Second Generation Antihistamines

Antihistamines commonly used medications for the treatment of allergic reactions. Second generation antihistamines do not cross the blood brain barrier, which limits the sedative effects of the medications.   Antihistamines block histamine receptors, which reduces the effects of histamine in tissues.  Dry mouth is a common side effect of these medications.

Class Drugs

• Cetirizine

• Desloratadine

• Fexofenadine

• Levocetirizine

• Loratadine

Class Mechanism of Action

Blocks histamine receptors but does not cross BBB (blood brain barrier) reducing sedative effects

Histamine receptor blockade results in:

• Decreased nasal and bronchial secretions

• Relaxation of bronchioles

• Relaxes intestinal smooth muscle decreases diarrhea and cramping

• Decreased pruritus

• Increases peripheral resistance in blood vessels

• Decreases heart rate

• Vasoconstriction of capillaries, reducing fluid leakage

• Decreases gastric acid secretions

Class Applications

Allergies

Class Adverse Effects

Sedation much less than 1st generation

Dry mouth

Drug Table

Drug Name	Application	Comments	Image
Cetirizine			"Set" "Ear" "Rind"
Desloratadine			"Dez" "Lorax" "Dining"
Fexofenadine			"Fedex" "Fence" "Dining"
Levocetirizine			"Level" "Set" "Rind"
Loratadine			"Lorax" "Dining"