The Use and Misuse of Over the Counter Antihistamines and Decongestants

Health Professional, Medical Reviewer

More than 40 million people suffer from nasal allergy symptoms in the United States. Over-the-counter (OTC) medications for allergy relief fill the shelves of retail pharmacies and there always seem to be new ones coming to the market. Choosing the right medication often depends on matching your symptoms with what the colorful medicine box states the drug inside is capable of relieving. It can be very disappointing when runny nose, sneezing and nasal congestion remain unaffected by the "miracle drug." In desperation, you may decide to double the dose or add another OTC allergy medication. It always boils down to trial and error. But how much error should you risk taking?

All About Antihistamines
Antihistamines are the most common drugs taken to treat nasal allergy symptoms. There are two major classifications of antihistamines:

  • First generation antihistamines have a much higher risk of sedation and fatigue (compared to second generation). These antihistamines often need to be taken three or more times a day to be effective. Members of the first generation include Chlortrimeton, Benadryl, Tavist, Atarax and many others.
  • Second generation antihistamines are very popular because of the lower risk of sedation and fatigue, and they generally need to be taken just once or twice daily.

Since the beginning of this decade, two second generation antihistamines have become available for OTC purchase: loratadine (brand of Claritin, Alavert, Wal-itin and others) and cetirizine (brand of Zyrtec, Walzyr and more coming).

The role of antihistamines and how they work can be reviewed here.

Many prescribed and OTC allergy medications have antihistamine combined with decongestant in order to more broadly cover nasal allergy symptoms. For many years the decongestant component was represented by pseudoephedrine, (Sudafed, the D component of Claritin-D and Zyrtec-D, and many other brands) phenylpropanolamine (previous brands included Entex LA and many OTC allergy medications) and phenylephrine (the decongestant that has replaced pseudoephedrine in many OTC allergy medications currently available). Over the last ten years several allergy medications have disappeared as new ones have arrived.

Why such a makeover in the antihistamine/decongestant line of drugs?
First, the FDA reviewed several decades of data regarding phenylpropanolamine and reported a risk of hemorrhagic stroke (bleeding in the brain) especially in women. This resulted in removal of all forms of this decongestant from retail pharmacies.

Second, pseudoephedrine may be used to make the illegal street drug crystal meth. Currently drug retailers limit the quantities of pseudoephedrine for purchase and store it behind the counter (not available off the shelf). You probably know that purchasing an OTC oral decongestant in major chain drugstores may require two forms of ID and your signature.

Third, the sales of many older (first generation) prescribed and OTC antihistamines and decongestant combinations have plummeted since the newer generation medications have flooded the market (Claritin, Claritin-D, Allegra, Allegra-D, Zyrtec, Zyrtec-D etc.). Many pharmaceutical companies have halted production of their older allergy medications some of which had been available for decades.

Fourth, the FDA removed several allergy and cold relief medications that contain antihistamine or decongestant for children less than 6 years of age because of reported overdoses. There were accounts of some antihistamines causing extreme drowsiness. Oral decongestants were reported to place young children at higher risk of tachycardia (racing of the heart), palpitations, insomnia, irritability and tremor (and this is not a complete list). It was concluded that young children may be more vulnerable to the potential side effects of OTC allergy drugs. Errors in dosing and in some cases intentional dosing above recommended guidelines resulted in serious injury.

OTC allergy medications may be effective and safely used when dosage guidelines are followed. Over dosing should be strictly avoided. This means you should read the package insert or written dosage guidelines carefully. Maximum allowed doses vary based on age, other medications being taken at the same time and health status of your liver and kidneys.

Although newer antihistamines have a lower risk of drowsiness, doses taken above the recommended levels may cause not only drowsiness but other serious side effects. If you have questions or are uncertain about how a medication should be taken talk to your doctor or pharmacist.

Are you happy about previously prescribed allergy medication going OTC?

See also:

How to choose the best allergy medicine