# Structural Biochemistry/Allegra
## Overview

Allegra has generic name Fexofenadine and is classified as a Histamine H1-receptor antagonist. It is manufactured by Advancis Pharmaceutical Corporation and has chemical name (±)-4-[1 hydroxy-4-[4-(hydroxydiphenylmethyl)-1-piperidinyl]-butyl]-, -dimethyl benzeneacetic acid hydrochloride. One of the main uses is to treat symptoms caused by allergies. Fexofenadine hydrochloride is 60% to 70% bound to plasma protein, primarily albumin and 1-acid glycoprotein. Approximately 5% of the total dose of fexofenadine hydrochloride is eliminated by hepatic metabolism through metabolite terfenadine. The half-life is 14.4 hours for 60 mg. The drugs works by competitively inhibiting the H-1 receptor site and preventing histamine-1 from attaching the receptor sites to cause allergy symptoms. Histamine-1 is released by mast cells in the presence of certain stimulus that the body is allergic to. The drug does not prevent the release of histamine-1 by the mast cells but rather competes with the histamine-1 substrates for positions at the receptor sites.

## Why prescribe this?

Fexofenadine is prescribe to relieve allergy symptoms of seasonal allergic rhinitis such as hay fever. Some allergy symptoms in children over 2 years old and adults include runny nose; sneezing; red, itchy, or watery eyes; or itching of the nose, throat, or roof of the mouth. It is also used to relieve symptoms of urticaria such as red, itchy raised areas of the skin, including itching and rash in children 6 months and over and adults. In all, Fexofenadine is in a class of medications called antihistamines. Antihistamines blocks the effects of histamine, a substance in the body that cause allergy to happen. Fexofenadine is known only for controlling the symptoms of seasonal allergic rhinitis and urticaria but it is not a cure for these conditions.

## How should this medication be used?

Fexofenadine comes as a tablet or liquid to take by mouth. People who are taking this medication normally take it with water once or twice a day depending on how bad their allergy symptom is. Do not take any kind of fruit juices, such as orange, grapefruit, or apple juice because the performance of fexofenadine in the body system will not be as effective. Remember to take this medication at around the same time(s) every day. Carefully read what the prescription label states and follow it accordingly. Do not take more or less of it or take it more often than prescribed by the doctor. If fexofenadine is use in liquid form, it is crucial to shake the bottle well before use.

## Side Effects

Taking fexofenadine may cause certain side effects. When any of these side effects listed below are severe and do not go away it is important to quickly consult with the doctor.
* headache
* dizziness
* diarrhea
* vomiting
* pain in the arms, legs, or back
* pain during menstrual period
* cough
Note: Serious side effects and should call doctor immediately are hives, rash, itching, difficulty breathing or swallowing, and swelling in face area or lips.

## Synthesis

Fexofenadine may be synthesized as shown from piperidine-4-carboxylate ester and 4-bromophenylacetonitrile.

## References

http://www.ncbi.nlm.nih.gov/pubmedhealth/PMH0001008/
* ↑ Daniel Lednicer (1999). The Organic Chemistry of Drug Synthesis. Vol. 6. New York: Wiley Interscience. ISBN 0-471-24510-0.
* ↑ Kawai, SH; Hambalek, RJ; Just, G (1994). "A facile synthesis of an oxidation product of terfenadine". J. Org. Chem. 59 (9): 2620–22. doi:10.1021/jo00088a056. {{cite journal}}: Unknown parameter |month= ignored (help)
http://www.medicinenet.com/fexofenadine-oral/article.html
http://www.rxlist.com
https://online.epocrates.com