of voids per day, and the number and severity of urgency episodes compared to placebo 3, 4. However, oxybutynin can cause anticholinergic side effects, leading to poor tolerability in some patients 3, 4, 5.

Amitriptyline for Incontinence

Amitriptyline, a tricyclic antidepressant with anticholinergic properties, has been used to treat idiopathic fecal incontinence 6. A study found that amitriptyline improved incontinence scores, reduced the number of bowel movements, and decreased the frequency and amplitude of rectal motor complexes in patients with idiopathic fecal incontinence 6. However, its use in treating urinary incontinence is not as well-established as oxybutynin.

Key Differences and Considerations

• Amitriptyline has been used to treat fecal incontinence, while oxybutynin is primarily used to treat urinary incontinence due to overactive bladder.
• The effectiveness of amitriptyline in treating urinary incontinence is not as well-studied as oxybutynin.
• Both medications can cause anticholinergic side effects, but the severity and frequency of these side effects may vary between the two medications.

Efficacy and Safety of Antimuscarinics

A systematic literature review and mixed treatment comparison found that mirabegron, a β3-adrenoceptor agonist, had similar efficacy to antimuscarinics, including oxybutynin, in reducing the frequency of micturition, incontinence, and urgency urinary incontinence episodes 7. However, mirabegron had a lower incidence of dry mouth, a common side effect of antimuscarinics. The review highlights the importance of considering the efficacy and safety profiles of different medications when treating overactive bladder and incontinence.

Some key points to consider:

• Oxybutynin is a well-established treatment for overactive bladder and incontinence, but it can cause anticholinergic side effects.
• Amitriptyline has been used to treat fecal incontinence, but its use in treating urinary incontinence is not as well-established.
• The choice of medication should be based on individual patient factors, including the type and severity of incontinence, medical history, and potential side effects.