Histamines Flashcards
Local hormone, chemical mediators that the body releases as a response to pathogens or noxious substances.
Autocoids
Autocoids: Amine types
Histamines and Serotonin
Type of Autocoids site production are GIT, kidneys, lungs, pancreas and uterus. And physiological actions.
Endogenous type or Ecosonides:
Prostaglandins-pain, inflamm
Thromboxane- platelet aggre
Prostacyclin- inhibition of platelet aggre
Leukotrienes- inflamm, chemotactic properties
Bradykinin
Antihistamines SAR.
Ethanol amine- lipid soluble
tertiary amine- sedation
aromatic rings- hydrophobic
2nd and 3rd generation drugs and derivatives.
2nd: Piperazine: Cetirizine
Piperidine: Fexofenadine and Loratadine
3rd: Piperadine: Desloratadine
Metabolism of Loratadine Hydroxyzine and Terfinadine
Loratadine to Desloratadine
Hydroxyzine to Cetirizne
Terfinadine to Fexofenadine
The only antihistamine not to be used during pregnancy and why?
Bromopheniramine- teratogenicity
1st generation H1 antagonist.
Higher sedation (3* amine), anticholinergic SEs lipid soluble= can cross BBB Anti-serotonin Anti-bradykinin Usually QID
2nd generation H1 antagonist.
Less sedation due to less lipid soluble can’t cross BBB
NO anticholinergic SEs
DI: Terf and Astemizole cardiac arrhythmias due to QT interval
GFJ reduces oral bioav of Fexofenadine
Relieves eye itching, congestion of conjunctiva and erythema. Drug examples.
Topical antihistamines: Olopatadine, Levocabastine, Emedastine, Kitotifen and Azelastine
Present on parietal cell, produces HCl secretions, inc. gastric acid secretion, pepsin and intrinsic factor (Castle’s factor)
H2 receptor antagonists (H2RA)
H2RA drug examples.
Ranitidine, Cimetidine, Famotidine and Nizatidine (-tidines)
Cimetidine SEs
GYNECOMASTIA, mild diarr, constipation HE myalgia confusion hallucinations and excitement
