The New Second- Generation
Antihistamines
Summer is here and with it’s arrival the
symptoms of allergies sneezing, congestion, runny and itchy nose
(rhinitis), and itchy, red eyes (conjunctivitis).
Approximately 10-20% of the population as a whole has
allergies and a high percentage of allergic individuals is
children. Whether
someone has seasonal (or year-round) allergies depends primarily
on two factors: (1) Genetics- is there a family history of
allergy? (2)
Environmental- is the individual old enough and been exposed to
enough pollen? Allergy
symptoms can be severe and are responsible for the most loss of
time from work and school than any other cause. Fortunately, allergy symptoms are not life threatening and
can be treated and prevented.
Ninety percent of children with asthma however, which can
be life threatening, have allergic triggers for their asthma,
making allergies the second leading cause of asthmatic attacks,
second only to viral infections.
Identifying what one is allergic to, and
avoiding it is desirable but not always possible.
Weeds, for example, pollinate from July through October
and the major fall weed is ragweed.
Avoiding ragweed pollen, however, is not possible and no
one should stop enjoying outdoor activities.
How can we prevent and treat allergies?
For some allergic individuals or patients with asthma, it
may be necessary to stay indoors when pollen counts are high.
Keeping the windows closed and the air conditioner
running can effectively prevent pollen from entering the bedroom
at night or in the morning when pollen counts rise and cause
rhinitis or asthmatic symptoms.
Unfortunately, we currently do not yet have
medications that cure allergies; allergic medications are used
to keep symptoms under control and only help while they are
actively being taken. Allergy medication is most effective if taken on a regular
basis to prevent symptoms.
The maximum benefit from medications occurs after two
weeks of daily use. They are, in that respect, like birth control pills.
Medications must be taken in advance and work only as
long as they are taken.
Antihistamines are indicated as first line
therapy for allergies. They
decrease itching, sneezing and runny nose but do not do much for
congestion unless the antihistamine is combined with a
decongestant. The
older first-generation antihistamines include such medicines as
Chlortrimeton and Benadryl.
They work well, but are very sedating.
The newer second-generation antihistamines have been
available now for years and are just as effective, but there are
differences. Non-sedating
(non-drowsy) antihistamines include Allegra and Clarinex, while
Zyrtec is mildly (approximately 9% patients) sedating.
This can be avoided by taking all doses at night and
staring out with half the dose for a week, followed by a full
dose nightly. Allegra,
Clarinex and Zyrtec are taken once daily.
Allegra and Zyrtec also have decongestants added to their
antihistamine formula to reduce the nasal congestion and can be
taken twice daily for congestion with good results.
All three drugs may be taken with or without meals.
Children’s formulas are available for Zyrtec and
Allegra and will soon be available for Clarinex.
Patients with year-round allergies may
require antihistamines daily all year round.
Those patients with seasonal allergy symptoms may begin
their Allegra, Clarinex or Zyrtec a few weeks before their
“allergy season” and continue then for several weeks after
the season is over.