chapter 20: drugs for tx allergic rhinitis dh206: pharmacology lisa mayo, rdh, bsdh copyright ©...

Chapter 20: Drugs for Tx Allergic Rhinitis

DH206: PharmacologyLisa Mayo, RDH, BSDH

Copyright © 2011, 2007 Mosby, Inc., an affiliate of Elsevier. All rights reserved.


Chapter 18 Outline1. Histamine 2. Antihistamines3. Intranasal Corticosteroids


Chapter 18 Outline1. Histamine


Histamine Basics•All human synthesize histamine•Stored in mast cells in intestinal mucosa•Amt released determines person’s response•There are 3 types of histamine in human

body (next slide)


Histamine Basics3 histamine receptors (none have clinical use)

1. H1: located on smooth muscle of GI tract, heart, vein, capillaries, bronchi Vasodilation (↓BP – could lead to hypotension) Bronchoconstriction Pain or itching in cutaneous nerve endings (histamine

binds to receptors on local sensory nerve endings) ↑ production of nasal & bronchial mucus

2. H2: located on brain, stomach, heart, blood vessels ↑ gastric acid secretion Vasodilation

3. H3: on mast cells Stimulation inhibits histamine release


(A): Initial exposure to allergen, IgE produced & binds to mast cells

(B) Subsequent exposure: allergen binds to IgE on the mast cell

(C) Mast cells release histamine, leukotriene, prostaglandin

↓ cause bronchoconstriction, vasodilation, mucus production

ALLERGY RXN


NBQHistamine is released largely in part by:

a. Macrophagesb. Enteroendocrine cellsc. Lymphocytesd. Neutrophilse. Mast cells


2. Antihistamines


Histamine Basics• Antihistamines: Block histamine receptors

▫ H1-blockers used to tx allergic rxns & motion sickness▫ Adverse rxns due to binding of antihistamines on other

organs▫ Anaphylactic rxn

Histamine causes more vasodilation & capillary permeability = leads to a further decrease in BP = then shock & cardiac collapse

Which drug do we give to tx? Why?EPI ANTIHISTAMINEα1-receptors Causes

vasoconstriction (↑BP)

ß2-receptors Cause bronchodilation

Histamine Antagonist

Antagonize bronchoconstriction


NBQSerotonin is a preferred vasoactive mediator with actions similar to those of:

a. Heparinb. Thrombinc. Acetylcholined. Histamine


•Relieve S&S of histamine release in body•These drugs ONLY effective on H1 receptors

in body (H2 assoc. with effects in stomach – CH15)▫Oral▫Parental▫Topical creams, lotions, sprays▫Nasal spray for relief of allergic rhinitis ▫Eye drops for itching, watery eyes

Antihistamines (H1-Receptor Antagonists)


First-generation drugs: adverse rxns related to anticholinergic activity (xerostomia, sedation)


1st-Generation AntihistaminesDiphenhydramine(Benadryl)Chlorpheniramine(Chlor-Trimeton)Hydroxyzine(Atarax, Vistaril)Dexchlorpheniramine(Prolarmine)Promethazine(Phenergan)Clemastine(Tavist)Dimenhydrinate(Dramamine)Meclizine(Antivert)


Second-generation drugs▫Less anticholinergic activity: not as many

adverse rxns


2nd-Generation Antihistamines

Fexofenadine(Allegra)

Cetirizine(Zyrtec)

Loratadine(Claritin)


Allegra &

Claritin 2nd gen.



ACTION EFFECTS IN BODY DRUGSAntihistamini

c ActionAllergy relief Relieve itching

Benadryl is most effective

Anticholinergic Action

Sedation, Dry up secretionsBronchodilationDilate eyesRelieve vertigo & motion sickness

Meclizine(Antivent,Bonine)Promethazine(Phenergan) Dimenhydrinate(Dramamine)

Adverse Rxns related to these effects


Intranasal antihistamines▫All intranasal’ s usually taken in combo with oral

sinus med


Intranasal AntihistamineAzelastine(Astelin) Allergic rhinitisOxymetazoline(Afrin)Phenylephrine(Sinex)

α1-antagonist: constrict blood vessels3-5 days after use – will have re-bound action & symptoms worse than before

Olopatadine hydrocholoride(Patanase)

Allergic rhinitis

Board Alert!


NBQWhich of the following adverse effects occurs with antihistamines?

a. Dry mouthb. Increased salivationc. Dry skind. Moist skin


NBQWhich of the following antihistamines has anticholinergic effects?

a. Loratadineb. Fexofenadinec. Diphenhydramined. Azelastine


3. Intranasal Corticosteroids


Intranasal CorticosteroidsIntranasal CorticosteroidBudesonide(Rhinocort)Ciclesonide(Omnaris)Fluticasone propionate(Flonase)Mometasone furoate(Nasonex)

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chapter 20: drugs for tx allergic rhinitis dh206: pharmacology lisa mayo, rdh, bsdh copyright ©...

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