Antihistamine drugs

Antihistamine drugs are medications that help to relieve symptoms of allergies by blocking the action of histamine, a chemical released by the immune system in response to an allergen. These drugs can help to reduce symptoms such as sneezing, itching, watery eyes, and runny nose. Antihistamines are available in both prescription and over-the-counter forms and can come in various forms such as pills, liquids, nasal sprays, and eye drops. Some common antihistamine drugs include loratadine, cetirizine, diphenhydramine, and fexofenadine. It is important to follow the instructions provided by a healthcare provider or on the medication label when taking antihistamines to ensure safe and effective use.

Antihistamine Drugs

Antihistamines are used to relieve symptoms of allergic reactions, such as:

- Sneezing
- Runny nose
- Itchy, watery eyes
- Hives
- Itching

Mechanism of Action

Antihistamines work by blocking the action of histamine, a chemical released by the body during an allergic reaction. Histamine causes the blood vessels to widen and the release of fluid from the body's tissues, which leads to symptoms such as sneezing, runny nose, and itchy eyes.

Types of Antihistamines

There are two main types of antihistamines:

- First-generation antihistamines: These are older drugs that are effective in relieving allergy symptoms, but they can also cause drowsiness. Examples include diphenhydramine (Benadryl), chlorpheniramine (Chlor-Trimeton), and promethazine (Phenergan).
- Second-generation antihistamines: These are newer drugs that are less likely to cause drowsiness. They are also effective in relieving allergy symptoms. Examples include loratadine (Claritin), cetirizine (Zyrtec), and fexofenadine (Allegra).

Dosage and Administration

Antihistamines are typically taken orally, either as tablets, capsules, or liquid. The dosage and frequency of administration will vary depending on the type of antihistamine and the severity of the allergic reaction.

Side Effects

Common side effects of antihistamines include:

- Drowsiness
- Dry mouth
- Headache
- Nausea
- Blurred vision

Precautions

Antihistamines should be used with caution in people with certain medical conditions, such as liver or kidney disease, or who are taking other medications.

Over-the-Counter (OTC) Antihistamines

Several antihistamines are available over-the-counter for the treatment of mild to moderate allergic reactions. Examples include diphenhydramine (Benadryl), chlorpheniramine (Chlor-Trimeton), loratadine (Claritin), and cetirizine (Zyrtec).

Prescription Antihistamines

Prescription antihistamines are available for the treatment of more severe allergic reactions or when OTC antihistamines are not effective. Examples include fexofenadine (Allegra), levocetirizine (Xyzal), and azelastine (Astelin).