Antihistamine Flashcards
Physiological antagonist of histamine
epinephrine
Therapeutic use of epinephrine
anaphylactic shock
what is the MOA of cromolyn sodium
blocks histamine release from lung mast cells.
Therapeutic use of cromolyn sodium
Prophylactic aerosol for asthma, hay fever.
First generation antihistamines
diphenhydramine, chlorpheniramine, promethazine, meclizine, doxylamine
Second generation antihistamines
Fexofenadine, Cetirizine
First generation features
Enter CNS, sedation and anti-cholinergic (atropine-like)
More GI problems
Second generation features
Do not enter CNS, not sedative, less muscarinic
Metabolized by CYP 3A4, drug interactions
Pharmacokinetics of antihistamines
oral administration
Distributed widely, CNS differs between generations
Topical intranasal or opthalmic agents
Metabolized by P450s (1st gen) CYP3A4s (2nd gen)
What combination formulations exist
pseudoephedrine, phenylephrine to enhance relief of nasal congestion
Applications specific to 1st gen antihistamines
prophylaxis for motion sickness and vertigo
anti-emetic
insomnia/sedative
best antihistamine for motion sickness
promethazine
Consideration for taking fexofenadine
do not take with fruit juices
Which of the second generation drugs causes more drowsiness
Cetirizine
Therapeutic use of diphenhydramine (4)
allergic rhinitis
dermatologic pain and itching
sleep aid
motion sickness- muscarinic effect
Adverse effects of diphenhydramine (4)
Sedation is prominent
Topical allergic responses
May reduce lactation and enters breast milk
Caution or avoid in narrow angle glaucoma
Therapeutic use of chlorpheniramine (3)
Allergic rhinitis
Dermatologic pain and itching
OTC cold remedies
Adverse effects of chlorpheniramine (2)
sedation, but less than diphenhydramine
Less muscarinic effect- glaucoma, reduced lactation
Therapeutic use of promethazine
similar to other 1st gens, ANTI-EMETIC, sedative
Adverse effects of promethazine
similar to other 1st gens, PHOTOSENSITIVITY
Therapeutic use of meclizine
VERTIGO, preventing motion sickness
Adverse effects of meclizine
less sedating than other 1st gens
Therapeutic use of Doxylamine
Morning sickness in pregnancy
Which prototype 2nd gen antihistamine has more drug interactions
Cetirizine, metabolized by CYP3A4
Pharmacokinetics of cetirizine
oral prep, long duration