Does antihistamine make you sleepy
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The Impact of Antihistamines on Sleepiness
Introduction to Antihistamines and Sleepiness
Antihistamines are commonly used medications for treating allergic reactions. However, a notable side effect of many antihistamines is increased sleepiness. This article explores the relationship between antihistamine use and sleepiness, drawing on findings from multiple research studies.
First-Generation Antihistamines and Daytime Sleepiness
Diphenhydramine and Sleep Latency
Diphenhydramine, a first-generation antihistamine, has been shown to significantly reduce sleep latency, meaning it makes people fall asleep faster during the day. In a study where subjects were given diphenhydramine, terfenadine, or a placebo, those who took diphenhydramine fell asleep significantly faster than those who took terfenadine or the placebo1. Another study confirmed that diphenhydramine increased daytime sleepiness and disrupted performance efficiency, unlike loratadine, a second-generation antihistamine2.
Sedative Effects and Performance Impairment
The sedative effects of diphenhydramine are well-documented. It not only increases sleepiness but also impairs cognitive and motor performance. Subjects who took diphenhydramine showed reduced performance in tasks requiring vigilance and reaction time2. This sedative effect is significant enough that diphenhydramine is sometimes used as a non-prescriptive remedy for insomnia9.
Tolerance Development
Interestingly, tolerance to the sedative effects of diphenhydramine can develop rapidly. In a study where subjects took diphenhydramine for four days, initial sleepiness and performance impairment were significant but returned to baseline levels by the fourth day, indicating that the body can quickly adapt to the sedative effects of this drug7.
Second-Generation Antihistamines and Sleepiness
Terfenadine and Loratadine
Second-generation antihistamines like terfenadine and loratadine are designed to minimize central nervous system effects, including sleepiness. Studies have shown that terfenadine does not significantly affect sleep latency or psychomotor performance compared to a placebo3. Similarly, loratadine did not reduce sleep latency or impair performance in tests, indicating it does not induce significant sleepiness2.
Impact on Sleep Quality
While second-generation antihistamines are less likely to cause daytime sleepiness, they can still affect sleep quality. For instance, patients taking cetirizine and hydroxyzine reported higher levels of daytime sleepiness and fatigue compared to those taking newer antihistamines like desloratadine and rupatadine4. However, these newer antihistamines were associated with improved sleep quality and reduced dream anxiety4.
Residual Sedative Effects
Diphenhydramine and Next-Day Sedation
The residual sedative effects of diphenhydramine can extend into the next day. A study using positron emission tomography (PET) found significant brain H1 receptor occupancy the morning after taking diphenhydramine, indicating prolonged sedative effects5. This suggests that even after a night's sleep, diphenhydramine can still cause daytime drowsiness.
Conclusion
In summary, first-generation antihistamines like diphenhydramine are associated with significant daytime sleepiness and performance impairment, although tolerance can develop quickly. Second-generation antihistamines generally do not cause significant sleepiness, but they can still affect sleep quality. Understanding these effects is crucial for both patients and healthcare providers to make informed decisions about antihistamine use, especially when considering the potential for next-day sedation.
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Most relevant research papers on this topic
Daytime sleepiness and antihistamines.
Diphenhydramine at 150 mg produces sleepiness but shows little potential as a hypnotic, and accumulated sleep across the day makes people more alert.
RCT
Highly CitedSedative effects of antihistamines.
Loratadine does not significantly affect central nervous system activity, while diphenhydramine increases sleepiness and disrupts performance efficiency.
RCTHighly CitedEvaluation of antihistamine‐related daytime sleepiness
Terfenadine does not induce daytime sleepiness as measured by multiple sleep latency test.
RCTAssessment of the effects of antihistamine drugs on mood, sleep quality, sleepiness, and dream anxiety
Both classic and new-generation antihistamines increase daytime sleepiness and nocturnal sleep quality, with classic antihistamines negatively impacting mood.
Non-RCTNext-Day Residual Sedative Effect After Nighttime Administration of an Over-the-Counter Antihistamine Sleep Aid, Diphenhydramine, Measured by Positron Emission Tomography
The next-day residual sedative effect of diphenhydramine, an over-the-counter sleep aid, was confirmed by PET measurement, highlighting the need for caution during their administration.
RCTPathobiology of Second-Generation Antihistamines Related to Sleep in Urticaria Patients
High-dosed second-generation antihistamines improve sleep patterns and quality of life in chronic spontaneous urticaria patients without increasing daytime sleepiness.
Non-RCTTolerance to Daytime Sedative Effects of H1 Antihistamines
Tolerance to the sedative effect of first-generation H1 antihistamines like diphenhydramine develops rapidly, with tolerance complete by the end of 3 days of administration.
RCTHighly CitedA comparison between astemizole and other antihistamines on sleep-wakefulness cycles in dogs
Astemizole has no significant effect on sleep-wakefulness patterns in dogs, suggesting it may lack common side-effects of antihistamines like sedation and dryness of mucosal surfaces.
Non-RCT
Animal StudyFirst generation antihistaminic drugs used in the treatment of insomnia – superstitions and evidence
First-generation antihistamines have few studies on their efficacy in treating sleep disorders, with doxylamine and diphenhydramine only registered for accidental insomnia treatment, and no studies justifying the use of hydroxyzine for insomnia treatment.
Systematic ReviewNew findings in pharmacological effects induced by antihistamines: from PET studies to knock‐out mice
Antihistamines can impair cognitive performance in humans when taken at recommended doses, affecting sleepiness and affecting histamine H1 receptor occupancy in the brain.
Non-RCTAnimal Study