#4 Antihistamines 9-15-06
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- common feature of autacoids?
- the ability to be formed by certain tissues, and then act on those SAME tissues
- Histamine is found in all tissues, especially high [ ] in?
-
1) lung
2) skin
3) intestinal mucosa - histamine is synthesized from ?
- histadine
- histamine is stored intracellularly in vesicles with?
- heparin
- storage sites of histamine?
-
1) mast cells & basophills
2) GI mucosa
3) nerve endings in certain areas of the brain
4) cells of rapidly growing or regenerating tissue - release of histamine is caused by?
-
1) allergic reactions
2) cellular injury
3) drugs (opioids, sux, contrast, vanc, anti-protozoal) - activation of H1 receptor causes?
- constriction of bronchi and gut
- H2 receptor ?
- gastric acid secretion
- H1 and H2 receptors?
- vascular dilation
- H3 receptor?
- inhibition of histamine release and synthesis (like autoreceptor)
- circulatory effects of histamine?
-
1) increased capillary permeability
2) vasodilation
3) triple response of Lewis - triple response of Lewis?
-
1) red spot
2) wheal
3) flare or red flush - hyposecretion of histamine?
-
1) pernicious anemia
2) gastric carcinoma
3) atropic gastritis - hypersecretion of histamine?
-
1) diodenal ulcer
2) Zollinger-Ellison syndrome - clinical use of histamine for diagnosis?
- Histalog (histamine analog Betazole) = less H1 receptor activity (H2:H1 = 10:1)
- Impromidine?
-
investigational drug
greater H2 selectivity
(H2:H1 = 10,000:1) - 1st generation antihistamines
-
1) Alkylamines
2) Ethanolamines
3) Ethylenediamines
4) Phenothiazines
5) Piperazines
6) Piperidines
7) Phthalazinone - 1) Alkylamines
-
1) Brompheniramine (in Dimetane)
2) Chlorpheniramine (Chlor-Trimeton)
3) Dexchlorpheniramine (Polaramine)
4) Triprolidine (Actifed) - Alkylamines have marked potential for producing?
- sedation
- 2) Ethanolamines
-
1) Carbinoxamine (Rondec)
2) Clemastine (Tavist)
3) Dimenhydrinate (Dramamine)
4) Diphenhydramine (Benadryl)
5) Doxylamine (Unisom) - Clemastine (Tavist) also blocks?
- at muscarinic receptors
- Dimenhydrinate (Dramamine) is used to treat?
- motion sickness
- Dephenhydramine (Benadryl) is active metabolite of?
- dimenhydrinate
- Benaryl
-
1) sedation
2) motion sickness
3) anticholinergic - Doxylamine (Unisom) is used as ?
- OTC sleep aid
- 3) Ethylenediamines
-
1) Tripelennamine (PBZ)
2) Pyrilamine (in cold medecine) - 4) Phenothiazines
- 1) Promethazine (Phenergan)
- Phenergan also blocks at?
- alpha adrenergic receptors
- 5) Piperazines
-
1) Hydroxyzine (Vistaril, Atarax)
2) Meclizine (Bonine OTC, Antivert) - Meclizine is used to treat?
-
1) motion sickness
2) vertigo
3) Meniere's syndrome - 6) Piperidines
-
antihistaminic / antiserotogenic
1) Cyproheptadine (Periactin) - SE of Cyprohepatidine?
- increase appetite and wt gain
- 7) Phthalazinone
-
1) Azelastine (Astelin)
- 1st antihistamine nasal spray
- for seasonal allergic rhinitis - 2nd generation antihistamines
-
1) Loratadine (Claritine)
2) Desloratadine (Clarinex)
3) Cetirizine (Zyrtec)
4) Fexofenadine (Allegra) - benefit of 2nd generation antihistamines?
- non-sedation
- primary active metabolite of Claritin?
- desloratadine (Clarinex)
- Are H1 antagonists effective in severe hypersensitivity reactions?
- No. b/c hypotension is cauused by histamine acting at both H1 and H2 receptors
- antihistamine and MAOI?
- MAOI can prolong and intensify their anticholinergic effects
- episodes of syncope in pts with H1 antagonists?
-
Discontinue H1 antagonists.
SE = severe arrhythmia - H2 receptor antagonists
-
1) Cimetidine (Tagamet)
2) Ranitidine (Zantac)
3) Famotidine (Pepcid)
4) Nizatidine (Axid) - H2 receptor antagonists inhibit?
- action of histamine at parietal cell H2 receptors = decrease in acid secretion
- SE of Cimetidine?
- 1) gynecomastia
- Cimetidine decreases metabolism of?
-
1) Warfarin
2) Phenytoin
3) Theophyllin