Term
| Where is histamine stored in the human body? |
|
Definition
in the blood: in basophils
in peripheral tissue: in mast cells |
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Term
| What type receptors are histamine receptors? |
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Definition
| G-protein coupled receptors |
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Term
| What is the primary role of H1 receptors and where are they located? |
|
Definition
allergic inflammation;
smooth muscle, endothelium, brain |
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Term
| What is the primary role of H2 receptors and where are they located? |
|
Definition
gastric acid secretion;
gastric mucosa, cardiac muscle, mast cells, brain |
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Term
| How does histamine cause immediate hypersensitivity? |
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Definition
| repeated exposure to an antigen crosslinks IgE on basophils and mast cells, which cause the release of secretory granules -> histamine constricts bronchioles, decreases BP, increases capillary permeability => anaphylaxis |
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Term
| What are some drugs/stimuli that will cause histamine release without IgE binding? |
|
Definition
- venoms
- morphine
- tubocurarine
- succinylcholine
- cold or tissue injury
- radiocontrast media *can cause anaphylactoid rxns
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Term
What is the endogenous function of histamine in the CNS? |
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Definition
| It acts as a neurotransmitter that modulates sleep cycles, vestibular signals, energy homeostasis; overall, causes sedation and appetite suppression |
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Term
| What type of histamine receptor causes vasodilation when stimulated? |
|
Definition
H1 and H2
(H1 response is more rapid and short-lived) |
|
|
Term
| What is the Triple Response of Lewis? |
|
Definition
- “Red spot”—at injection site due to direct capillary dilation.
- “Wheal”—surrounding the “red spot” due to increased capillary permeability causing loss of proteins and fluid resulting in edema.
- “Flare”—develops 1 cm away due to sensory axon reflex causing arteriole dilation; develops more slowly.
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|
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Term
| How does histamine increase capillary permeability? |
|
Definition
| Stimulation of H1 receptors -> increase separation of endothelial cells -> increased outward movement of proteins and fluid into extracellular space |
|
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Term
| Which type of histamine receptor mediates peripheral pain and itching? |
|
Definition
|
|
Term
| Which type of histamine receptor mediates basal acid secretion from the parietal cells of the stomach? |
|
Definition
|
|
Term
| What are two clinical uses of histamine? |
|
Definition
| Pulmonary function testing and as a positive control in allergy skin testing |
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Term
| How do antihistamines work? |
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Definition
| They are inverse agonists of the H1 receptor: they bind it and keep it in an inactive state |
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Term
| What are the effects of first generation antihistamines on the CNS? |
|
Definition
- sedation
- reduced nausea and emesis associated with motion sickness
- weight gain (cyproheptadine promotes appetite)
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|
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Term
| What are some adverse effects of 1st generation antihistamines? What happens in overdose? |
|
Definition
- anticholinergic effects
- dry mouth
- urinary retention
- diplopia
- confusion
- sedation
- overdose: hallucinations, ataxia, convulsions
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Term
| What is diphenhydramine used for? |
|
Definition
- motion sickness
- extrapyramidal Parkinsonian symptoms from anti-psychotic treatment
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|
|
Term
|
Definition
first generation antihistamine
OTC cold medicine |
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|
Term
|
Definition
first generation antihistamine
OTC cold medicine |
|
|
Term
|
Definition
first generation antihistamine
used in paraplegic spasticity, appetite stimulation |
|
|
Term
|
Definition
first generation antihistamine
motion sickness |
|
|
Term
|
Definition
first generation antihistamine
pruritis, adjunctive pain control |
|
|
Term
|
Definition
first generation antihistamine
motion sickness, dizziness |
|
|
Term
|
Definition
first generation antihistamine
antiemetic, neuroleptic, sedation,
anesthetic adjunct |
|
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Term
| What are the second generation antihistamines in order of low to high sedative effect? |
|
Definition
- fexofenadine
- loratadine/desloratadine
- cetirizine/levocetirizine
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|
|
Term
|
Definition
| nasal preparation used for allergic rhinitis and vasomotor rhinitis |
|
|
Term
|
Definition
| ophthalmologic preparation for allergic conjunctivitis |
|
|
Term
| What are the clinical uses of antihistamines? |
|
Definition
- allergic rhinitis
- chronic urticaria
- emesis and motion sickness
- mastocytosis
- Antiparkinson's effects
|
|
|
Term
| What is the first line of therapy for allergic rhinitis? Why are antihistamines used as well? |
|
Definition
nasal corticosteroids
- antihistamines can be administered orally and have faster onset of action |
|
|
Term
| What is the difference between urticaria and angioedema? |
|
Definition
| Urticaria is mast cell activation in the subcutaneous layer, while angioedema is deeper mast cell degranulation |
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|
Term
| What are two mechanisms of action for corticosteroids? |
|
Definition
- increase transcription of anti-inflammatory mediators
- recruit histone deacetylases to prevent HAT (histone acetyl transferase) from acetylating histones that allow transcription of proinflammatory proteins
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|
Term
|
Definition
mast cell stabilizer
inhibits release of histamine - most effective prophylactically |
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|
Term
|
Definition
mast cell stabilizer
inhibits release of histamine - most effective prophylactically |
|
|
Term
|
Definition
competitive leukotriene antagonist
- relieves allergic nasal congestion |
|
|
Term
|
Definition
antigcholinergic spray
for runny nose (vasomotor or allergic rhinitis) |
|
|
Term
|
Definition
sympathomimetic (alpha agonist)
nasal decongestant
* may cause rebound congestion |
|
|
Term
What is the role of H2 blockers in the age of proton pump inhibitors?
|
|
Definition
| onset of action is quicker than proton pump inhibitors, so these are useful for intermittent quick symptom relief (safe, OTC) |
|
|
Term
| What are the H2 antagonists? |
|
Definition
- cimetidine *adverse effects
- ranitidine
- famotidine
- nizatidine
|
|
|
Term
| What are some adverse effects of cimetidine? |
|
Definition
- antiandrogen
- cytopenia (decrease in platelet count)
- drug interactions (via CYP450 inhibition)
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|
Term
| What are some interventions for anaphylaxis in addition to epinephrine? |
|
Definition
- saline
- methylprednisolone
- albuterol (beta-2 agonist)
- diphenydramine (H1)
- ranitidine or famotidine (H2)
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