Nasal Allergy Medications (cont.)

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Antihistamines have an interesting history. Bovet and Straub at the Pasteur Institute discovered the first antihistamine in 1937. It was too weak, however, and caused many side effects. In 1942, phenobenzamin (Antegan) was the first antihistamine used to treat allergies. Within a few years, diphenhydramine (Benadryl) and tripelennamine (PBZ) were formulated. These were the first and oldest generation of antihistamines

Many of the older antihistamines are now available OTC. Many different preparations are available, and are derived from six separate chemical classes. Although these inexpensive OTC drugs are helpful in controlling milder symptoms, they also cause various side effects. Drowsiness and reduced mental alertness are particularly common (seen in up to 50% of those taking the medications). Cells that line the blood vessels in the brain regulate which chemicals can enter the brain. These cells are referred to as the blood brain barrier. The reason these drugs induce sleepiness is that they are able to cross the blood brain barrier. The next table lists some common first generation antihistamines; these are widely available and may help people with nasal allergies sleep at night, but should not be used by people who need to be alert (driving vehicles or doing any action that involves high mental concentration) because they can be sedating.

Common First Generation Antihistamines
Generic Name Brand Name
diphenhydramine Benadryl
chlorpheniramine Chlortimeton, Allerest
clemastine fumarate Tavist-1
dexbrompheniramine Drixoral
hydroxyzine Atarax, Vistaril

Asking the pharmacist for generic version of the doctor's brand name suggestion or prescription requires caution. Check that the generic name and strength is the same as the medicine doctor recommended or prescribed.

The second generation antihistamines are often referred to as "non-sedating." In general, this group of antihistamines is more expensive, has a slower onset of action, is longer acting, and induces less sleepiness. However, even some of these can be slightly sedating, so the persons taking these medications should use them with caution (see table below). Two of the earlier second generation antihistamines, terfenadine (Seldane) and astemizole (Hismanal), were found to have unacceptable heart side effects and are no longer available on the market.

Second Generation Antihistamines
Generic Name Brand Name
lortadine Claritin
fexofenadine Allegra
certirizine (light sedation) Zyrtec
levocetirizine Xyzal
pseudoephedrine/loratadine Claritin-D
pseudoephedrine/fexofenadine Allegra-D
desloratadine Clarinex
azelastine (light sedation) Astelin
olopatadine Patanase

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