From the Guidelines
Neither doxylamine succinate nor diphenhydramine HCl is consistently proven to be more effective than the other for treating insomnia or allergies, as they work similarly as first-generation antihistamines. Both medications block histamine H1 receptors and cross the blood-brain barrier, causing sedation. For sleep, both are typically effective for short-term use, with doxylamine succinate (25mg) and diphenhydramine HCl (25-50mg) taken 30 minutes before bedtime. Doxylamine may have a slightly longer duration of action (6-8 hours versus 4-6 hours for diphenhydramine), which could be beneficial for maintaining sleep but might cause more morning grogginess. For allergies, diphenhydramine is more commonly used.
Some key points to consider when choosing between these medications include:
- Individual responses vary significantly, so if one medication doesn't work well or causes unpleasant side effects, trying the other may be worthwhile.
- Both medications can cause dry mouth, blurred vision, constipation, and daytime drowsiness, and neither should be used long-term due to tolerance development and potential cognitive effects, especially in older adults.
- The American Academy of Sleep Medicine clinical practice guideline 1 does not recommend either medication for treating sleep onset or sleep maintenance insomnia, citing limited evidence and potential harms.
- The American College of Physicians clinical practice guideline 1 suggests that clinicians use a shared decision-making approach when considering pharmacological therapy for chronic insomnia disorder, and notes that evidence is insufficient to evaluate the balance of benefits and harms of long-term use of pharmacologic treatments.
Overall, the choice between doxylamine succinate and diphenhydramine HCl should be based on individual patient needs and preferences, and should be made in consultation with a healthcare provider.
From the Research
Comparison of Doxylamine Succinate and Diphenhydramine HCl
- The effectiveness of doxylamine succinate and diphenhydramine HCl can be evaluated based on their use in treating insomnia and allergic reactions.
- A study published in 2020 2 suggests that doxylamine may be appropriate for treating insomnia in the last third of the night, but it does not provide a direct comparison with diphenhydramine HCl.
- A literature review from 2007 3 compares the efficacy and safety of diphenhydramine with nonsedating antihistamines for acute allergic reactions, but it does not include doxylamine succinate in the comparison.
- A systematic review from 2015 4 investigates the efficacy and safety of over-the-counter agents, including diphenhydramine and doxylamine, for occasional disturbed sleep or transient insomnia, and finds that melatonin has more consistent beneficial effects on sleep measures.
Efficacy and Safety
- The 2015 systematic review 4 suggests that diphenhydramine and doxylamine lack robust clinical evidence supporting their efficacy and safety for improving sleep.
- A study from 2017 5 finds that more than half of older adults taking over-the-counter sleep medications use products containing diphenhydramine or doxylamine, despite these ingredients being classified as potentially inappropriate for older adults.
- A pharmacokinetic and pharmacodynamic study from 1990 6 compares the effects of diphenhydramine in elderly adults, young adults, and children, but it does not include doxylamine succinate in the comparison.
Conclusion is not allowed, and the response should continue with more information
- Another study from 2017 5 highlights the importance of awareness about the safety risks of over-the-counter sleep medications, particularly among older adults.
- The 2007 literature review 3 notes that newer antihistamines, such as loratadine and desloratadine, are potentially safer and cause less sedation than first-generation antihistamines like diphenhydramine.