Antihistaminesin Skin Disease and Care- Competitive inhibitor (reversible) of histamine at tissue receptor sites; H1 and H2 blockers
- H1 antihistamines divided into first and second generation
- First generation: diphenhydramine, promethazine, cyproheptadine, chlorpheniramine, hydroxyzine
- SE: drowsiness and anticholinergic symptoms (blurry vision, urinary retention, dry mouth, constipation)
- Cyproheptadine: treatment of choice for cold urticaria
- Chlorpheniramine: safest in pregnancy
- Hydroxyzine: side effects include EKG changes, arrhythmias
- Second generation: fexofenadine, loratidine, cetirizine, levocetirizine
- SE: drowsiness and anticholinergic symptoms
- Fexofenadine: few sedative effects, few to no anticholinergic symptoms, category C
- Loratidine: long-acting, minimally sedating, category B
- Cetirizine: low sedation, metabolite of hydroxyzine, ± anticholinergic effect, category B
- H2 antihistamines (cimetidine, ranitidine)
- Cimetidine: competitively inhibits DHT at androgen receptor site (side effects include gynecomastia, impotence, loss of libido)
- Others
- Doxepin: tricyclic antidepressant, H1/H2 antihistamine, inhibits histamine and acetylcholine, anticholinergic, cardiotoxic (may prolong QT interval); side effects: conduction disturbances, seizure disorder, urinary retention
- Amitryptaline: tricyclic antidepressant with some H1 blocking activity, side effects include anticholinergic symptoms and risk of cardiac arrhythmias
- Cromolyn sodium: blocks mast cell degranulation
- Montelukast, zafirlukast: leukotriene receptor antagonist
- Zileuton: inhibitor of 5-lipoxygenase, which subsequently inhibits leukotriene formation
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