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Antihistamines  (Systemic)

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Brand Names

Some commonly used brand names are:

In the U.S.—

  • Alavert13
  • Allegra17
  • Aller-Chlor5
  • AllerMax Caplets10
  • Aller-med10
  • Atarax12
  • Banophen10
  • Banophen Caplets10
  • Benadryl10
  • Benadryl Allergy10
  • Bromphen3
  • Calm X9
  • Chlo-Amine5
  • Chlorate5
  • Chlor-Trimeton5
  • Chlor-Trimeton Allergy5
  • Chlor-Trimeton Repetabs5
  • Clarinex18
  • Claritin13
  • Claritin Reditabs13
  • Compoz10
  • Contac 12 Hour Allergy6
  • Cophene-B3
  • Dexchlor8
  • Dimetapp Allergy Liqui-Gels3
  • Dinate9
  • Diphen Cough10
  • Diphenhist10
  • Diphenhist Captabs10
  • Dormarex 210
  • Dramamine9
  • Dramanate9
  • Genahist10
  • Gen-Allerate5
  • Hydrate9
  • Hyrexin10
  • Hyzine-5012
  • Nasahist B3
  • Nervine Nighttime Sleep-Aid10
  • Nolahist14
  • Nytol QuickCaps10
  • Nytol QuickGels10
  • Optimine1
  • PediaCare Allergy Formula5
  • Periactin7
  • Phenetron5
  • Polaramine8
  • Polaramine Repetabs8
  • Siladryl10
  • Sleep-Eze D10
  • Sleep-Eze D Extra Strength10
  • Sominex10
  • Tavist6
  • Tavist-16
  • Telachlor5
  • Teldrin5
  • Triptone Caplets9
  • Twilite Caplets10
  • Unisom Nighttime Sleep Aid11
  • Unisom SleepGels Maximum Strength10
  • Vistaril12
  • Zyrtec4

In Canada—

  • Aerius18
  • Allegra17
  • Allerdryl10
  • Apo-Dimenhydrinate9
  • Apo-Hydroxyzine12
  • Atarax12
  • Benadryl10
  • Chlor-Tripolon5
  • Claritin13
  • Dimetane3
  • Gravol9
  • Gravol Filmkote9
  • Gravol Filmkote (Junior Strength)9
  • Gravol I/M9
  • Gravol I/V9
  • Gravol L/A9
  • Gravol Liquid9
  • Multipax12
  • Novo-Hydroxyzin12
  • Novo-Pheniram5
  • Optimine1
  • Periactin7
  • PMS-Cyproheptadine7
  • PMS-Dimenhydrinate9
  • Polaramine8
  • Polaramine Repetabs8
  • Reactine4
  • Tavist6
  • Traveltabs9
  • Zyrtec4

Note:

For quick reference, the following antihistamines are numbered to match the corresponding brand names.
This information applies to the following medicines:
1.  Azatadine (a-ZA-ta-deen)
3.  Brompheniramine (brome-fen-EER-a-meen)
4.  Cetirizine (se-TI-ra-zeen)
5.  Chlorpheniramine (klor-fen-EER-a-meen)
6.  Clemastine (KLEM-as-teen)
7.  Cyproheptadine (si-proe-HEP-ta-deen)
8.  Dexchlorpheniramine (dex-klor-fen-EER-a-meen)
9.  Dimenhydrinate (dye-men-HYE-dri-nate)
10.  Diphenhydramine (dye-fen-HYE-dra-meen)
11.  Doxylamine (dox-ILL-a-meen)
12.  Hydroxyzine (hye-DROX-i-zeen)
13.  Loratadine (lor-AT-a-deen)
14.  Phenindamine (fen-IN-da-meen)
17.  Fexofenadine (fex-o-FEN-a-deen)
18.  Desloratadine (des-LOR-at-a-deen)
‡  Generic name product may be available in the U.S.
§  Generic name product may be available in Canada
*  Not commercially available in the U.S.
†  Not commercially available in Canada

Category


Description

Antihistamines are used to relieve or prevent the symptoms of hay fever and other types of allergy. They work by preventing the effects of a substance called histamine, which is produced by the body. Histamine can cause itching, sneezing, runny nose, and watery eyes. Also, in some persons histamine can close up the bronchial tubes (air passages of the lungs) and make breathing difficult.

Some of the antihistamines are also used to prevent motion sickness, nausea, vomiting, and dizziness. In patients with Parkinson's disease, diphenhydramine may be used to decrease stiffness and tremors. Also, the syrup form of diphenhydramine is used to relieve the cough due to colds or hay fever. In addition, since antihistamines may cause drowsiness as a side effect, some of them may be used to help people go to sleep.

Hydroxyzine is used in the treatment of nervous and emotional conditions to help control anxiety. It can also be used to help control anxiety and produce sleep before surgery.

Some antihistamines are used in the treatment of chronic urticaria, which is a persistent hive-like rash.

Antihistamines may also be used for other conditions as determined by your doctor.

Some antihistamine preparations are available only with your doctor's prescription. Others are available without a prescription. However, your doctor may have special instructions on the proper dose of the medicine for your medical condition.

These medicines are available in the following dosage forms:



Before Using This Medicine

In deciding to use a medicine, the risks of taking the medicine must be weighed against the good it will do. This is a decision you and your doctor will make. For antihistamines, the following should be considered:

Allergies—Tell your doctor if you have ever had any unusual or allergic reaction to antihistamines. Also tell your health care professional if you are allergic to any other substances, such as foods, preservatives, or dyes.

Diet—Make certain your health care professional knows if you are on a low-sodium, low-sugar, or any other special diet. Most medicines contain more than their active ingredient, and many liquid medicines contain alcohol.

Pregnancy—Hydroxyzine is not recommended for use in the first months of pregnancy since it has been shown to cause birth defects in animal studies when given in doses many times higher than the usual human dose. Be sure you have discussed this with your doctor.

Desloratadine and fexofenadine have not been studied in pregnant women. However, studies in animals have shown that these medicines cause birth defects or other problems when given in doses higher than the usual human dose. Before taking this medicine, make sure your doctor knows if you are pregnant or if you may become pregnant.

Azatadine, brompheniramine, cetirizine, chlorpheniramine, clemastine, cyproheptadine, dexchlorpheniramine, dimenhydrinate, diphenhydramine, doxylamine, and loratadine have not been studied in pregnant women. However, these medicines have not been shown to cause birth defects or other problems in animal studies.

Breast-feeding—Small amounts of antihistamines pass into the breast milk. Use is not recommended since babies are more susceptible to the side effects of antihistamines, such as unusual excitement or irritability. Also, since these medicines tend to decrease the secretions of the body, it is possible that the flow of breast milk may be reduced in some patients. It is not known yet whether cetirizine, desloratadine, or loratadine cause these same side effects.

Children—Serious side effects, such as convulsions (seizures), are more likely to occur in younger patients and would be of greater risk to infants than to older children or adults. In general, children are more sensitive to the effects of antihistamines. Also, nightmares or unusual excitement, nervousness, restlessness, or irritability may be more likely to occur in children.

Older adults—Elderly patients are usually more sensitive to the effects of antihistamines. Confusion; difficult or painful urination; dizziness; drowsiness; feeling faint; or dryness of mouth, nose, or throat may be more likely to occur in elderly patients. Also, nightmares or unusual excitement, nervousness, restlessness, or irritability may be more likely to occur in elderly patients.

Other medicines—Although certain medicines should not be used together at all, in other cases different medicines may be used together even if an interaction might occur. In these cases, your doctor may want to change the dose, or other precautions may be necessary. When you are taking antihistamines it is especially important that your health care professional knows if you are taking any of the following:

Other medical problems—The presence of other medical problems may affect the use of antihistamines. Make sure you tell your doctor if you have any other medical problems, especially:


Proper Use of This Medicine

Antihistamines are used to relieve or prevent the symptoms of your medical problem. Take them only as directed. Do not take more of them and do not take them more often than recommended on the label, unless otherwise directed by your doctor. To do so may increase the chance of side effects.

Dosing—

The dose of an antihistamine will be different for different patients. Follow your doctor's orders or the directions on the label. The following information includes only the average doses of antihistamines. If your dose is different, do not change it unless your doctor tells you to do so.

The number of capsules or tablets or teaspoonfuls of liquid that you take or the number of suppositories you use depends on the strength of the medicine. Also, the number of doses you take each day and the time between doses depends on whether you are taking a short-acting or long-acting form of antihistamine.

Missed dose—

If you are taking this medicine regularly and you miss a dose, take it as soon as possible. However, if it is almost time for your next dose, skip the missed dose and go back to your regular dosing schedule. Do not double doses.

For patients taking this medicine by mouth:

For patients taking dimenhydrinate or diphenhydramine for motion sickness:

For patients using the suppository form of this medicine:

For patients using the injection form of this medicine :

Storage—

To store this medicine:


Precautions While Using This Medicine

Before you have any skin tests for allergies, tell the doctor in charge that you are taking this medicine. The results of the test may be affected by this medicine.

When taking antihistamines on a regular basis, make sure your doctor knows if you are taking large amounts of aspirin at the same time (as for arthritis or rheumatism). Effects of too much aspirin, such as ringing in the ears, may be covered up by the antihistamine.

Antihistamines will add to the effects of alcohol and other CNS depressants (medicines that slow down the nervous system, possibly causing drowsiness). Some examples of CNS depressants are sedatives, tranquilizers, or sleeping medicine; prescription pain medicine or narcotics; barbiturates; medicine for seizures; muscle relaxants; or anesthetics, including some dental anesthetics. Check with your doctor before taking any of the above while you are using this medicine.

This medicine may cause some people to become drowsy or less alert than they are normally. Even if taken at bedtime, it may cause some people to feel drowsy or less alert on arising. Some antihistamines are more likely to cause drowsiness than others. Drowsiness is less likely with cetirizine, and rare with desloratadine and loratadine. Make sure you know how you react to the antihistamine you are taking before you drive, use machines, or do anything else that could be dangerous if you are not alert.

Antihistamines may cause dryness of the mouth, nose, and throat. Some antihistamines are more likely to cause dryness of the mouth than others . For temporary relief of mouth dryness, use sugarless candy or gum, melt bits of ice in your mouth, or use a saliva substitute. However, if your mouth continues to feel dry for more than 2 weeks, check with your medical doctor or dentist. Continuing dryness of the mouth may increase the chance of dental disease, including tooth decay, gum disease, and fungus infections.

For patients using dimenhydrinate, diphenhydramine, or hydroxyzine:

For patients using diphenhydramine or doxylamine as a sleeping aid:


Side Effects of This Medicine

Along with its needed effects, a medicine may cause some unwanted effects. Although not all of these side effects may occur, if they do occur they may need medical attention.

Check with your doctor immediately if the following side effect occurs:

Also, check with your doctor as soon as possible if any of the following side effects occur:

Other side effects may occur that usually do not need medical attention. These side effects may go away during treatment as your body adjusts to the medicine. However, check with your health care professional if any of the following side effects continue or are bothersome:

Other side effects not listed above may also occur in some patients. If you notice any other effects, check with your health care professional.


Additional Information

Once a medicine has been approved for marketing for a certain use, experience may show that it is also useful for other medical problems. Although this use is not included in product labeling, cetirizine and loratadine are used in certain patients with asthma together with asthma medicines. The antihistamine is used before and during exposure to substances that cause reactions, to prevent or reduce bronchospasm (wheezing or difficulty in breathing).

Cyproheptadine is used as an appetite stimulant, in adults and children

Cyproheptadine is used for treatment of vascular headaches.

Other than the above information, there is no additional information relating to proper use, precautions, or side effects for this use.

Revised: 06/05/2003

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