- Information
- AI Chat
Was this document helpful?
Antihistamines
Course: Secondary education (EDU 329)
18 Documents
Students shared 18 documents in this course
Was this document helpful?
Q.No.1 Classify antihistamines on the basis of their receptor sites.
Ans: Antihistamines on the basis of their receptor sites:
Antihistamines are drugs that antagonize these effects by blocking or inhibiting histamine
receptors (H receptors), and they are categorized as either H1 or H2 according to the type of H
receptor targeted.
H1-receptor blockers:
The H1-receptor blockers can be divided into first- and second generation drug. The older first-
generation drugs are still widely used because they are effective and inexpensive. However, most
of these drugs penetrate the CNS and cause sedation. Furthermore, they tend to interact with
other receptors, producing a variety of unwanted adverse effects. In contrast, the second-
generation agents are specific for peripheral H1receptors. Because they are made polar mainly by
adding carboxyl groups (for example, cetirizineis the carboxylated derivative of hydroxyzine),
the second-generation agents do not penetrate the blood–brain barrier, causing less CNS
depression than the firstgeneration drugs. Among the second-generation agents, desloratadine,
fexofenadin, and show the least sedation. Cetirizine and levocetirizine are partially sedating
second-generation agents.
H2-receptor blockers:
H2-receptor blockers block the actions of histamine at all H2-receptors, their chief clinical use is
as inhibitors of gastric acid secretion in the treatment of ulcers and heartburn. H2-receptor
blockers include cimetidine, ranitidine, famotidine,and nizatidine.
Q.No.2 Discuss non-sedative histamines in detail.
Ans: Non-Sedative Histamines:
Second and third generation antihistamines are non-sedating or minimally sedating and cause
less drowsiness than the first generation drugs. This is because they have limited penetration into
the brain. They also have fewer side effects because they only bind to the selected receptors.
Some of which include Citrazine, Loratidine, Astemizole, Azelastin.
Citrazine:
Cetirizine is second generation non-sedative antihistamine that reduces or blocks the natural
chemical histamine in the body. It is used to treat cold or allergy symptoms such as sneezing, itching,
watery eyes, or runny nose.
Astemizole:
