Anti-Inflammatory Drugs - Regal Flashcards
What inflammatory mediators are involved in redness (due to vasodilation)?
- Histamine
- PGE2
- PGI2
- Kinins
What inflammatory mediators are involved in swelling (due to increased vascular permeability)?
- Histamine
- Peptido leukotrienes (LTC4, LTD4, LTE4)
- Kinins
What inflammatory mediators are involved in pain (causes pain/reduces pain threshold)?
- PGE
- PGI
- LTB4
- Kinins
What inflammatory mediators are chemotactic (direct migration of white blood cells)?
- LTB4 (neutrophils, etc.)
- Peptido leukotrienes (eosinophils)
What inflammatory mediators are involved in fever?
PGEs induce fever
What inflammatory mediators are involved in airway constriction/bronchoconstriction?
- Histamine
- Peptido leukotrienes
- Kinins
- PGD2
What inflammatory mediators are involved in hypotension/decreased blood pressure (relevant in shock)?
- Kinins
- Histamine
What is the pathway for synthesis of Histamine?
- Histidine → Histamine
- via L-histidine decarboxylase
What is the primary site of Histamine synthesis?
- Mast cells
- Basophils
How is histamine inactivated/degraded? Where?
- Histamine → N-methylhistamine
- via N-methyltransferase
- Histamine → Imidazoleacetic acid
- via Diamine Oxidase
- Where
- Enzymes for metabolism are widely distributed
- small intestinal mucosa
- skin
- kidney
- liver
- thymus
- WBCs
- etc.
- Enzymes for metabolism are widely distributed
What are the important biological activities of Histamine as they relate to inflammation?
- Itching/pain
- due to stimulation of nerve endings
- Localized redness
- due to arteriolar dilation
- Localized edema
- due to increased capillary permeability with leakage of the postcapillary venules
- Airway constriction/bronchoconstriction
- stimulates mucous secretion
- vasodilation & edema
- Flare (diffuse redness around/beyond the original redness)
- nerves dilating neighboring arterioles
What is the result of H1 receptor stimulation by Histamine?
- H1
- bronchoconstriction
- contraction of GI smooth muscle
- increased capillary permeability (wheal)
- pruritis (itch) and pain
- release of catecholamines from the adrenal medulla
What is the result of H2 receptor stimulation by histamine?
- Gastric acid secretion
- Inhibition of IgE-mediated basophil histamine release
- histamine release by antigen feeds back to turn off its own release
- Inhibition of T lymphocyte mediated cytotoxicity
- Suppression of Th2 cells and cytokines
Where are H3 and H4 receptors? What effect does histamine have on these?
- Histaminergic nerve terminals (H3)
- Many immune cells (H4)
- eosinophils
- dendritic cell
- T cells
- neutrophils
- Histamine can regulate the activity of all of these cells through stimulating the receptor(s).
What is the general MOA of classical first generation antihistamines?
- Block:
- H1 receptors (inverse agonists)
- muscarinic receptors
- alpha adrenergic
- serotonin receptors
What are the generic names of the two “Old” H1 Antihistamines that we need to know?
- Diphenhydramine (OTC)
- Chlorpheniramine (OTC)
What is the distribution of “Old” H1 Antihistamines?
- Well absorbed orally
-
Widely distributed
- including CNS
- Not recognized by the P-glycoprotein efflux pump on the endothelial cells in the vasculature of the CNS
- i.e. they are not pumped out of the CNS
How are the “Old” H1 Antihistamines eliminated?
- Transformed to inactive metabolites in the liver
- Excreted in the urine
What are the major toxicities of “Old” H1-Antihistamines?
- Sedation
- Drying of secretions (due to anticholinergic properties)
- GI disturbances
- Acute poisoning - treatment is symptomatic & supportive
- resembles atropine poisoning (fixed-dilated pupils, flushing, fever, dry mouth)
- Dominant effect: excitation, hallucinations, incoordination, convulsions
- Terminally: coma & cardiorespiratory collapse
What are the difference between the two “Old” H1 Antihistamines that we need to know?
- Diphenhydramine (OTC)
- low incidence of GI side effects
- sedative
- Chlorpheniramine (OTC)
- most suitable for daytime use
What is the general MOA of “Newer” Non-Sedating Antihistamines?
- Inverse agonist of H1 receptor
- appear as competitive inhibitors of the actions of histamine
- Minimal/No anticholinergic properties
What are the generic names of the three “Newer” Non-sedating H1 Antihistamines that we need to know?
- Cetirizine (OTC)
- Fexofenadine
- Loratadine (OTC)
What is the distribution of “Newer” Non-Sedating H1 Antihistamines?
- Widely distributed
- Penetration into the CNS
- only small amounts cross the BBB
- cause less sedation that first gen
- have affinity for P-glycoprotein efflux pumps in endothelium of vasculatrue in CNS
- pumped out of CNS
What are the major toxicities of “Newer” Non-Sedating H1 Antihistamines?
- Cardiotoxicity with original non-sedating antihistamines
- Cardiotoxicity with overdosage for one of the first non-sedating antihistamines led to the development of the newer drugs that are not cardiotoxic
- Cetirizine
- Fexofenadine
- Loratadine
- Cardiotoxicity with overdosage for one of the first non-sedating antihistamines led to the development of the newer drugs that are not cardiotoxic