Dr. Glaser's "Chemistry is in the News"
To Accompany Bruice, Organic Chemistry, 3/e.
Chapter 30.
The Organic Chemistry of Drugs: Discovery and Design.
Editorial Comments
Allergies are a real problem and allergy relief is a big business!
I am writing this in Missouri and I know
what it is like! There are more people in Missouri suffering from
allergies than in any other state - and I am one of them. Find out what
allergies are by taking a look at the
Claritin site, a
commercial site, and, if you prefer, you can also get some helpful information
about prescription antihistamines
from the American Academy of Family Physicians.
Antihistamines to the rescue! There are two types of antihistamines. Most antihistamines that require prescription are so-called "non-sedating" antihistamines, that is, they won't make you sleepy. The older "over-the-counter" antihistamines have the undesirable side effect of causing drowsiness. Obviously, the non-sedating antihistamines are superior as they allow people to pursue their normal lives.
Benadryl is the sedating antihistamine diphenylhydramine which is contained in the Visualization Center Accompanying Chapter 30. The use of sedating antihistamine is accompanied by drowsiness, dizziness, dryness of mouth, nausea and nervousness may occur. Claritin is the non-sedating antihistamine loratadine. Allegra is another popular non-sedating antihistamine. Allegra is fexofenadine which is converted in the body into the active and also non-sedating antihistamine terfenadine.
How do antihistamines work? Antihistamines typically are antagonists of the H1 class of histamine receptors. A review on histamine receptors is available online. Allergens cause an excess of histamine in the body and thereby lead to symptoms of the common cold. Histamine is an ammonium cation that contains an imidazole ring; a molecular model of the histamine ion is contained in the visualization center. This cation is bound by the negatively charged histamine receptor. So, the trick is to make a molecule that is bound by the histamine receptor but that does not trigger the same response of the receptor. Many of these drugs also contain the ammonium ion part but differ in the side chain (usually more bulky) and benadryl does just that.Questions
Question 1:
In your own words, describe the effects of excess histamine in the body.
Answer 1:
Bruice, 3/e, Chapter 30.
Question 2:
Describe, in your own words, the desired properties of
"antihistamines".
Answer 2:
Bruice, 3/e, Chapter 30.
Question 3:
Provide one example of a sedating antihistamine. Provide the name
and the structure of the sedating antihistamine.
Answer 3:
Bruice, 3/e, Chapter 30.
Question 4:
Provide one example of a non-sedating antihistamine. Provide the
name and the structure of the non-sedating antihistamine.
Answer 4:
Bruice, 3/e, Chapter 30.