Antihistaminics Flashcards
____ is a common mediator of itching
histamine
What does histamine induce
- vascular permeablity: running nose, watery eyes, swollen lids, papillae
- induces vasodilation: redness, headache, hypotension, reflex tachycardia
- causes smooth muscle contraction: bronchoconstriction
- stimulates sensory nerves: pain and itching and sneezing
what happens as a result of ag binding to Ab?
degranulation; histamine gets released.
what are the most common sites of ocular allergy
- conjunctiva
- cornea
- lids
List the different types of ocular allergies
- acute conjunctivitis
- atopic conjunctivitis (pt is predisposed to dev allergic conjunctivits bc of hyper allergenic state due to asthma or skin condition)
- contact dermatitis: physical contact of chemical on surface
- seasonal conjunctivitis
- perennial conjunctivitis: year round; high degree of hypersensitivity
- GPC: associated with hard contacts & upper lid
- Vernal conjunctivitis; severe reaction; cornea is also involved
- Urticaria (hives)
What is innate immune response
a non specific generic acute response that lacks immunologic memory and acts near entry points of infection or injury.
What are the two different types of innate immune response? Describe them
- Humoral: Blood based; Non classical complement cascade. Release of cytokines by first responder immune cells.
- Cell mediated: Phagocytes ingest foreign proteins, fungi, pathogens,e tc and secrete cytokines to recruit monocytes and neutrophils.
Describe the adaptive immune response and the two different types
It is an acquired specific response that requires prior exposure to the antigen and features both specificity and memory.
Describe the two different types of adaptive immune response
- Humoral: Exposed APC’s stimulate T cells to mature into helper T cells which cause B cells to transform into Ab producing plasma cells.
- Cell mediated: Exposed APC’s stimulate T cells to mature into helper T cells which facilitate sensitization of killer T cells.
What are the key cells in innate and adaptive immune response?
Innate: Killer T cells and macrophages
Adaptive: Cloned memory B and T cells
What is the response time for innate & adaptive immune response
What are the different types of antigens
- Environmental: Animal dander, ragweed, pollen, dust, insect stings.
- Biological: bacteria, viruses, fungi, parasites
- chemical: Vaccines, drugs, proteins, carbs, metals, food additives
What are the different types of hypersensitivity response
(ACID)
- Type 1: Allergy
- Type 2: Cytotoxic/Ab Mediated
- Type 3: Immune complex
- Type 4: Delayed
What falls under type I hypersensitivity response?
It is IgE based; asthma, latex, bee sting, anaphylaxis, angiodema, urticaria, food allergies, rhinitis, atopic dermatitis
What falls under type IV hypersensitivity response?
Cd4/CD8 (cell mediated) T cell based reactions leading to macrophage activation/lysis resulting in cytokine mediated inflammation.
Conjunctivitis medicamentosa, contact dermatitis, chronic graft rejection, type 1 diabetes, MS, PPD test
Describe the type I hypersensitivity rxn
B cell gets in contact with foreign antigen and clones B cells which takes 3-6 days for this reaction to occur. Once they have generated Ab’s they are passed on to mast cells and basophils. mast cell are in tissue , basophils are in blood. The secondary reaction involves re exposure with the ag. Calcium enters and you get degranulation.
when does immediate type 1 hypersensitivity occur
5-30 min after re exposure
What makes up mast cells/basophils?
- prostaglandins
- leukotrienes
- platelet activating factor
what is the mediator of tissue mast cells and basophils
phospholipase A2
Type IV delayed hypersensitivity is ___ cell based and _____ independent..it is NOT responsive to antihistamines, It takes 2-3 days for development and involves re-exposure (memory) response
T; Ab;
What are some ocular allergy therapies
- Topical decongestants
- Topical antihistamines
- topical mast cell stabilizers
- topical combo drugs
- oral antihistamines
- topical Nsaids/steroids
what do cold compresses do
cause vessels to shrink/constrict they act like decongestants and reduce redness and swelling. (less leaky vessels)
Decongestants are ____ agents and include _____ and tetrahydrozoline which are OTC imidazolines
adrenergic; naphazoline
What are combo actions of decongestants
Reduce vascular absorption:
- reduces sytemic toxicity
- reduces sytemic metabolism/drug clearance
- sustains local effect of applied drugs
What are decongestant indications
allergy induces hyperemia and injection
(Phenylephrine is not used in allergy therapy due to its predilection to produce rebound congestion and with chronic use, conjunctival medicamentosa .
What are adverse effects of decongestants
- blur, epithelial erosions, rebound congestion, upper lid retraction
- mydriasis
- elevated IOP
- Reduced IOP
which decongestant causes mydriasis and elevated IOP
naphazoline
which decongestant causes a reduction in IOP
tetrahydrozoline
H1 and H2 antihisaminics are ______ _____
inverse agonists; they cause the reversal of constitutive receptor activity.
what are the different histamine receptors
H1, H2, H3, and H4
this is a classic histamine receptor that is involved in immediate hypersensitivity reaction
H1
this receptor promotes gastric acid production, immune cell activation
H2
this receptor is involved in pre synaptic feedback inhibition
H3
this receptor is involved in immune modulation, inflammation and nociception roles
H4
What is the dosing for antihistamines
QD, BID, and QID
What are broader ophthalmic indications for the use of antihistamines
- allergic conjunctivitis
- myokymia
- allergic rhinitis
- intraoperative anti miotic
____ is a 2nd generation antihistamine. It is category B and dosed 4 x a day. Paed use is 3 YOA
Emadine
What are serious adverse reactions of emadine
keratitis, corneal infiltrates
what are common adverse reactions of emadine
- headache
- abnormal dreams
- bitter taste
- blurred, dry eyes
- foreign body sensation
- hyperemia, pruritus, lacrimation
What is the antihistamine that has the brand name called Vasocon -A that is combined with naphazoline?
Antazoline
What is similar between the topical OTC antihistamines + decongestants besides 1?
They all have the antihistamine Pheniramine and the decongestant naphazoline and are all dosed 4 x a day, category C and paed use is 6 YOA and all first generation antihistamines.
What are adverse reactions of topical antihistamines + decongestants?
mydriasis, anisocoria, medicamentosa,s reactive hyperemia, lacrimation/dry eye, irritation, pain, photophobia, IOP fluctuation, conjunctival vasoconstriction, headache
what are drug interactions involved with topical antihistamines + decongstants
MAOI, and EtOH
what are contraindications of topical AH + Decongestants
Hypersensitivity, CVD, DM, narrow anterior chamber angles, precautionary use with dry eye
What are mast cell stabilizers
oral agents that are believed to block Ca++ influx that stimulates degranulation; this effects not only mast cells but other immune cells. You take it before symptoms .
What is the clinical use of mast cell stabilizers
halt type 1 hypersensitivity reaction!
Which topical mast cell stabilizer is the fastest acting?
Alocril (brand name)/Nedocromil (generic name); Paed use is 3 YOA and is dosed 2 x a day (bid) instead of qid (4)
What are adverse effects of mast cell stabilizers
- burn/sting
- headache
- dry eye
which topical mast cell stabilizer is the least likely to provoke a problem?
Nedocromil
Which topical antihistamine + MCS combo is the only OTC product?
Ketotifen/Zaditor; Ped use is 3 YOA and is dosed bid
Which MCS + antihistamine combo is 2 YOA for ped use?
bepotastine, alcaftadine, and olopatadine
what are adverse reactions of topical antihistamine + MCS combos
sting, burn, FBS, dry eye, itch, H/A, flu-like syndrome, rhinitis, taste changes, URI associated with Elestat
What are differences/advantages between oral vs topical allergy therapy
Topical: required dosing may be more frequent that oral therapy.
Oral: Better for deeper ocular involvement
Better for moderate to severe eyelid edema & conjunctival chemosis
Which receptor is indicated for GERD, gastric ulcer
H2 receptor antagonists
What are oral formulations of Anti H2 antihistamines
- Tagamet - Cimetidine
- Pepcid - Famotidine
- Axid - Nizatidine
- Zantac - Ranitidine
What is common between all first generation oral antihistaminics
they make you drowsy.
Which oral antihistamine is mildly sedating? moderately sedating? strongly sedating?
- chlorpheniramine
- clemastine
- diphenhydramine (bendaryl) and promethazine
what are first gen drug interactions for oral antihistamine’s
- potassium supplements
- codeine & opioids
- anticholinergics
what are first generation contraindications for oral antihistamines
- peptic ulcer
- prostatic hypertrophy
- bladder obstruction
- Angle closure glaucoma
What are the 2nd generation oral antihistaminics
- allegra - fexofenadine
- claritin - loratadine
- clarinex - desloratadine
- zyrtec - cetirizine
what are ancillary allergy therapies
- NSAIDS
2. steroids
which NSAID is used to treat seasonal allergic conjunctivitis
acular
which steroid is safe for long term therapy of SAC and VKC
lotemax
