Exam1Lec7Histamines Flashcards
Allergy is also referred to as atopy which is what?
a disorder of the immune system resulting in excessive histamine release.
What are common allergic rxns? Allergic rxns can occur to what?
eczema, hives, hay fever, asthma
food allergens, drug allergens, and to the venom of stinging insects such as wasps and bees
What are the first-gen antihistamine?
Chlorpheniramine
Diphenhydramine
Hydroxyzine
What are the second-gen antihistamine?
Cetirizine
Azelastine (intranasal)
Loratadine
Fexofenadine
What is the main difference between 1st and second generation antihistamines?
1st can cross the blood brain barrrier and cause sedation
2nd does not cross the BBB (not sedative)
What are autocoids and what do they include?
Endog cmpd that are produced by neural and non-neural tissues. Autacoids include monoamines such as histamines and serotonin, prostaglandins as well as leukotrienes.
Histamine can be released is response to what?
Injury or a local hormone (also prostaglandins & leukotrienes) in response to an allergic rxn.
High concentration of histamine may lead to
anaphylactic shock
What do drugs for autocoids do to alleviate allergic rxns?
inhibit the synthesis or block the receptor for autocoids
The drugs that activate autocoid receptors are helpful for what?
Inducing labor, fighting migraines headaches and other purposes
How are histamines made?
Made by Histidine (amino acid) by the enzyme L-Histidine decarboxylase
histamines are stores in granules (vesicles)
Anyibody-antigen complex interacts with GPCR’s where?
Mast cells and basophils (abundant in the GI tract, skin, and RT) resulting in release of histamines
HISTAMINES are metabolized by ____ enzymes within the GI tract and liver
n-methyltransferase
Degranulation of Mast cells
stimuli that incr ____ increases ____.
cGMP, histamine
those incr the cAMP, lower histamine
Histamine is an ____ for GPCR.
agonist
Activation of Histamine receptors result in what?
incr in cGMP on smc and neurons
Activation of what isoform of Histamine receptor are involved in allergic rxns?
H1(gpcr)
causing dermatiis, rhinits, conjuctivitis
Activation of H1 results in what 4 things?
- Vasodilation (resulting in a decr in blood pressure)
- Incr vascular permeability (leads to erythema, congestion, edema, inflammation)
- Nerve ending cause pruritus (itching) and in lugs initiates the cough reflex.
- Bronchoconstriction and contraction of most gastrointestinal smooth muscles
Antihistamines are
antagonist?
inv agonsists?
agonists?
of H1 receptor
inverse agonists
Antihistamines are inverse agonists of mainly H1 type histamine receptors (G protein-coupled receptors).
Antihistamines block production of what?
cGMP
Second generation anti-histamines have a higher or lower lipid: water coefficient
lower
When administered orally, antihistamine drugs are absorbed rapidl
For elimination, the anti-histamine drugs are metabolized in the ____ by ____.
liver, n-methyltransferase
Some antihistamines can be excreted into urine unchanged.
In addition to treating allergies, 1st gen antihistamines also treats and prevents what?
treat nausea, vomiting
prevents motion sickness and vertigo
also induces sedation
The second-gen antihis are mainly used for what?
Treat allergies.
What are the adverse effects of Diphenhydramine and to a lesser extent other First-generation antihis? These effects are similar to what?
sedation
Block muscarinic receptors causing dry mouth, blurred vision, tachycardia, and urinary retention
These effects are similar to atropine side-effects ( know this)
These effects are similar to atropine side-effects ( know this)
What are the adverse effects of Azelastine?
cause dizziness, headache, nasal irritation, dry-mouth, and weight gain.
2nd gen
