Sedative effects of antihistamines.

Area of Science:

• Pharmacology
• Neuroscience
• Clinical Trials

Background:

• H1 antihistamines are widely used for allergic conditions.
• Some antihistamines cause central nervous system (CNS) side effects like drowsiness.
• Loratadine is a newer, long-acting H1 antihistamine developed to minimize CNS effects.

Purpose of the Study:

• To compare the central nervous system effects of loratadine with a standard antihistamine, diphenhydramine.
• To evaluate the impact of loratadine and diphenhydramine on daytime sleepiness and cognitive performance.

Main Methods:

• A double-blind, placebo-controlled study involving 16 healthy adults.
• Participants received loratadine (10 and 40 mg), diphenhydramine (50 mg TID), or placebo for 2 days each, with washout periods.
• Daytime sleepiness was assessed using the Multiple Sleep Latency Test (MSLT), and cognitive performance was measured using a battery of psychomotor tests.

Main Results:

• Diphenhydramine significantly reduced sleep latency compared to placebo, indicating increased daytime sleepiness.
• Neither dose of loratadine affected sleep latency.
• Diphenhydramine significantly impaired performance on tasks such as digit symbol substitution and symbol copying compared to loratadine.

Conclusions:

• Loratadine (10 and 40 mg) demonstrated no clinically significant CNS activity.
• Diphenhydramine significantly increased daytime sleepiness and disrupted cognitive performance.
• Loratadine represents a safer alternative for patients concerned about antihistamine-induced sedation and cognitive impairment.