Pharmacology Allergic Rhinitis

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Antihistamines Central (diphenhydramine/benadryl) (first generation)

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-sedation (CNS depression like reaction time slowed, alertness diminished, drowsiness); anticholinergic properties

-H1 antagonist-selective blockade of H1 receptors--reduce localized flushing, capillary beds-prevent increase in permeability so less edema, reduce itching and pain, suppresses secretion of mucus

-mild allergy, severe allergy adjuncts, motion sickness, insomnia, not common cold-moderate reduction rhinorrhea from anticholinergic properties not H1 blockade

-oral-mild to moderate allergic disorders; parenteral-allergic reactions to blood or plasma; adjunctive therapy of anaphylaxis

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Antihistamines Central (diphenhydramine/benadryl) (first generation)

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-sedation-in evening and exercise extreme caution when driving or doing other hazardous activities, dizziness, incoordination, confusional states, fatigue, GI effects-with food, anticholinergic effects-caution with asthma; suck on candy or frequent sips of liquid, urinary retention, prostatic hypertrophy, HTN; elderly especially to CNS and anticholinergic effects

-alcohol and other CNS depressants-warn against drinking alcohol-second gen=less

-toxicity-reduce absorption by giving activated charcoal then cathartic; hyperthermia with ice packs or cooling sponge paths; convulsion with IV phenytoin; like atropine poisoning-tachycardia, dilated pupils, flushed face, hyperprexia, dry moth, urinary retention
-not really preggos or lactation; caution in young kids, elderly and pts with conditions that may be aggravated by muscarinic blockade

-with food if GI upset, not crush/chew enteric-coated

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Peripheral acting antihistamines (second generation) (fexofenadine/allegra 12+, loratadine/claritin 6+)

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-not cross BBB much, so less sedation/CNS depression than first generation

-anticholinergic properties less than first generation

-H1 antagonist-selective blockade of H1 receptors--reduce localized flushing, capillary beds-prevent increase in permeability so less edema, reduce itching and pain, suppresses secretion of mucus

-mild allergy, severe allergy adjuncts, motion sickness, insomnia, not common cold-moderate reduction rhinorrhea from anticholinergic properties not H1 blockade

-oral-mild to moderate allergic disorders; parenteral-allergic reactions to blood or plasma; adjunctive therapy of anaphylaxis

-sedation-in evening and exercise extreme caution when driving or doing other hazardous activities, dizziness, incoordination, confusional states, fatigue, GI effects-with food, anticholinergic effects-caution with asthma; suck on candy or frequent sips of liquid, urinary retention, prostatic hypertrophy, HTN; elderly especially to CNS and anticholinergic effects

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Peripheral acting antihistamines (second generation) (fexofenadine/allegra 12+, loratadine/claritin 6+)

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-alcohol and other CNS depressants-warn against drinking alcohol-second gen=less

-toxicity-reduce absorption by giving activated charcoal then cathartic; hyperthermia with ice packs or cooling sponge paths; convulsion with IV phenytoin; like atropine poisoning-tachycardia, dilated pupils, flushed face, hyperprexia, dry moth, urinary retention
-not really preggos or lactation; caution in young kids, elderly and pts with conditions that may be aggravated by muscarinic blockade

-with food if GI upset, not crush/chew enteric-coated

fexofenadine/allegra: seasonal allergic rhinitis and chronic idiopathic urticaria; dose reduced with those who have renal impairment
loratadine/claritin: seasonal allergic rhinitis; food delays absorption; extensive hepatic metabolism; reduced dosing for those with significant hepatic or renal impairment

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Sympathomimetics (Decongestants) oxymetazoline/afrin, phenylephrine/neo-synehrine, pseudoephedrine/sudafed (2-6 years, except afrin)

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reduce nasal congestion by activating alpha 1 adrenergic receptors on nasal blood vessels-vasoconstriction-shrinkage of swollen membranes followed by nasal drainage; allergic rhinitis-only relieve stuffiness; reduce congestion associated with sinusitis and colds

-adverse effects:rebound congestion when topical used more than a few days-use for 3 to five days and not with those who have chronic rhinitis; oral-CNS stimulation; HTN or CAD, vasoconstriction is bad (oral usually); hemorrhagic stroke-other alpha agaonists? like pseudoephedrine?; abuse with pseudoephedrine and ephedrine- 9 g per month or 3.6 gram per day

pseudoephedrine/sudafed: orally; some CNS stimulation, less than ephedrine, more effective than phenylephrine

2 sprays= topical-no more than 5 days, not as good as drops-act faster and usually more effective than the one oral; oral act longer; systemic effects like vasoconstriction and CNS stimulation occur mostly with oral or high dose topical

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Intranasal Glucocorticoids beclomethasone 12+(vancenase), fluticasone (flonase)12+, budesonide 12+ (rhinocort)

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-most effective drugs for prevention and treatment of seasonal and perennial rhinitis; can prevent or suppress all major symptoms of allergic rhinitis-congestion, rhinorrhea, sneezing, nasal itching, erythema-because of safety and superior efficacy, now joined H1 antagonists as first line therapy

-drying of nasal mucosa and burning or itching sensation; sore throat, epistaxis and headache may also happen
-systemic effects rare-adrenal suppression and slowing of linear growth in children
-take a few weeks to take effect
-after under control, dose should be reduced to lowest effective amount
-use topical decongestant first