OTC Sleep Aids Containing Antihistamines Can Exacerbate Urinary Retention
Over-the-counter sleep aids containing antihistamines like diphenhydramine can significantly worsen urinary retention due to their anticholinergic properties, and should be avoided in patients with existing urinary difficulties or risk factors for retention.
Mechanism of Urinary Retention with Antihistamine Sleep Aids
- Diphenhydramine, a common ingredient in OTC sleep aids, has significant anticholinergic properties that can impair bladder contraction and contribute to urinary retention 1
- The FDA drug label for diphenhydramine explicitly warns patients to consult a doctor before use if they have "trouble urinating due to enlarged prostate gland" 2
- Antihistamines with anticholinergic effects are among the medication classes most frequently associated with drug-induced urinary retention 3
Risk Factors for Antihistamine-Induced Urinary Retention
- Elderly patients are at significantly higher risk for developing urinary retention from antihistamines due to:
- Age-related changes in bladder function
- Higher prevalence of comorbidities like benign prostatic hyperplasia
- Concurrent use of other medications that may compound anticholinergic effects 3
- Male patients, particularly those with prostatic enlargement, face greater risk of retention when using antihistamine sleep aids 4
- Patients already taking other medications with anticholinergic properties may experience additive effects when adding diphenhydramine 3, 5
Evidence of Urinary Retention with Antihistamines
- Urinary retention is specifically listed as an adverse effect of diphenhydramine in multiple clinical guidelines 1
- Case reports document acute urinary retention triggered by antihistamines like dimenhydrinate, particularly when combined with other medications affecting urination 6
- Studies show that up to 10% of urinary retention episodes may be attributable to medication effects, with anticholinergic drugs being major contributors 3
Prevalence of Inappropriate Use
- A study of older adults found that 59% of those using OTC sleep medications were taking products containing diphenhydramine or doxylamine, despite these being classified as potentially inappropriate for older adults 7
- Many patients taking these medications were unaware of the safety risks, with only 38% of users recognizing potential dangers 7
Alternative Approaches for Sleep
- The American Academy of Sleep Medicine recommends cognitive-behavioral therapy for insomnia (CBT-I) as first-line treatment for chronic insomnia before considering medication 8
- When pharmacological treatment is necessary, non-benzodiazepine receptor agonists (like zolpidem) prescribed at appropriate doses may be preferable to OTC antihistamines for patients without contraindications 8
- For patients with urinary concerns who require medication for sleep:
- Consult with a healthcare provider for appropriate alternatives
- Consider medications with fewer anticholinergic effects
- Use the lowest effective dose for the shortest duration possible 8
Management of Antihistamine-Induced Urinary Retention
- If urinary retention develops after taking an antihistamine sleep aid:
- Patients with a history of urinary symptoms should be counseled to avoid OTC sleep aids containing antihistamines 2, 3
Clinical Recommendations
- Screen patients for urinary symptoms or risk factors before recommending OTC sleep aids
- Educate patients about the anticholinergic effects of diphenhydramine and similar antihistamines
- Consider non-pharmacological approaches to sleep improvement as first-line interventions 8
- For patients requiring pharmacological intervention, consult with a healthcare provider about prescription alternatives with more favorable urinary side effect profiles 8