Antihistamines & Autacoid Modifying Agents Flashcards
What are autacoids?
Substances derived from various cell types that exert effects on other cell types within the same region
What are the different classifications of autacoids?
Amines, eicosanoids, and peptide autacoids
Define histamine
- Amine autacoid
- Actions on CNS: mainly promotes wakefulness
- Excreted by basophils and mast cells (CNS and GI tract)
- Critical role in anaphylaxis and allergy
What are the histamine receptors?
- HR1: blood vessels, smooth muscle, lungs, CNS
- HR2: heart and GI
- HR3 and 4: CNS/PNS for 3; bone marrow for 4
What are the effects of histamine on the heart?
Increase HR and contraction
What are the effects of histamine on the resp system?
Smooth muscle contraction
What are the effects of histamine on the GI tract?
Gastric acid secretion
What are the effects of histamine on the blood vessels?
Vasodilation
What are the effects of histamine on the nervous system?
Stimulation of nociceptors and arousal
What are the effects of histamine on the skin?
Reddening, wheal, flare
Histamine causes what in rabbits vs. guinea pigs?
Vasoconstriction (rabbits); bronchoconstriction/death by asphyxiation (guinea pigs)
What causes anaphylactic reactions to occur?
Mast cells and basophils systemically and abruptly release mediators of inflammation; severe allergic reaction
What is the first line of defense for anaphylactic shock?
Epinephrine!
Diphenhydramine
MOI: H1 antagonist
Uses: treat allergic reactions, motion sickness (not as effective in cats); prophylactic for doxorubicin
AE: anticholinergic effects, sedation; may cause paradoxical excitement in cats
Cyproheptadine
MOI: H1 antagonist; non-specific serotonin receptor antagonist
Uses: to treat allergic reactions, stimulate appetite (mostly in cats)
AE: anticholinergic effects; sedation
Meclizine
MOI: H1 antagonist; anticholinergic activity
Uses: antihistamine with antiemetic and sedative effects; treat vestibular disease (vertigo)
AE: sedation
Famotidine
MOI: H2 receptor antagonist
Uses: decreases GI acid production
AE: GI effects
Define serotonin
- Amine autacoid; derived from tryptophan
- NT in brain and periphery
- Synthesized in platelets, gastric mucosa, and brain (raphe nuclei) also in plants
- Modulates mood, emotions, memories in CNS
What are the serotonin receptors and where are they located?
5HT2 - CNS, PNS, smooth mm
5HT4 - GI, CNS
5HT6 - CNS, leukocytes
5HT7 - CNS, GI, bv
5HT1 and 5 - CNS
5HT3 - CNS, PNS
What is the effect of serotonin on the GI system?
Increased motility
What is the effect of serotonin on the blood vessels?
- Vasodilation (due to effects on mediators)
- Vasoconstriction (direct effects on endothelial cells)
What is the effect of serotonin on the nervous system?
Regulation of mood, memory
What is the effect of serotonin on leukocytes?
Activation
Seligiline
MOI: monoamine oxidase B inhibitor
Uses: canine or feline cognitive disorder
AE: vomiting, diarrhea, anorexia, restlessness
Fluoxetine
MOI: SSRI
Uses: OCD, aggression, separation anxiety
AE: vomiting, diarrhea, anorexia
What happens if you use Seligiline with SSRIs?
Excess serotonin concentration - Serotonin Syndrome
Trazadone
Antidepressant
MOI: 5HT2a antagonist, weak SSRI
Uses: treat anxiety, can be used in adjunct w/ other antidepressants
AE: sedation, adverse GI effects
What is Serotonin (5-HT) Syndrome and its effects?
Too much serotonin
High body temp, tachycardia, diarrhea, agitation
