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Antihistamines (Receptors
H1
H2 (H1 Receptors
1) Vasodilation
2)…
Antihistamines
Receptors
H1
H2
H1 Receptors
- 1) Vasodilation
2) Increased capilary permeability
3) Bronchoconstriction
4) CNS Effects - cognition, memory, sleep/wake
5) Itching, pain and secretion or mucus
-
H2 Receptors
- 1) Secretion of Gastric acid
act on parietal cells to promote acid release
2) Dominant Role in Acid release
H2 Antagonists used to selectively block H2 receptors
Used for the treatment of Gastric and Duodenal Ulcers
Role of Histamine in Mild Allergic Response -
Rhinitis, itching, localized edema (swelling of skin)
Role of Histamine in Severe Anaphylactic Reaction
- Limited Role
- Leukotrienes are principle mediators
- Antihistamines are of little use and Epinephrine is used
Pharm Effects
Peripherally
Reduces symptoms (itching, flushing, and pain)
Centrally
Therapeutic
CNS Depression (tiredness, drowsy, etc)
Toxicity/ OD
- 1) CNS Stimulation (hyper activity.....
2) Convulsions
no antidote
Activated Charcoal
Cathartic (flush system)
hyperthermia
for convulsions - IV benzodiazepines