Autocoids & Anti-Histamines (final exam) Flashcards
Definition of autacoids
Chemical mediators that function in localized tissue and participate in physiological response to injury
Examples of autacoids
Histamines
Serotonin (5-HT)
Prostaglandin
Peptides
Where are histamines stored?
Throughout the body (lungs, skin, stomach), within mast cells
Histamine release is triggered by:
Immune-induced (type 1 hypersensitivity)
Insect sting / envenomation
Drug-induced
Physical injury
Antihistamines (H1 antagonists)
Diphenhydramine
Hydroxazine
Loratadine
Janus kinase inhibitor
Oclacitinib
Leukotriene inhibitor
Zafirlukast
5-HT inhibitor
Trazadone
Histamine receptors
Histamine-1 (H1)
Histamine-2 (H2)
Effects of H1 agonism
Inflammation
Bronchoconstriction - smooth muscle contraction
Vasodilation - vascular smooth muscle relaxation
Mediate signs of urticarial and pruritis
Effects of H2 agonism
Increased gastric HCl secretion
Vascular smooth muscle relaxation
Anti-histamine drug targets
Mast cell stabilizers (glucocorticoids)
Physiologic histamine antagonists (catecholamines)
Therapeutic histamine antagonists (histamine receptors antagonists)
Anti-histamine mechanism of action
Competitive H1 antagonism
Relaxation of bronchiolar smooth muscle
Inhibits vasodilation
Inhibits pruritis and itch stimulation
Anti-histamine pharmacokinetics
High bioavailability
High Vd
Adverse effects
Sedation is common (first gen more than second gen)
CNS depression
Antimuscarinic signs
Drug tolerance
Drug of choice for allergic reactions
Diphenhydramine
Primarily used to treat type 1 hypersensitivity
Hydroxyzine uses
Primarily used as adjunct in managing allergies
Most effective when administered prior to histamine signs
Poor efficacy for chronic allergic dermatopathies
Loaradine uses
Non drowsy
Little documented animal efficacy
Some human versions contain xylitol
Oclacitinib mechanism of action
Janus-Kinase inhibitor (JAK1 & JAK3)
Inhibits pro-inflammatory cytokines
Inhibits IL-31, sensation of itching
Directly targets pruritis
Oclacitinib use
Treatment of allergic dermatopathy in dogs
Relief possible within 1 hour
Oclacitinib adverse effects
GI signs
Polydipsia
Lethargy
Opportunistic infections possible
Zafirlukast mechanism of action
Leukotriene receptor antagonist
Selective competitive antagonist for LTD4 and LTE4 receptors
Zafirlukast uses
Adjunct treatment for feline asthma
Prevents bronchoconstriction in cats
Trazadone mechanism of action
Serotonin antagonist reputable inhibitor (SARI)
5-HT2A and a1-adrenergic receptor antagonist
Increases serotonin levels in the brain
