Title: Fexofenadine
CAS Registry Number: 83799-24-0
CAS Name: a,a-Dimethyl-4-[1-hydroxy-4-[4-(hydroxydiphenylmethyl)-1-piperidinyl]butyl]benzeneacetic acid
Additional Names: carboxyterfenadine; terfenadine carboxylate
Manufacturers' Codes: MDL-16455
Molecular Formula: C32H39NO4
Molecular Weight: 501.66
Percent Composition: C 76.61%, H 7.84%, N 2.79%, O 12.76%
Literature References: Nonsedating-type histamine H1-receptor antagonist. Prepn: A.A. Carr et al., DE 3007498; eidem, US 4254129 (1980, 1981 both to Richardson-Merrell). Identification as active metabolite of terfenadine, q.v.: D. A. Garteiz et al., Arzneim.-Forsch. 32, 1185 (1982). Synthesis: S. H. Kawai et al., J. Org. Chem. 59, 2620 (1994). HPLC separation from terfenadine: K. Y. Chan et al., J. Chromatogr. 571, 291 (1991); determn in biological fluids: A. Terhechte, G. Blaschke, ibid. A 694, 219 (1995). Effects on cardiac K+ channels: D. Rampe et al., Mol. Pharmacol. 44, 1240 (1993). Comparative analysis of cardiotoxic potential: J. A. Hey et al., Arzneim.-Forsch. 46, 153 (1996). Clinical pharmacology in children: F. E. R. Simons et al., J. Allergy Clin. Immunol. 98, 1062 (1996).
Properties: Crystals from methanol-butanone, mp 195-197° (Carr); also reported as white crystals from methanol, mp 142-143° (Kawai).
Melting point: mp 195-197° (Carr); mp 142-143° (Kawai)
Derivative Type: Hydrochloride
CAS Registry Number: 153439-40-8
Trademarks: Allegra (Aventis); Telfast (Aventis)
Molecular Formula: C32H39NO4.HCl
Molecular Weight: 538.12
Percent Composition: C 71.42%, H 7.49%, N 2.60%, O 11.89%, Cl 6.59%
Therap-Cat: Antihistaminic.
Keywords: Antihistaminic.
F-Gitonin Fialuridine Fibrin Fibroblast Growth Factor Fibrolase

Systematic (IUPAC) name
(RS)- 2-[4-[1-Hydroxy- 4-[4-(hydroxy- diphenyl- methyl) - 1-piperidyl]butyl]phenyl]- 2-methyl- propanoic acid
Clinical data
Trade names Allegra,Axodin
AHFS/Drugs.com monograph
MedlinePlus a697035
Licence data US FDA:link
Pregnancy cat. B2 (AU) C (US)
Legal status Unscheduled (AU) OTC (CA) POM (UK) OTC (US)
Routes Oral
Pharmacokinetic data
Bioavailability 30-41%[1]
Protein binding 60-70%
Metabolism Hepatic (5% of dose)
Half-life 14.4 hours
Excretion Feces (~80%) and urine (~11%) as unchanged drug
CAS number 83799-24-0 YesY
ATC code R06AX26
PubChem CID 3348
DrugBank DB00950
ChemSpider 3231 YesY
KEGG D07958 YesY
Chemical data
Formula C32H39NO4 
Mol. mass 501.656
 YesY (what is this?)  (verify)

Fexofenadine (trade names Allegra, Fexidine, Telfast, Fastofen, Tilfur, Vifas, Telfexo, Allerfexo) is an antihistamine pharmaceutical drug used in the treatment of hay fever, allergy symptoms, and urticaria.[2]

It was developed as a successor of and alternative to terfenadine (trade names include Triludan and Seldane), an antihistamine that caused QT interval prolongation, potentially leading to cardiac arrhythmia. Fexofenadine, like other second- and third-generation antihistamines, does not readily cross the blood–brain barrier, and so causes less drowsiness than first-generation histamine-receptor antagonists. It works by being an antagonist to the H1 receptor.[3]

It has been variously described as either a second-generation[4] or a third-generation antihistamine.[5]