Anti-histamines and Gastrointestinal Drugs Flashcards
(45 cards)
Where are histamine secreting cells found
most tissues; highest levels in respitory and GI tract.
Mast cells + what it treats
Mediates type 1 anaphylactic, immediate hypersensitivity allergic reactions involving IgE
treats things like: hay fever, red, hot swollen and itchy skin, hives, bronchospasm; or generalized causing anaphylactic shock
What is histamines role in the GI tract
To regulate gastic acid secretion, released by ECL cells.
-H2 receptors on acid-secreting cells
Role of Histamine in peripheral nervous system
-predominantly H1 receptors
-Itch + pain
-stimulation of somatic sensory cortex
Histamine in the CNS
-can act as a neurotransmitter or modulator
its effect: promotes wakefulness through H1 receptors
What histamine receptors are there
H1 + H2
What is its subtype and what do H1 receptors do
Gg: activation od phospholipase C, Calcium mobilization
-brain (excitatory)
-Blood vessels (endothelial cells- release NO, cause dilation of arterial smooth muscle)
-Other smooth muscle contraction
-heart= Increased blood flow
ANTAGONIST: used as treatment for allergic response, vertigo, insomnia
Cardiovasual role H1
Vasodilation of blood receptors
increases vascular permeability
-constricts smooth muscle
-increase heart rate
What is its subtype and what do H2 receptors do
Gs: activation of adenylyl cyclase
Brain (unknown)
-Blood vessels (minor dilation through smooth muscle)
-GI tract (minor increase in rate)
-Heart (minor increase in rate)
ANTAGONIST: used to reduce acid secretion by stomach exocrine glands
What is epinephrine and what does it do
It is a: physiological antagonist
-increases cAMP levels which inhibits Mast cell degranulation
-opposes actions of histamine in smooth muscle: Beta-adrenergic recepts induce bronchial dilation, caso constriction.
-Treatment for anaphylaxis
prevents/reverses cardiac collapse:increases Bp and heart contractility
What are the first generation of H1 receptor antagonists
Diphenydramine (benadryl) = most potent oal antihisamine
Dimenhydrinate (Dramamine): less drowsy, allergy/cold medications, reduces mucus secretions
what do the first generation of H1 receptor antagonists help with
-allergic rhinitis
-hay fever
-itching
-contract dermatitis
-insect bites
-conjunctivitis
-nausea +motion sickness
-NOT indicated for asthma
side effects from 1st generation of H1 antagonists
Antihistamine effects: sedation/sleep induction (from blocking H1)
Antimuscarinic effects-through nonspecific actions on muscarinic receptors
-Sedation (CNS effect): prominent.. tolerance is problem
-Drying of secretioins, urinary retention
-anti-parkinsons through muscarinic antagonism (CNS effect)
Other side effects:
-Topical local anesthetic (block NA+ channel)
-Anti-emetic (some anti-serotonin effects)
Drug interactions of First gen H1 antagonists
Other sedatives, anticholinergics, tricyclic antidepressants
What are the second generation H1 antagonist and how are they different + what do they do
Loratidine (Claritin) and Fexofenidine (allegra)
-Do not cross BBB
Side effects: not sedating, no anti-muscarinic effects
Clinical uses: non-drowsy allergy relief, not effective in motion sickness
Both have good oral bioavailability
What is the parietal cell responsible for
gastric acid secretion. Stimulated by Acetylcholine (M3 receptors) and H2 receptors
Where are parietal cells located
Corpus (body) of the stomach.
-parietal cells
-secrete acid
What do ECL, D, and G cells do (in gastric glands)
ECL: histamine releasing- STIMULATES acid secretion
D cells: somatostatin releasing; INHIBITS acid secretion
G cells: Gastrin releasing- STIMULATES acid secretion by parietal cells
what are some causes of peptic ulcer disease in order from most to least common
-H. pylori infection
-NSAIDS, aspirin
-stress ulcerations
-Zollinger-Ellison syndrome
What is Helicobacter pylori, who found it, and what is its epidemiology, what does it need to survive, and what are its disease mechanisms
a basteria; eradication prevents ulcer recurrence. Discovered by Barry Marshall
-Rought of transmission unclear
-primarily childhood acquired (inversely with SES)
-survives in narrow pH range (needs acidic environment)
-Increased gastric acid secretion
-increased pepsinogen secretion
-decreased mucin secretion
How to get rid of H pylori
-antibiotics
-reduce acid
(proton pump inhibitor, Omeprazole)
(H2 receptor antagonist, Cimetidine)
Omeprazole; dynamics + cokinetics
-proton pump inhibitor (PPI)
-irreversible inhibitor (covalently modifies a chain)
Adverse effects: headache, diarrhea occur infrequently
Pro-drug: requires CYP450 to become active and thus inhibits CYP metabolism of other substrates.. drug interactions
what does phase 1 drug metabolism do
-cytochrome p450 enzymes
-oxidize drugs
-different subtypes
-70% of all drug metabolism
What is the warning on Omeprazole
Do NOT take with Plavix (clopidogrel)
why: Omeprazole occupies the cytochrome p450 enzyme needed to activate clopidogrel
Result: Increased risk of heart attack
