From the Guidelines
Hydroxyzine and oxybutynin should be used with extreme caution when taken together, especially in elderly patients, and separating doses may not eliminate the risks. Both medications have anticholinergic properties that can cause additive side effects including confusion, dry mouth, blurred vision, constipation, urinary retention, and increased risk of falls 1. Elderly patients are particularly vulnerable to these effects due to age-related changes in metabolism and increased sensitivity to anticholinergic drugs. The use of first-generation antihistamines like hydroxyzine in older adults should be approached with caution due to their potential for adverse effects, including sedation, performance impairment, and anticholinergic effects 1.
If both medications are deemed necessary, healthcare providers should consider using the lowest effective doses, monitoring closely for side effects, and potentially adjusting the timing of doses to minimize peak concentration overlap. However, even with separated doses, the long half-life of hydroxyzine (approximately 20 hours) means significant drug levels remain in the system, potentially continuing to interact with oxybutynin. Alternative medications with fewer anticholinergic properties should be considered when possible for elderly patients. Any patient experiencing increased confusion, severe dry mouth, vision changes, or difficulty urinating should seek medical attention promptly.
Some key considerations for managing polypharmacy in older patients include:
- Deprescribing strongly anticholinergic medications like hydroxyzine and oxybutynin when possible 1
- Using alternative medications with fewer anticholinergic properties
- Monitoring closely for side effects and adjusting doses as needed
- Considering the potential for additive side effects when combining multiple medications with anticholinergic properties 1
From the Research
Drug Interactions and Precautions
- There are no direct studies on the interaction between hydroxyzine and oxybutynin in the provided evidence.
- However, it is known that both drugs can have anticholinergic effects, which may increase the risk of adverse events such as dry mouth, constipation, and dizziness when used together 2.
- In elderly patients, the use of multiple anticholinergic drugs can increase the risk of cognitive impairment, sleep disturbances, and other adverse events 2.
Use in Elderly Patients
- The study by 2 suggests that oxybutynin can be used in elderly patients, but with caution due to the potential for anticholinergic adverse events.
- The study by 3 compared the efficacy and safety of tolterodine and oxybutynin in patients with overactive bladder and found that tolterodine was better tolerated than oxybutynin, with fewer adverse events.
- The study by 4 found that oxybutynin transdermal system improved the quality of life in adults with overactive bladder, but did not specifically address the use of oxybutynin in elderly patients.
Dosing and Administration
- There is no specific guidance on the dosing and administration of hydroxyzine and oxybutynin when used together in the provided evidence.
- However, it is generally recommended to use the lowest effective dose and to monitor patients closely for adverse events when using multiple medications with anticholinergic effects 2.