Antihistamines Flashcards
What are the two 1st generation antihistamines?
Diphenhydramine
Chlorpheniramine
How do the 1st generation antihistamines work?
Reversibly block H1-receptor sites…blocks action of histamine on the cell
Where do 1st generation antihistamines concentrate in the body?
Lungs
Spleen
Brain
Should pregnant/breast-feeding women be cautious with 1st generation antihistamines?
Yes…can cross the placenta and distributes into breast milk
How are 1st generation antihistamines eliminated?
First pass metabolism in liver
Then kidneys to be excreted
What are some side effects of 1st generation antihistamines?
Sedation
Anticholinergic (dry mouth, nose, throat; dysuria)
Anti-alpha-adrenergic
Which 1st generation antihistamine distributed/metabolized faster (including in GI mucosa)?
Chlorpheniramine
What are the 2nd generation antihistamines?
Fexofenadine
Cetirizine
Loratadine
How do 2nd generation antihistamines work?
Selective histamine H1 receptor antagonist
Which 2nd generation antihistamine(s) distribute to small/large intestines, stomach, pancreas, liver, and kidney?
Fexofenadine
Cetirizine
Which 2nd generation antihistamine(s) distribution is mostly undetermined?
Loratadine
Where do 1st generation antihistamines distribute to that 2nd generation antihistamines don’t?
The brain–big reason why 1st generation are sedating and 2nd generation aren’t
What needs to be taken into consideration when determining 2nd generation antihistamine doses?
Kidney function
What metabolizes 2nd generation antihistamines in the liver?
CYP enzymes
Which 2nd generation antihistamine shouldn’t be used by breast-feeding mothers?
Loratadine
