What are antihistamines?

Medicines are very important supplies in modern life. The function of medicines is to treat diseases and restore the body to health. There are many types of diseases, and people make adaptive medicines based on the characteristics of the diseases. For example, antihistamines are commonly used drugs for mental illnesses, and they have a good therapeutic inhibitory effect on such diseases. Let’s take a look at what antihistamines are there.

Antihistamine anti-allergic drugs are divided into first-generation antihistamines, second-generation antihistamines and third-generation antihistamines. Currently, first-generation antihistamines represented by diphenhydramine, chlorpheniramine and promethazine are gradually being replaced by second-generation antihistamines with no sedative effect or mild sedative effect due to their strong central nervous system inhibitory effects. The use of some second-generation antihistamines has been gradually reduced due to the discovery of obvious cardiac toxicity (such as terfenadine, astemizole, etc.), and third-generation antihistamines such as fexofenadine and levocetirizine have been introduced.

Fexofenadine

Initial studies found that terfenadine not only has pharmacological effects itself, but its metabolites also have pharmacological activity. For example, if it is used directly to treat allergic reactions, it can be free from drug enzyme metabolism and eliminate cardiac toxicity to the human body. It is based on this characteristic of terfenadine that in 1995, the German Hoechst Marion Roussel Pharmaceutical Factory first researched and developed the active metabolite of terfenadine - fexofenadine, which was approved by the FDA in 1997. Because the drug has no cardiac toxic side effects, it is considered by some scholars to be a third-generation antihistamine drug with the characteristics of high efficiency, long-acting and low toxicity.

Levocetirizine

Levorotatory cetirizine was launched in February 2001. It is a third-generation antihistamine and a single optical isomer of the second-generation antihistamine cetirizine. It is mainly used to treat allergic diseases of the respiratory system, skin and eyes, such as allergic rhinocorticitis, allergic skin diseases, allergic asthma, etc. It has the advantages of rapid onset of action, strong and lasting effect and few side effects.

Desloratadine

Desloratadine has completed Phase III clinical trials in the United States, and Schering-Plough has submitted a new drug application to the FDA. It has not yet been approved for marketing, but it was approved for marketing by the European Union EMEA in January 2001. It has also been approved for marketing in my country for the treatment of seasonal allergic rhinitis and chronic urticaria in adults and children over 12 years old. It can also be used as an adjuvant treatment for asthma.