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Citrizine Zyrtec 5 or 10 mg once/d
Zyrtec-D Cetirizine 5 mg,
pseudoephedrine 120 mg;
1 tablet bid
Desloratadine Clarinex 5 mg once/d
Fexofenadine Allegra 60 mg bid or 180 mg
once/d
Loratadine Claritin 10 mg once/d
Claritin
Reditabs
Alavert Loratadine 5 mg,
Claritin-D pseudoephedrine 120 m;
1 tab qAM
Leukotriene Modifier
Montelukast Singulair 10 mg once/d
D.Antihistamines
1.Antihistamines are clearly less effective than topical
nasal steroids. Antihistamines typically reduce itching,
sneezing, and rhinorrhea, but may not completely
eliminate the symptoms of nasal congestion.
2.Two second-generation antihistamines are currently
available in syrup for young children. Cetirizine (Zyrtec)
is approved for children >6 months of age. Loratadine
(Claritin) is approved for use in children >2 years of age
and is available over the counter. Second-generation
antihistamines and nasal corticosteroids are not
approved for children under two and three years of age,
respectively. Rondec (carbinoxamine maleate-
pseudoephedrine) drops are approved for children one
month and older.
3.In relieving symptoms, second-generation drugs are
less efficacious than corticosteroids and equally or
more efficacious than cromolyn. The addition of
antihistamines to topical nasal steroids may be useful
in patients with concomitant allergic conjunctivitis. Oral
antihistamine combinations that contain the deconges-
tant, pseudoephedrine, provide better symptom relief
than that associated with antihistamine alone.
4.Adverse effects.
a.First-generation antihistamines easily cross the
blood brain barrier and cause sedation, making
them relatively less desirable. Sedation occurs
uncommonly with second-generation antihistamines
other than cetirizine and azelastine.
b.Metabolites of second-generation antihistamines,
such as the metabolite of terfenadine, fexofenadine
(Allegra), and desloratadine (Clarinex) are classified
as third-generation antihistamines. These com-
pounds avoid potential cardiotoxic effects of the
second-generation compounds.
c.Cetirizine, fexofenadine, desloratadine, and
loratadine have not been associated with QT
prolongation. However, coadministration with P450-
active drugs increases loratadine levels. In addition,
licorice ingestion prolongs QT-intervals and may
potentially have additive effects.
5.Second-generation antihistamines may be preferable
in patients with mild symptoms, or those preferring pills
over nose sprays, especially if allergic conjunctivitis is
also present. Cetirizine (Zyrtec) is reserved for those
who fail loratadine (Claritin) or fexofenadine (Allegra),
as cetirizine has sedative properties.
E.Cromolyn and nedocromil decrease allergic inflamma-
tion by inhibiting mast cell mediator release. Cromolyn, but
not nedocromil, is available in the United States. Cromolyn
is less effective than topical nasal steroids.
F.Allergen immunotherapy
1.Allergen immunotherapy involves the subcutaneous
administration of increasing doses of therapeutic
vaccines of allergens.
2.Efficacy. Allergen immunotherapy to tree, grass and
ragweed pollens, Alternaria mold and house dust mite
is efficacious in allergic rhinitis. Immunotherapy should
be considered in patients in whom pharmacotherapy
and avoidance of allergens have failed to resolve
symptoms.
References: See page 255.
Allergic Conjunctivitis
Allergic conjunctivitis is estimated to affect 20 percent of the
population on an annual basis. Allergic conjunctivitis is
associated with itching, tearing, redness, burning,
photophobia, and mucus discharge.
I.Pathophysiology
A.Allergic conjunctivitis has an average age of onset of 20
years of age, and is principally a disease of young adults.
Symptoms tend to decrease with age.
B.Acute allergic conjunctivitis is an acute, hypersensitiv-
ity reaction caused by environmental exposure to allergens.
It is characterized by intense episodes of itching, hyper-
emia, tearing, chemosis, and eyelid edema. It resolves in
less than 24 hours.
C.Seasonal allergic conjunctivitis (SAC) is also known
as allergic conjunctivitis. It is frequently associated with
rhinitis. It occurs in the spring and late summer, and it is
caused by exposure to pollen, grasses, and ragweed.
D.Perennial allergic conjunctivitis (PAC) is a mild,
chronic, allergic conjunctivitis related to environmental
exposure to year-round allergens such as dust mites and
mold.
E.Acute allergic conjunctivitis, seasonal allergic conjunctivi-
tis (SAC), and perennial allergic conjunctivitis (PAC) are
referred to as "allergic conjunctivitis," and result from
allergens.
II.Clinical evaluation
A.Allergic conjunctivitis is frequently associated with atopy,
allergic rhinitis, skin allergies, and asthma.
B.Signs and symptoms of allergic conjunctivitis include
itching, tearing, conjunctival edema, hyperemia, eyelid
edema, watery discharge, burning, and photophobia.
Symptoms are usually bilateral. The differential diagnosis
includes infectious conjunctivitis, blepharitis, and dry eye.
C.Acute allergic conjunctivitis occurs rapidly upon exposure
to an allergen, such as cat dander. Symptoms can be
severe and debilitating but resolve quickly, usually within
24 hours of removal of the allergen. Seasonal allergic
conjunctivitis typically has a less dramatic onset; it will have
a more predictable and chronic course that corresponds
to the ragweed (late summer and early fall), grass (sum-
mer), and pollen (spring) seasons.
D.Laboratory findings. The diagnosis of allergic conjuncti-
vitis is usually made clinically; therefore, laboratory testing
is not typically performed.
III.Treatment of allergic conjunctivitis
A.Avoidance of the allergen is recommended. Preventive
steps to reduce symptoms of SAC include limiting outdoor
exposure during high "counts" of pollen and ragweed, use
of air conditioning, and keeping windows closed. For those
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