Histamine and PONV Flashcards
Exam 1
What is an autocoid?
Biological factors that act like local hormones, have a brief duration, and act near the site of synthesis
Three defining characteristics of autocoid:
1) Act like local hormones
2) Brief duration
3) Act near site of synthesis
T/F: Autocoids act distal to the site of synthesis.
F: they act close to the site of synthesis.
T/F: Autocoids behave similarly to local hormones.
True.
T/F: Autocoids are characterized by a brief duration.
True.
What type of autocoid are we focusing on in this lecture specifically?
Histamines
What is the major difference between autocoids and hormones?
Autocoids can be synthesized by almost every cell, while hormones are only synthesized by specific tissues.
Is histamine a hormone?
No, it is an autocoid, though it behaves similarly to a hormone.
What type of autocoid is histamine?
Endogenous amine
T/F: Histamine is an endogenous amine.
True.
Histamine is a chemical mediator in what immune response?
Inflammatory response
What type of role does histamine play in the inflammatory response?
It is a chemical mediator in the inflammatory response.
What type of cells releases histamine?
Mast cells
Where can mast cells be found?
Skin, lungs, GI tract, basophils
What types of tissues are involved in histamine release? By what means?
Skin, lungs, GI tract, basophils via mast cell secretion
T/F: GI tract tissue releases histamine as part of inflammatory immunoresponse.
True.
Skin, lungs, GI tract, and basophils all secrete:
histamine.
Can histamine cross the blood-brain barrier? What about histamine blockers?
Histamine cannot cross the blood brain barrier, but histamine blockers can.
Histamine causes allergic reaction by what mechanism?
Antigen-antibody response
The antigen-antibody response of histamine causes what?
Allergic reaction
Allergic reactions are mediated by what autocoid?
Histamine (causes inflammation)
How many types of histamine receptors are there?
Three.
Which histamine receptor is involved in respiratory + GI smooth muscle contraction?
H1
Which histamine receptor is involved in increased GI secretion of H+?
H2
Which histamine receptor is involved in pruritis/sneezing?
H1
Which histamine receptor is involved in decreased histamine synthesis and release?
H3
Which histamine receptor is involved with increased HR/ contractility?
H2
Which histamine receptor is involved with nitric oxide release by vascular smooth muscle?
H1
Which muscles contract upon activation of H1 receptors?
GI and respiratory smooth muscle
H1 receptors are responsible for what three actions?
GI and respiratory smooth muscle contraction
Pruritis/ sneezing
Nitric oxide release by vascular smooth muscle
When H1 receptors are stimulated, what is released from vascular smooth muscle?
Nitric oxide
Nitric oxide is released from what when H1 receptors are stimulated?
Vascular smooth muscle
Which types of muscles are directly affected by stimulation of H1 receptors?
GI + respiratory smooth muscle (contracts)
Vascular smooth muscle (release nitric oxide)
Itchy, watery eyes are mediated by which histamine receptor?
H1 receptor
Bronchoconstriction during an asthma attack is caused by activation of which histamine receptor?
H1 receptor
Result of activation of H3 receptor?
Decreased histamine synthesis and release
T/F: activation of H1 receptors causes releases of nitrous oxide from vascular smooth muscle.
False: causes release of nitric oxide from vascular smooth muscle
Activation of H2 receptors cause:
Increased GI secretion of H+
Increased HR and contractility
T/F: activation of H3 receptor is a positive feedback loop that causes increased synthesis and release of histamine.
False; negative feedback loop that causes decreased release and synthesis of histamine
Activation of which receptor is responsible for increased HR during allergic reaction?
H2
Activation of which receptor is responsible for increased H+ secretion in GI tract?
H2 receptor
Which histamine receptors have a direct effect on GI tissues? What are those effects?
H1: increased smooth muscle constriction in GI tract
H2: increased H+ secretion in GI tract
If your patient has watery, itchy eyes and is coughing and sneezing, which histamine receptor is activated?
H1
What is the effect of NO release by vascular smooth muscle w/ activation of H1 receptors?
Vasodilation –> hypotension
Hypotension may occur with an allergic reaction because of:
NO release by vascular smooth muscle, caused by activation of H1 receptors
Of all three histamine receptors, we are mainly concerned with the effects of:
H1 + H2
What are the general cardiovascular effects of histamine release?
Decreased BP (d/t NO release, H1) Increased HR (H2) Increased capillary permeability (H1)
T/F: histamine release may result in increased HR and decreased BP.
True
T/F: histamine release decreases capillary permeability.
False; increases capillary permeability.
How does histamine release affect thee respiratory system? Via which histamine receptor?
It constricts respiratory smooth muscle to cause bronchoconstriction via the H1 receptor.
Which receptor is responsible for labored breathing during an allergic reaction?
H1
What is the dermal reaction to histamine release?
Classic flare and wheal response
The flare and wheal response is what system’s reaction to histamine release?
Derma
How does NO production (H1) affect the vasculature?
It causes local vasodilation and increased permeability.
Which action of histamine release causes local vasodilation?
NO production by vascular smooth muscle
What is the immunological affect of histamine release?
Histamine is a mediator of Type I hypersensitive reaction.
Histamine is a mediator of what reaction?
Type I hypersensitive
Which hypersensitive reaction does histamine mediate?
Type I hypersensitive reaction
How does histamine release affect peak airway pressure?
It increases peak airway pressure.
If your patient displayed a decreased blood pressure, an increased HR, and high peak pressures, what might you expect?
An allergic reaction–symptoms are caused by histamine release.
What four facts must you know about H1 activation?
Occurs at lower concentrations of histamine
Decreased AV node conduction
Coronary artery vasoconstriction
Bronchial smooth muscle constriction
What is the effect of H1 activation on bronchial smooth muscle?
Bronchial smooth muscle constriction
What is the effect of H1 activation on AV node conduction?
Causes decreased AV node conduction.
T/F: Activation of H1 receptors increased conduction at the AV node.
False; it decreases conduction at the AV node.
Activation of H1 receptors decreases conduction at what node?
AV node
Conduction of AV node is reduced when which histamine receptors are activated?
H1 receptors
How does activation of H1 receptors affect the coronary artery?
It causes coronary artery vasoconstriction.
Activation of H1 receptors causes constriction of what major blood vessel group?
Coronary arteries
Coronary arteries vasoconstrict upon the activation of what histamine receptor?
H1
T/F: Activation of H1 receptors occurs at lower concentrations of histamine.
True.
How does concentration level of histamine affect H1 receptors?
H1 receptors are activated at lower concentrations of histamine.
Which histamine receptor causes CV effects?
H2 receptor
Main effects of H2 activation:
CV effects
Catecholamine release
Coronary artery vasodilation
Increased gastric H+ secretion by parietal cells in the stomach
What CV effects does activation of H2 receptors have?
Increased HR/ contractility
Effect of activation of H2 receptors on coronary artery?
Coronary artery vasodilation
Activation of which receptor causes coronary artery vasoconstriction?
Activation of which receptor causes coronary artery vasodilation?
H1
H2
Activation of which histamine receptors results in catecholamine release?
H2
What is the main effect of activation of H2 receptors?
Increased gastric H+ secretion by parietal cells in the stomach
By what mechanism does activation of H2 receptors cause catecholamine release?
Adrenal gland stimulation
H2 activation increases secretion of what by the stomach?
Increases secretion of H+ by parietal cells in stomach.
T/F: H2 receptors increase secretion of H+ by parietal cells in the stomach.
True.
What is the mechanism behind the skin response to histamine release?
Dilated capillaries in affected area
Edema d/t increased capillary permeability
“Wheal” d/t dilated arterioles around edema
Classic mosquito bite/ hives reaction seen in histamine release is d/t what?
Dilated arterioles around edema
What causes edema in histamine release?
Increased capillary permeability
Effect of histamine release on capillaries?
Causes dilated capillaries w/ increased capillary permeability
Dilated arterioles around edema cause what?
Wheals
Increased capillary permeability and dilated capillaries cause what?
Edema
What two things cause edema in a histamine release reaction?
Dilated capillaries
Increased capillary permeability
Histamine antagonists: what will they block?
Edema + pruitis
T/F: histamine antagonists block edema + pruitis.
True.
Histamine antagonists: what won’t they block? How should you treat instead?
Hypotension d/t NO release in vascular smooth muscle; treat via vasoconstriction
T/F: histamine agonists will block edema and pruitis.
False; histamine antagonists block edema + pruitis.
T/F: histamine antagonists will not block hypotension d/t release of NO by vascular smooth muscle cells
True.
Principle effects of H2 receptor activation?
Increased H+ secretion in stomach
Increased HR/contractility
Summarize the actions of histamine antagonists:
They will block pruitis and edema caused by histamine release, but they will not treat the hypotension caused by NO release.
T/F: to stop a histamine reaction, you must block histamine receptors.
False; it will help the reaction, but it will not stop it.
At what receptors do histamine antagonists act?
H1 + H2
At what receptors do histamine antagonists not act?
H3
What type of antagonists are histamine antagonists?
Competitive inhibitors
T/F: histamine antagonists primarily work at H1 + H2 receptors.
True.
How do histamine antagonists work?
They do not block the release of histamine. Instead, histamine is still present and an allergic reaction still occurs, but the histamine antagonists block the bad side effects.
T/F: histamine antagonists prevent the secretion of histamine.
False.
T/F: histamine antagonists aid in diminishing an allergic reaction by blunting the bad side effects of histamine release.
True
Do histamine antagonists inhibit the release of histamine?
No.
What do histamine antagonists block?
Bad side effects caused by histamine release and activation.
By what means do histamine antagonists prevent the bad side effects of histamine release?
Competitive inhibition
T/F: histamine antagonists are well absorbed orally.
True
Histamine antagonists are especially absorbed when adminisitered in what form?
Oral
T/F: histamine receptors work primarily on H1 + H3 receptors.
False: work primarily in H1 and H2 receptors
What are the two types of H1 blockers?
First generation + second generation
What is the primary difference between first generation and second generation H1 blockers?
H1 receptors blocker tend to cross the BBB more easily.
Which type of H1 blocker tends to cross the BBB more readily?
First gen H1
T/F: Second generation H1 receptor blockers are falling out of favor because they tend to cross the BBB.
False: first generation
Besides H1 receptors, what other receptors do H1 receptor blockers activate?
Muscarinic cholinergic
Serotonin
Alpha
Muscarinic cholinergic
Serotonin
Alpha
H1 receptor blockers
What do they have in common?
All blocked by first generation H1 blockers
Which type of blocker causes significant sedation?
First generation H1 receptor blocker
T/F: First generation H1 receptor blockers cause signficant sedation.
True
What receptors do second generation H1 receptor blocker bind w/?
H1 only; no muscarinic cholinergic, alpha, or serotonin
At higher doses, second generation H1 receptor blockers are:
non-competitive
What is the primary benefit to using second generation H1 receptor blockers instead of first generation?
Much less sedative effect
Which type of H1 receptor blockers is non-competitive at higher doses?
Second generation
Which type of histamine receptor blocker only affects H1 receptors?
Second generation
What are the three first generation H1 receptor blockers you are expected to know?
Diphenhydramine
Dramamine
Promethazine
Diphenhydramine is a:
First generation H1 receptor blocker
Dramamine is a:
First generation H1 receptor blocker
Promethazine is a:
First generation H1 receptor blocker
T/F: Diphenhydramine is a second generation H1 receptor blocker.
False: first generation
T/F: Dramamine is a first generation H1 receptor blocker.
True.
T/F: Promethazine is the same type of H1 receptor blocker as diphenhydramine.
True.
Name the second generation H1 receptor blockers that you should know.
Loratadine (Claritin)
Fexofenadine (Allegra)
Another name for Claritin?
Loratadine
Another name for Fexofenadine?
Allegra
Another name for Loratadine?
Claritin
Another name for Allegra?
Fexofenadine
Fexofenadine is what type of H1 receptor blocker?
Second generation
Loratadine is what type of H1 receptor blocker?
Second generation
Which medication tends to cause drowsiness, promethazine or loratadine?
Promethazine
Which medication acts on nothing but H1 receptors, Dramamine or Fexofenadine?
Fexofenadine
Which medication acts on seratonin receptors, Dramamine or Loratadine?
Dramamine
Which antihistamine medications are non-competitive at higher doses?
Loratadine
Fexofenadine
Which antihistamines cause sedation?
Diphenhydramine
Dramamine
Promethazine
Promethazine is used to treat what symptoms?
Nausea/ vomiting
Which drug is primarily used to treat motion sickness or motion-induced nausea?
Dramamine
What is the primary concern w/ second generation antihistamines?
They can prolong QT intervals at high doses.
Which has more side effects, first generation or second generation antihistamines? Why?
First generation because they act on muscarinic receptors
Common side effects of first generation antihistamines?
Somnolence Decreased alertness Slowed reaction time Dry mouth Blurred vision Urinary retention Impotence Tachycardia Dysrhythmias
Which symptoms of fist generation antihistamines are primarily d/t their actions on muscarinic receptors?
Impotence Tachycardia Urinary retention Dysrhythmias Dry mouth Blurred vision
What are four uses of H1 blockers?
They are primarily used to treat anaphylaxis and anaphylactoid reactions, but they also treat rhinoconjunctivitis, bronchospasm,
and motion sickness.
Motion Sickness is treated by what type of histamine receptor blocker?
H1 receptor blocker
What should you give a patient to treat rhinoconjunctivitis?
H1 receptor blocker
By what means do H1 receptor blockers treat motion sickness?
They decrease vestibular and visual input from the brain.
Decreasing vestibular and visual input from the brain assists in treating what issue?
Motion sickness