Antihistamine Flashcards
Describe Histamine
biogenic amine. central role in the immediate hypersensitivity and allergic responses. Rapidly inactivated after release into blood and tissues.
stored in secretory granules in Mast cells, ECL cells of fundus and stomach.
What is Histamine’s Effect on the Nervous System?
Nerve bodies in hypothalamus to all areas of brain. Regulates Wakefulness, Pit Hormones, appetite, itch
H1 - Peripheral neurons - Epidermis - Itch; Dermis-Pain
What is Histamine’s Effect on the Cardiovascular System?
Vasodilation, fall in B/P. Both H1 and H2
Vasoconstriction in some venous beds - edema
Increased vascular permeability - H1 (cont endothelium disrupts tight junctions, leak)
H2 - Inc Ca2+ leads to inc contraction, SA node inc HR
What is Histamine’s Effect on the Pulmonary System?
H1 in Lung smooth muscle - inc secretion, bronchoconstriction
What is Histamine’s Effect on the Immune System?
Increases Vasc permeability, adhesion molecules, CHemotaxis, Inflammatory cytokines, antigen presentation of apc’s
Helps immune function.
What are the characteristics, effects, side effects and uses of H1-antihistamines?
Examples?
Reversibly bind to Receptors and stabilize the Inactive form.
Treat: allergiic rhinitis, conjunctivitis, Urticaria; N/V;Motion sickness; Sedatives; Sleep aid; cough; cold
What drugs have the strongest anticholinergic actions?
Promethazine
What are the characteristics, effects, side effects and uses of H1-antihistamines?
Examples?
Reversibly bind to Receptors and stabilize the Inactive form.
Treat: allergiic rhinitis, conjunctivitis, Urticaria; N/V;Motion sickness; Sedatives; Sleep aid; cough; cold
At high doses has anticholinergic effects
Which Histamines are first and second generations?
1st: Chlorpheniramine, Diphenhydramine, Pyrilamine, Hydroxyzine, Meclizine, Promethazine, Cyproheptadine
2nd: Azelastine, Fexofenadine, Loratadine, Desloratadine, Levocetirizine, Cetirizine
What is the difference between first and second generation H1 antihistamines?
H1: reversible receptor inhibitor, nonselective, Higher lipophilicity
H2: bind non competitively to H1 receptor, lower lipophilicity means doesn’t cross BBB (less sedating), higher selectivity toward H1 receptor.
What drugs have the strongest anticholinergic actions?
H1 antihistamines: diphenhydramine, promethazine
What drugs have the strongest sedative actions?
H1 antihistamines: Diphenhydramine, Hydroxyzine, Promethazine
What drugs have the strongest antiemetic/antimotion sickness actions?
H1 antihistamines: Diphenhydramine, Promethazine, Hydroxyzine, Meclazine
What drugs have the weakest anticholinergic actions?
H1 antihistamine 2nd gen
What drugs have the weakest sedative actions?
H1 antihistamine 2nd gen: Loratadine, Fexofenadine
What drugs have the weakest antiemetic/antimotion sickness actions?
H1 antihistamine 2nd Gen
What drugs are the strongest inhibitors of serotonin receptors?
H1 antihistamines; cyproheptadine, wt gain, inc appetite
What drugs are the strongest inhibitors of alpha-adrenergic receptors?
H1 antihistamine: promethazine, dizziness, postural hypotension
MOA: Chlorpheniramine
1st gen. Moderate sedating, Moderate antimuscarinic activity, little anti-emetic function.
allergic rhinitis mostly
MOA: Diphenhydramine
1st gen. benadryl
Signif sedation, signif antimuscarinic, signif antiemetic
cough, motion sickness, extrapyramidal symptoms from antipsychotic drugs
blocks Na channels in excitable membranes
MOA: Pyrilamine
1st gen
Low to moderate sedative action, Little muscarinic, no anti emetic activity
Weak sleep aid
MOA: Hydroxyzine
1st gen. marked sedation/antimuscarinic.
primarily an antiemetic/sedative
MOA: Meclizine
1st gen. Minimal antimuscarinic. less sedation than hydroxine
Motion sickness in vertigo
MOA: Promethazine
1st gen. Strong antiemetic/motion sickness.
blocks Na channels. inhib alpha 1 adrenergic receptors.
can block dopamine receptors
MOA: Cyproheptadine
1st gen. Low sedation/antimuscarinic. Serotonin receptor antagonist
SE: inc wt gain, appetite. Tx serotonin syndrome
MOA: Loratadine
2nd gen
MOA: Desloratadine
2nd gen
MOA: Levocetirizine
2nd gen
MOA: Cetirizine
2nd gen
MOA: Cetirizine
2nd gen. out of this generation, this has the most sedation.
MOA: Azelastine
2nd gen. inverse agonist. Reduce Mast Cell release.
Intranasally or in eyes
MOA: Cromolyn
Mast cell stabilizer. Prophylactic tx of allergy. inhib chloride channels
MOA: Nedocromil
Mast cell stabilizer. prophylactic tx of allergy. Inhib chloride channels
MOA: Doxepin
antidepressant. inhib H1 and H2 receptors.
Urticaria
MOA: Ketotifen
Stabilize mast cells. eye drops
MOA: Omalizumab
Monoclonal IgE antibody. Prophylactic tx of allergy, asthma, chronic urticaria.
Binds to free IgE ab and prevents binding of FcE3b on mast cells. reduce cytokines released from mast cells
