Flashcards in antihistamine-OTC meds Deck (48)
Where are histamines Stored?
They are stored in the forms of granules in the mast cells (tissues) or basophils (blood)
How are these histamines released?
1. Immunologic release- IgE mediated, causes degranulate on exposure to antigen (Type I response)
2. Amine Drugs- can displace histamine from storage (morphine, codeine, vancomycin)
What receptors do histamines act on?
H1, H2, and H3
What is histamines effect on cardiovascular H1 receptors? how bout H2 receptors?
1. Vasodilation of arterioles-hypotension, nasal congestion
2. Increased capillary permeability (hypovolemic shock, edema, urticaria/ hives)
Effect on H2 is direct cardiac stimulation and vasodilation
What will be the effect of histamines on the GI-tract?
1. Contraction of smooth muscle (H1)
2. increased gastric acid secretion (H2)
When someone is having a bad allergic reaction there throat closes up. What effect do you think histamines have on bronchiolar smooth muscle?
Opens them SIKE.... its bronchoconstriction
What are the 4 major classes of antihistamines? (H1 receptor antagonists)
1. H1 receptor blockade
2. Muscarinic receptor blockade
3. sodium channel blockade
4. adrenergic receptor blockade
true or fals 1st gen antihistamines have additional blocking actions at non-H1 receptors?
What is one benefit of 2nd gen antihistamines compared to 1st gen when talking about H1 receptor blockade
2nd gen are highly specific for H1 receptors
Do both 1st gen and 2nd gen histamines have equal efficacy in blocking H1 receptors?
Antihistamines have also work by a muscarinic receptor block. Out of the two 1st gen and 2nd gen which ones cause less sedation
2nd gen- they also have less complete CNS penetration
Anithistamines can act as an alpha 1 receptor block. What can this result in and what antihistamine causes this?
Can results in orthostatic hypotension
What generation of antihistamine is best for allergic rhinitis?
2nd-gen: not really sure why- maybe because its selectivity for H1 receptor is more specific
What can 1st gen antihistamines treat that 2nd gen can not.
1st gen antihistamines can be used for
1. cough supression- Na channel block
2. Motion sickness- H1 and M receptor block
3. Nausea and vomiting- H1 and M receptor block
4. Sleep aid for insomnia- H1 and M receptor block
Antihistamines are great for treating allergic rhinitis. But what it the best?
Which gen of antihistamines has CNS penetration?
1st gen- resulting in more theraputic actions
helps with insomnia, motion sickness
How are antihistamines metabolized?
hepatic metabolism by CYP3A4
What are some the of the time frames for 1st gens to be metabolized
What are some the of the time frames for 2nd gen antihistamines to be metabolized
12hrs for fexofenadine
24 hrs for loratadine
which gen has a greater chance of causing a sedation side effect
1st gen (benadryl)
Which generation antihistamine 1st or 2nd produces an antimuscarininc action causing dry mouth?
Which generation antihistamine 1st or 2nd produces a paradoxical excitation
Which generation antihistamine 1st or 2nd produces a postural hypotensive effect?
1 st gen has an alpha 1 blocker effect (promethazine)
What are the first gen antihistamines
Which 1st gen has the lowest sedative effect?
Which 1st gen has the highest antiemetic effect?
which 1st gen antihistamine has a medium anticholinergic effect?
yep C meclizine again
Both A and B have the exact same effects on sedation, antiemetic, and anticholinergic
Can second gen antihistamine cross BBB and do they have any anticholinergic effects?
no they can not cross the BBB and they do not have any anticholinergic effects
what are the 2nd gen antihistamine meds?