Fexofenadine

Structural formula
	( S ) -enantiomer (top) and ( R ) -enantiomer (bottom) ; 1: 1 enantiomer mixture (racemate)
General
Non-proprietary name	Fexofenadine
other names	(±) -2- [4- [1-Hydroxy-4- [4- (hydroxy-diphenyl-methyl) -1-piperidyl] butyl] phenyl] -2-methyl-propionic acid · hydrochloride; ( RS ) -2- [4- [1-Hydroxy-4- [4- (hydroxy-diphenyl-methyl) -1-piperidyl] butyl] phenyl] -2-methyl-propionic acid · hydrochloride; (±) -4- [1-Hydroxy-4- [4- (hydroxydiphenylmethyl) -1-piperidinyl] -butyl] -α, α-dimethylphenylacetic acid · hydrochloride; ( RS ) -4- [1-Hydroxy-4- [4- (hydroxydiphenylmethyl) -1-piperidinyl] -butyl] -α, α-dimethylphenylacetic acid · hydrochloride;
Molecular formula	C 32 H 39 NO 4
External identifiers / databases
EC number	801-893-7
ECHA InfoCard	100.228.648
PubChem	3348
ChemSpider	3231
DrugBank	DB00950
Wikidata	Q415122
Drug information
ATC code	R06 AX26
Drug class	Antihistamine
properties
Molar mass	501.66 g · mol -1
Physical state	firmly
Melting point	195-197 ° C (fexofenadine)
safety instructions
	Please note the exemption from the labeling requirement for drugs, medical devices, cosmetics, food and animal feed
GHS labeling of hazardous substances Fexofenadine hydrochloride	no GHS pictograms
	no GHS pictograms
H and P phrases	H: no H-phrases
	P: no P-phrases
	As far as possible and customary, SI units are used. Unless otherwise noted, the data given apply to standard conditions .

Fexofenadine is a medicinal substance and is used as a third generation antihistamine for hay fever and similar allergic symptoms. Fexofenadine reduces such allergic symptoms by displacing the histamine from the histamine H ₁ receptor .

Clinical effects

Approved areas of application

Fexofenadine is approved to relieve the symptoms of hay fever (seasonal allergic rhinitis) and chronic idiopathic hives , but not in the different strengths that are available on the market, where only one indication is approved per strength.

Side effects

Possible side effects are headache, tiredness, drowsiness, dizziness, nausea, gastrointestinal disorders, menstrual cramps, sore throat, nausea, vomiting, weight gain.

As with other second or third generation H ₁ antihistamines , only a small fraction of the drug crosses the blood-brain barrier . As a hydrophobic substance, fexofenadine can cross the blood-brain barrier, but is transported back into the blood via the multidrug resistance protein 1 , which is why fexofenadine has a comparatively low sedative effect.

Interactions with other substances

In controlled clinical studies, no interactions with other medicinal products that significantly affect the safety or effectiveness of fexofenadine have been observed . Grapefruit juice reduces its effectiveness.

Overdose

Reports of overdose are rare and therefore the symptoms of overdose are poorly understood. The LD ₅₀ in mice was 5000 mg / kg, which is 110 times the recommended adult dose. Studies in humans with a dose of 800 mg once up to 690 mg twice daily for a period of one month showed no significantly adverse clinical effects when compared with a placebo .

chemistry

Stereochemistry

Like many other antihistamines, fexofenadine is used as a racemate . This is important insofar as great importance has been attached to the different pharmacology and pharmacokinetics of enantiomers since the Contergan scandal . In the case of fexofenadine, a study indicates a different stereoselectivity of the P-glycotransport protein compared to the ( R ) - and ( S ) -enatiomers. There are critical voices about the use of racemic drugs.

synthesis

Fexofenadine can be synthesized starting from piperidine-4-carboxylic acid ethyl ester and (4-bromophenyl) acetonitrile.

To obtain the piperidine part, two phenyl groups (Ph) are first introduced on the ester via a Grignard reaction . The amino group is then alkylated with the protected aldehyde 2- (4'-bromobutyl) dioxolane (an acetal ) , the protective group of which is then removed again with acid.

The other part of the fexofenadine molecule is synthesized by double alkylation of the nitrile- derived carbanion with iodomethane . The nitrile group is now hydrolyzed to the carboxylic acid . The aryl bromide is then lithiated with z. B. n -Butyllithium converted to the organolithium compound, which gives fexofenadine together with the aldehyde part after work-up.

Other Information

history

Fexofenadine was initially developed as the successor to Terfenadine and then replaced it in many countries, as Terfenadine was withdrawn from the market there due to serious side effects (exception: Germany ; see also Terfenadine, section " History ").

The older active ingredient terfenadine is oxidized in the body to form the carboxylic acid fexofenadine . This metabolic product has the same biological activity as terfenadine, but causes fewer side effects. Fexofenadine was developed by Hoechst Marion Roussel (now part of Sanofi-Aventis ) and was first approved in the USA in 1996. The patents for the production of fexofenadine and its intermediates are held by the companies Sanofi-Aventis and Albany Molecular Research (AMRI).

Trade names and dosage forms

Fexofenadine is marketed in Germany and Switzerland under the Telfast trademark and under generic trade names. In Austria it is available as Allegra . The tablets contain the hydrochloride salt of the drug. While three different tablet strengths are offered in Germany and Switzerland, only a medium tablet strength is sold in Austria. In some EU member states, fexofenadine is available without a prescription. In the US it is also sold without a prescription under the trade name Allegra . Other trade names: Fastofen, Tilfur, Vifas, Telfexo and Allerfexo.

Individual evidence

^ The Merck Index . An Encyclopaedia of Chemicals, Drugs and Biologicals. 14th edition. 2006, ISBN 0-911910-00-X , p. 693.
↑ Data sheet Fexofenadine hydrochloride from Sigma-Aldrich , accessed on September 22, 2018 ( PDF ).
↑ FE Simons, KJ Simons: Peripheral H1 blockade effect of fexofenadine. In: Ann Allergy Asthma Immunol . 79, 1997, pp. 530-532. PMID 9433369 .
↑ Nicole Schuster: New interaction mechanism discovered. In: Pharmaceutical newspaper . 2008, accessed November 9, 2014 .
↑ T. Tateishi, M. Miura, T. Suzuki, T. Uno: The different effects of itraconazole on the pharmacokinetics of fexofenadine enantiomers. In: Br J Clin Pharmacol . 65, 2008, pp. 693-700. PMID 18294330 .
^ EJ Ariëns: Stereochemistry, a basis for sophisticated nonsense in pharmacokinetics and clinical pharmacology. In: Eur J Clin Pharmacol . 26, 1984, pp. 663-668. PMID 6092093 .
↑ Daniel Lednicer: The Organic Chemistry of Drug Synthesis . tape 6 . Wiley Interscience, New York 1999, ISBN 0-471-24510-0 , pp. 38-40 .

[MerckIndex-1] The Merck Index . An Encyclopaedia of Chemicals, Drugs and Biologicals. 14th edition. 2006, ISBN 0-911910-00-X , p. 693.

[Sigma-2] Data sheet Fexofenadine hydrochloride from Sigma-Aldrich , accessed on September 22, 2018 ( PDF ).

[3] FE Simons, KJ Simons: Peripheral H1 blockade effect of fexofenadine. In: Ann Allergy Asthma Immunol . 79, 1997, pp. 530-532. PMID 9433369 .

[4] Nicole Schuster: New interaction mechanism discovered. In: Pharmaceutical newspaper . 2008, accessed November 9, 2014 .

[5] T. Tateishi, M. Miura, T. Suzuki, T. Uno: The different effects of itraconazole on the pharmacokinetics of fexofenadine enantiomers. In: Br J Clin Pharmacol . 65, 2008, pp. 693-700. PMID 18294330 .

[Ariëns-6] EJ Ariëns: Stereochemistry, a basis for sophisticated nonsense in pharmacokinetics and clinical pharmacology. In: Eur J Clin Pharmacol . 26, 1984, pp. 663-668. PMID 6092093 .

[Lednicer1999-7] Daniel Lednicer: The Organic Chemistry of Drug Synthesis . tape 6 . Wiley Interscience, New York 1999, ISBN 0-471-24510-0 , pp. 38-40 .