Antihistamines block histamine release from histamine-1 receptors and are mostly used to treat allergies or cold and flu symptoms, although some first-generation antihistamines (also called sedating antihistamines) may be used for other conditions, such as nausea or motion sickness.
Histamine-1 receptors are located in your airways (breathing tubes), blood vessels, stomach, and esophagus (throat area). Allergens, such as pollen or pet fur can stimulate these receptors, causing the release of histamine, which results in symptoms such as a rash, sneezing, a runny nose, or a narrowing of the airways (also called bronchoconstriction). Histamine-1 receptors are also found in the brain and spinal cord and first-generation antihistamines (sedating antihistamines) can cross through the blood/brain barrier into the brain and act on these receptors, causing sleepiness (sedation), and drowsiness.
Antihistamines can help relieve the symptoms of an allergic reaction, such as:
This makes antihistamines very effective for the treatment of:
Sedating antihistamines (see explanation below) also act in the brain and spinal cord, and on other receptors. This makes some of them also useful for:
Antihistamines can be classified into two main categories:
First-generation (sedating) antihistamines were developed more than seventy years ago and are still in widespread use today. They act on histamine receptors in the brain and spinal cord and in the rest of the body (called the periphery). They also act on muscarinic, alpha-adrenergic, and serotonin receptors. This means that first-generation antihistamines are more likely to cause side effects such as sedation, dry mouth, dizziness, low blood pressure, and a rapid heart-beat. They are also more likely than second-generation antihistamines to impair a person’s ability to drive or operate machinery. Interactions with other drugs are more common with first-generation antihistamines compared with second-generation antihistamines.
Second generation (non-sedating) antihistamines were developed in the 1980s and are much less sedating than first-generation antihistamines. They act on histamine-1 receptors in the periphery and are unlikely to penetrate the brain, so are less likely to cause side effects or interact with drugs. Most second-generation antihistamines do not cause drowsiness, although some (such as cetirizine and fexofenadine), may be more likely to do so at higher dosages.
| Generic name | Brand name examples | Duration of action |
|---|---|---|
| brompheniramine | Generic | 12h |
| carbinoxamine maleate | Generic | 12h |
| chlorpheniramine | Aller-Chlor | 24h |
| clemastine | Generic | 12h |
| diphenhydramine | Benadryl | 12h |
| hydroxyzine | Vistaril | 24h |
| triprolidine | Discontinued | 12h |
| Generic name | Brand name | Duration of action |
|---|---|---|
| azelastine nasal spray | Astelin | 12h |
| cetirizine | Zyrtec Allergy, Children’s Zyrtec | 24h+ |
| desloratadine | Clarinex, Clarinex Reditabs | 24h+ |
| fexofenadine | Allegra Allergy, Children's Allegra Allergy | 12-24h |
| levocetirizine | Xyzal | 24h+ |
| loratadine | Alavert, Claritin | 24h |
| olopatadine nasal spray | Patanase | 12h |
Side effects of first-generation (sedating) antihistamines may include:
Side effects of second-generation (non-sedating) antihistamines may include:
Data Source:drugs.com
BENZTROPINE MES is a medication that is commonly used to treat symptoms of Parkinson's disease and certain movement disorders. It works by blocking the action of a specific neurotransmitter in the brain, which helps to reduce muscle stiffness and tremors. This medication is available in tablet form and is typically taken orally. It is important to follow the prescribed dosage and instructions provided by a healthcare professional when taking BENZTROPINE MES.
Data Source:medlineplus.gov
BONJESTA ER is a medication that is used to treat nausea and vomiting during pregnancy. It is an extended-release tablet that provides long-lasting relief from these symptoms. BONJESTA ER works by blocking certain chemicals in the brain that trigger nausea and vomiting. It is a safe and effective option for pregnant women who are experiencing morning sickness.
Data Source:medlineplus.gov
DICLEGIS DR is a medication that is commonly prescribed to treat morning sickness in pregnant women. It is a delayed-release tablet that contains a combination of doxylamine succinate and pyridoxine hydrochloride. This medication helps to alleviate nausea and vomiting associated with pregnancy, allowing women to have a more comfortable experience during their first trimester. DICLEGIS DR is typically taken once daily before bedtime, and it is important to follow the dosage instructions provided by a healthcare professional.
Data Source:medlineplus.gov
Doxyamine-Pyridoxine is a combination medication used to treat nausea and vomiting during pregnancy. It contains doxylamine, an antihistamine, and pyridoxine, a form of vitamin B6. This medication works by blocking certain chemicals in the body that cause nausea and vomiting. It is commonly prescribed to pregnant women who experience morning sickness.
Data Source:medlineplus.gov
Hydroxyzine Pam is a medication that is commonly used to treat anxiety and tension. It belongs to a class of drugs known as antihistamines, which work by blocking certain natural substances in the body that cause allergic reactions. Hydroxyzine Pam is available in tablet form and is typically taken orally. It is known to have a calming effect on the central nervous system, helping to reduce anxiety and promote relaxation. This medication is often prescribed by healthcare professionals to help manage symptoms of anxiety disorders, such as generalized anxiety disorder and panic disorder. It may also be used as a sedative before and after surgical procedures. Hydroxyzine Pam is generally well-tolerated, but like any medication, it may cause side effects in some individuals. Common side effects may include drowsiness, dry mouth, and blurred vision. It is important to follow the prescribed dosage and consult with a healthcare professional before starting or stopping this medication.
Data Source:medlineplus.gov
Hydroxyzine HCL is a medication commonly used to treat anxiety and tension. It belongs to a class of drugs called antihistamines, which work by blocking certain natural substances in the body that cause allergic reactions. Hydroxyzine HCL can also be used as a sedative to help relax and calm individuals before surgery or medical procedures. It is available in tablet, capsule, and liquid form and is typically taken orally. The dosage and duration of treatment may vary depending on the individual's condition and response to the medication. It is important to follow the instructions provided by a healthcare professional and to inform them of any other medications or medical conditions before starting hydroxyzine HCL.
Data Source:medlineplus.gov
