Allergy Therapy: Topical Allergy Medications Flashcards
which histamine receptor type is involved in immediate hypersensitivity reaction?
H1
which histamine receptor type promotes gastric acid production & immune cell activation?
H2
which histamine receptor type causes presynaptic feedback inhibition?
H3
which histamine receptor type involves immunomodulation, inflammation, & has nociception roles?
H4
where are H1 receptors more commonly found?
what happens when histamine binds to H1?
nerve endings
triggers the itch response
where are H2 receptors more commonly found?
what happens when histamine binds to H2?
vasculature
causes vasodilation → redness
which hypersensitivity reaction is antibody independent?
type IV
which hypersensitivity reaction is not responsive to antihistamines & most responsive to steroid therapy?
type IV
in type IV hypersensitivity, what is it called when cytotoxic T-cells attach to similar antigens in healthy tissue & destroys it?
autoimmune reaction
H1 & H2 antihistamines are what type of agonists? & what do they do?
inverse agonists → binds to same receptor & modifies the reaction
why is histamine always being produced?
to counteract sympathetic nervous system to prevent complete vasoconstriction
when histamine binds to the active state receptor, what happens?
increased vasodilation & itching
when antihistamines bind to the inactive state receptor, what happens?
inactivation & less histamine is produced
decrease in vascular permeability (less swelling), vasodilation (less redness) & sensory nerve stimulation (less itch) is caused by what mechanism of action?
antihistamines bind to H1 receptor
which antihistamine is highly lipophilic & can therefore enter the CNS (blood-brain barrier) and other tissues readily?
1st generation (classic) antihistamines
which class of antihistamines cause decrease in alertness, cognition, learning, memory & psychomotor performance (dizziness) and increases impairment with or without sedation?
1st generation antihistamines
which class of antihistamines do not readily enter the CNS and therefore have less associated side effects?
2nd generation antihistamines
both classes of antihistamines have what kind of property? and what do they bind to?
anticholinergic properties
bind to muscarinic receptors of the parasympathetic pathway
the anticholinergic properties of antihistamines cause what?
decrease mucous production & tear production, causes mydriasis
oral chlorpheniramine is in which chemical class & what class of antihistamine is it?
1st gen alkylamines
cetirizine (Zyrtec) belongs to which chemical class & which class of antihistamines?
2nd gen piperazines
OTC topical ketotifen belongs to which chemical class & which antihistamine class?
1st gen piperidines
which 1st gen medication is OTC and used for allergic conjunctivitis?
ketotifen
bepotastine, loratadine (Claritin), fexofenadine (Allegra) & alcaftadine are common drugs in which chemical class & which antihistamine class?
2nd gen piperidines
diphenhydramine (Benadryl) belongs to which chemical class & which class of antihistamines?
1st gen ethanolamines
azelastine & olopatadine are which class of antihistamines?
2nd gen
what are oral agents believed to block Ca2+ influx into mast cells (& other immune cells) to prevent degranulation & chemical release?
mast cell stabilizers
mast cell stabilizers are useful for which hypersensitivity reaction?
type I
which one of these topical mast cell stabilizers are fast acting?
- pemirolast 0.10%
- nedocromil 2%
- lodozamide 0.10%
- cromolyn 4%
nedocromil 2%
what allergy medication is an adrenergic agonist & is more effective in binding to α1 receptors than norepinephrine?
decongestants
imidazolines are which class of allergy medications?
decongestants
what occurs when imidazolines are stopped?
rebound effect
what are some OTC imdazolines (decongestants)?
- naphazoline
- tetrahydrozoline
- oxymetazoline
how is brimonidine 0.025% different from imidazolines? & what are its effects?
it is highly selective for α2 receptors (vs α1)
- no rebound congestion, no tachyphylaxis & improved oxygenation
when decongestants are used alone, what does it do for allergies?
- vasoconstriction reduces redness (hyperemia)
- vasoconstriction reduces vessel leakage or tissue
when decongestants are combined with other allergy therapies, what occurs?
- reduce vascular absorption → reduces systemic toxicity
- reduces systemic metabolism/drug clearance
- sustains local effect of applied drugs
how do decongestants cause mydriasis?
because of their α1 sympathetic effects
when are decongestants contraindicated?
in patients with angle closure glaucoma or narrow angles
these drugs are all?
- antazoline + naphazoline (Vasocon-A)
- pheniramine + naphazoline (Visine-A)
- pheniramine + naphazoline (Naphcon-A)
- pheniramine + naphazoline (Opcon-A)
OTC 1st gen antihisamines + decongestants
antihistamine+decongestants have drug interactions with which drugs?
MAOI, EtOH
what are the contraindications for using 1st gen antihistamines + decongestant combos?
- hypersensitivity
- CVD, uncontrolled DM
- narrow anterior chamber angles
- precautionary use with dry eyes
which class of drugs are these?
- ketotifen fumarate 0.035% + imidazoline (Zatidor)
- ketotifen 0.025% + imidazoline (Alaway, Claritin Eye, Zrytec Itchy Eye, Refresh Eye Itch)
acute care OTC 1st gen antihistamines + MCS
1st gen antihistamine + MCS combos are what compared to antihistamines + decongestants?
far more effective & have less side effects
these drugs belong to which class?
- bepotastine 1.5% (Bepreve)
- epinastine 0.05% (Elestat)
- alcaftadine 0.25% (Lastacaft)
- azelastine 0.05% (Optivar)
- olopatadine 0.2% (Pataday)
- olopatadine 0.7% (Pazeo)
acute care 2nd gen antihistamien + MCS
what is Zerviate? what is it used for?
first ever topical formulation of cetirizine 0.24% (2nd gen)
- indicated for allergic conjunctivitis
oral chlorpheniramine (Chlor-Trimeton) is what class of antihistamine? is it mildly, moderately, or strongly sedating?
1st gen antihistamine → mildly sedating
oral clemastine (Tavist) is which class of drug? is it mildly, moderately, or strongly sedating?
1st gen oral antihistamine → mildly sedating
oral diphenhydramine (Benadryl), promethazine (Phenergan) & hydroxyzine (Vistaril) belong to which class of drugs? are they mildly, moderately, or strongly sedating?
1st gen oral antihistamines → strongly sedating
what allows oral 1st gen antihistamines to be sedating?
their lipophilic structures cross the blood brain barrier
what drugs do 1st gen oral antihistamines interact with?
- potassium supplements
- codeine & opioids
- anticholinergics
what is an ocular contraindication for oral 1st gen antihistamines?
angle closure glaucoma
these drugs belong to which drug class?
- fexofenadine (Allegra)
- loratadine (Claritin)
- loratadine + pseudoephedrine (Claritin D)
- desloratadine (Clarinex)
- cetirizine (Zyrtec)
oral 2nd gen antihistamines
2nd gen antihistamines are less likely to cause what even with oral use?
drowsiness
what class of drugs do these belong to? & what are they used for?
- cimetidine (Tagamet)
- famotidine (Pepcid)
- nizatidine (Acid)
oral anti-H2 antihistamines → indicated for GERD & gastric ulcers
what are the two ancillary therapies for allergies?
- NSAIDs
- steroids
which ancillary allergy therapy is most likely to sting?
NSAIDs
which ancillary allergy therapy may cause an increase in IOP & cataract formation?
steroids
under the OTC Code of Federal Regulations, topical 1st gen vasoconstrictors should not be used more than how many times?
4x/day
do topical or oral allergy therapies may require more frequent dosing?
topical
are topical or oral allergy therapies better for deeper ocular involvement?
oral
are topical or oral allergy therapies better for moderate-severe eyelid edema & conjunctival chemosis?
oral
what is the most common site of ocular allergy
conjunctiva
what are the three types of allergic conjunctivitis? what type of hypersensitivity is this?
- acute allergic conjunctivitis
- seasonal allergic conjunctivitis (SAC)
- perennial allergic conjunctivitis
- type I hypersensitivity
what ocular allergy is common in the spring & presents with giant papillae, shield ulcer, & Horner Trantas dots? what type of hypersensitivity is it?
vernal keratoconjunctivitis (VKC) - type I & IV hypersensitivity
what ocular allergy presents with lid eczema & has corneal involvement such as SPK, corneal ulceration, neovascularization, pannus & scarring? what type of hypersensitivity is this?
atopic keratoconjunctivitis (AKC) - type I & IV hypersensitivity
what ocular allergy is associated with CL wear and has a more mechanical etiology than immune? what type of hypersensitivity is this?
giant papillary conjunctivitis (GPC)
- type I & IV hypersensitivity