Cetirizine
Cetirizine is a second-generation antihistamine used to treat allergic rhinitis (hay fever), dermatitis, and urticaria (hives).[6] Common side effects include sleepiness, dry mouth, headache, and abdominal pain.[16] Cetirizine is also commonly prescribed to treat acute and (in particular cases) chronic urticaria (hives), more efficiently than any other second-generation antihistamine.In the UK, up to 30 tablets of 10 mg are on the general sales list (of pharmaceuticals) and can be purchased without a prescription and pharmacist supervision.Their report noted that some patients indicated the itchiness impacted their ability to work, sleep or perform normal daily activities.[27] Cetirizine crosses the blood–brain barrier only slightly, and for this reason, produces minimal sedation compared to many other antihistamines.[3][2][39] Similar findings were reported for levocetirizine, which had its Tmax delayed by 1.25 hours and its Cmax decreased by about 36% when administered with a high-fat meal.[1] The drug is bound to albumin with high affinity, while α1-acid glycoprotein and lipoproteins contribute much less to total plasma protein binding.[3][1] Cetirizine poorly and slowly crosses the blood–brain barrier, which is thought to be due to its chemical properties and its activity as a P-glycoprotein substrate.[43] Because of this, it does not interact significantly with drugs that inhibit or induce cytochrome P450 enzymes such as theophylline, erythromycin, clarithromycin, cimetidine, or alcohol.[44] The 1-(4-chlorophenylmethyl)-piperazine is alkylated with methyl (2-chloroethoxy)-acetate in the presence of sodium carbonate and xylene solvent to produce the Sn2 substitution product in 28% yield.[50][51] Cetirizine is marketed under the brand names Alatrol, Alerid, Allacan, Allercet, Alzene, Cerchio, Cetirin, Cetizin, Cetriz, Cetzine, Cezin, Cetgel, Cirrus, Histec, Histazine, Humex, Letizen, Okacet (Cipla), Piriteze, Reactine, Razene, Rigix, Sensahist (Oethmann, South Africa), Triz, Zetop, Zirtec, Zirtek, Zodac, Zyllergy, Zynor, Zyrlek, and Zyrtec (Johnson & Johnson), inter alios.
Drugs.comMedlinePlusLicense dataDailyMedPregnancycategoryRoutes ofadministrationBy mouthATC codeR06AE07S01GX12Legal statusGeneral sales listPharmacokineticBioavailabilityProtein bindingMetabolismcytochrome P450Onset of actionElimination half-lifeExcretionIUPAC nameCAS NumberIUPHAR/BPSDrugBankChemSpiderChEMBLCompTox DashboardECHA InfoCardFormulaMolar massSMILESsecond-generation antihistamineallergic rhinitisdermatitisurticariadiphenhydraminefirst-generation antihistaminefirst-generation antihistaminesH1 receptorfexofenadineloratadinepregnancybreastfeedinghistaminesomnolenceWorld Health Organization's List of Essential Medicinesgeneric medicationhay fevertabletsheadachedry mouthdrowsinessfatiguetachycardiaitchinesslevocetirizineselectiveantagonistlevorotatoryenantiomerselectivitymuscarinic acetylcholineserotonindopamineα-adrenergic receptorsanticholinergiccardiotoxicityblood–brain barrierpositron emission tomographyhydroxyzinesedativeNF-κBcytokineschemokineseosinophilchemotaxisVCAM-1atopic dermatitisabsorbedoral administrationpharmacokineticsSteady-state levelsplasma protein bindingalbuminaffinityα1-acid glycoproteinlipoproteinsvolume of distributionP-glycoproteinsubstrateinhibitinducetheophyllineerythromycinclarithromycincimetidinealcoholmetabolic pathwaysoxidationconjugationtransformationeliminatedactive transporthepatic impairmentrenal impairmentduration of actionstereoisomersdiphenylmethylpiperazineAnaloguescyclizinecombination medicationpseudoephedrinedecongestantZyrtec-DJohnson & JohnsonWorld Health OrganizationAntihistaminesBenzimidazolesAstemizoleAzelastineBilastineEmedastineMizolastineTalastineDiarylmethanesBromazine (bromodiphenhydramine)