Sedative Effects of Antihistamine Drugs

Antihistamine medications may be associated with significant sedating effects. This has been reduced with the newer second generation antihistamines.

Drug	Generation of Antihistamine	Sedation with a Regular Dose	Sedation with a High Dose
brompheniramine	first	moderate	high
cetirizine	second	mild	moderate
chlorpheniramine	first	moderate	high
clemastine	first	high	very high
desloratadine	second	none	mild
diphenhydramine	first	high	very high
fexofenadine	second	none	none
loratadine	second	none	mild

The sedating effects may be beneficial if taken before bed.

The sedating effects can also cause significant impairment, especially in critical situations that require fine motor control.

Additional conditions that may contribute to sedation and the potential for impairment:

(1) level of sleep hygiene

(2) comorbid sleep disorders (sleep apnea, insomnia, etc)

(3) concurrent alcohol or sedating drugs

(4) interacting drugs that raise the level of antihistamines or prolong their effect (comparable to taking a higher dose)

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