The Family Practice Newsletter
Choosing an
Antihistamine
June 2013
Inside this Issue

Choosing an
Antihistamine
**Updated**
Comprehensive
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Erica Townley, PharmD Candidate
Allergic rhinitis is a very common
disease affecting almost 30% of adults
and 40% of children. The symptoms
associated with allergies can be caused
by seasonal “outdoor” allergies or
perennial “indoor” allergies. The most
common seasonal outdoor allergens are
mold, tree, grass and ragweed pollen.
Tree pollen is most common from late
March to May, grass pollen occurs from
May to July and ragweed is present mid
August through the first frost. Perennial
indoor allergens include dust mite
droppings, animal dander, cockroach
droppings and molds. The symptoms
experienced with both indoor and
outdoor allergies are similar and consist
of sneezing, nasal itching, nasal
congestion, and a runny nose. These
symptoms are treated by avoidance of
the allergen altogether and with the use
of antihistamines.
Antihistamines are recommended as the
first-line therapy for allergic rhinitis and
work by blocking the H1 receptors.
There are two different generations of
antihistamines, which have different
characteristics.
First-Generation Antihistamines
Newsletter Contact Information:
Megan Keller, PharmD
MKELLER4@OhioHealth.com
Doctors Hospital Family Practice
2030 Stringtown Road, Suite 300
Grove City, Ohio 43123
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effective. The sedation resulting from
these antihistamines is a major reason
why they are not used as commonly in
therapy.
The first-generation antihistamines
include diphenhydramine
(Benadryl®), chlorpheniramine
(Chlor-Trimeton®), and
brompheniramine (Dimetapp®). All
of these are highly lipid soluble with a
low molecular weight giving them a
high affinity for H1 receptors and other
receptors in the CNS. Due to this
affinity, they are likely to cause
sedation as an adverse affect. Within
this class, chlorpheniramine is the
least sedating and diphenhydramine
is the most sedating but also the most
Second-Generation Antihistamines
Second-generation antihistamines
cause far less sedation because they are
less lipid soluble and have a higher
molecular weight. The secondgeneration antihistamines include
loratadine (Claritin®), desloratadine
(Clarinex®), cetirizine (Zyrtec®), and
fexofenadine (Allegra®). Cetirizine is
the most sedating of the secondgeneration antihistamines. The
efficacies of both first and secondgeneration antihistamines are very
similar but second-generation
antihistamines have been found to
relieve nasal congestion through their
some anti-inflammatory properties.
Second-generation antihistamines are
often preferred over the first-generation
antihistamines due to the less sedating
properties and also the duration of
action. Medications such as cetirizine
and loratadine have to be taken once
daily while the first-generations require
multiple daily doses which are less
convenient for patients. As far as the
onset of action, it has been found that
cetirizine may work up to two hours
faster than loratadine. Another option
for solely preventing seasonal allergies
is cromolyn sodium. This works as a
mast cell stabilizer and should be used
2-4 weeks before allergy symptoms are
expected to start.
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The Family Practice Newsletter – May 2013
All of the antihistamines are available
over-the-counter so cost is an important
aspect to look at when choosing an
antihistamine. The first-generation
antihistamines cost the least per dose.
At Walmart, for a 100-count bottle of
store brand (Equate)
diphenhydramine it is $4. For the
second-generation antihistamines, they
are all similar in price but cetirizine and
loratadine tend to be cheaper because
fexofenadine is not available in generic
at all retail stores. For a 30-count
bottle of Equate (Walmart’s store
brand) fexofenadine at Walmart, the
price is about $13. A 60-count bottle
of loratadine is about $7 and a 45count bottle of cetirizine is about $11.
rhinitis which all have similar
effectiveness. When recommending an
antihistamine, it is important to look at
cost and whether the patient will
require a high level of alertness. If
sedation would be a problem, secondgeneration antihistamines should be
recommended. It is also important to
recognize that all patients do not
respond the same way to each
antihistamine, and those who do not
benefit from one agent may respond
better to another.
Conclusion
In conclusion, there are a number of
different treatment options for allergic
References:
Choosing an Antihistamine
1. Comparison of antihistamines. Pharmacist's Letter/Prescriber's Letter 2008; 24(7):240707.
2. Lehman JM, Blaiss MS. Selecting the optimal oral antihistamine for patients with allergic rhinitis. Drugs 2006; 66:2309-19.
3. Lexi-Comp OnlineTM , Lexi Drugs OnlineTM , Hudson, Ohio: Lexi-Comp, Inc.; May 14, 2013.
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