The metabolism of Levocetirizine can be decreased when combined with Fluconazole. The risk or severity of adverse effects can be increased when Tetrabenazine is combined with Levocetirizine. The risk or severity of adverse effects can be increased when Pipamperone is combined with Levocetirizine. The risk or severity of adverse effects can be increased when Etifoxine is combined with Levocetirizine. Levocetirizine may increase the central nervous system depressant (CNS depressant) activities of Paraldehyde. The risk or severity of adverse effects can be increased when Fencamfamine is combined with Levocetirizine. The risk or severity of adverse effects can be increased when Efavirenz is combined with Levocetirizine. The risk or severity of adverse effects can be increased when Fluphenazine is combined with Levocetirizine. The risk or severity of adverse effects can be increased when Sepranolone is combined with Levocetirizine. The risk or severity of adverse effects can be increased when Levocetirizine is combined with Brexpiprazole. The risk or severity of adverse effects can be increased when Levocetirizine is combined with Dapoxetine. The risk or severity of adverse effects can be increased when Flunitrazepam is combined with Levocetirizine. The serum concentration of Levocetirizine can be decreased when it is combined with Enzalutamide. The risk or severity of adverse effects can be increased when Levocetirizine is combined with Indalpine. The risk or severity of adverse effects can be increased when Iloperidone is combined with Levocetirizine. The risk or severity of adverse effects can be increased when Hexobarbital is combined with Levocetirizine. The risk or severity of adverse effects can be increased when Clorazepate is combined with Levocetirizine. The risk or severity of adverse effects can be increased when Canertinib is combined with Levocetirizine. The risk or severity of adverse effects can be increased when Levocetirizine is combined with Tasimelteon. Levocetirizine may increase the central nervous system depressant (CNS depressant) activities of Buprenorphine. The serum concentration of Levocetirizine can be increased when it is combined with Simeprevir. The metabolism of Levocetirizine can be increased when combined with Carbamazepine. The risk or severity of adverse effects can be increased when Paliperidone is combined with Levocetirizine. The risk or severity of adverse effects can be increased when Protriptyline is combined with Levocetirizine. The risk or severity of adverse effects can be increased when Levocetirizine is combined with Sertraline. The risk or severity of adverse effects can be increased when Allopregnanolone is combined with Levocetirizine. The risk or severity of adverse effects can be increased when Fentanyl is combined with Levocetirizine. Phentermine may decrease the sedative activities of Levocetirizine. The risk or severity of adverse effects can be increased when Levomethadyl Acetate is combined with Levocetirizine. The risk or severity of adverse effects can be increased when Lithium is combined with Levocetirizine. The risk or severity of adverse effects can be increased when Quazepam is combined with Levocetirizine. The risk or severity of adverse effects can be increased when Zopiclone is combined with Levocetirizine. The risk or severity of adverse effects can be increased when Carbinoxamine is combined with Levocetirizine. The serum concentration of Levocetirizine can be decreased when it is combined with Vemurafenib. The risk or severity of adverse effects can be increased when Olopatadine is combined with Levocetirizine. The risk or severity of adverse effects can be increased when Meclizine is combined with Levocetirizine. Sodium oxybate may increase the central nervous system depressant (CNS depressant) activities of Levocetirizine. The risk or severity of adverse effects can be increased when Meprobamate is combined with Levocetirizine. The risk or severity of adverse effects can be increased when Morphine is combined with Levocetirizine. The risk or severity of adverse effects can be increased when Quetiapine is combined with Levocetirizine. The risk or severity of adverse effects can be increased when Etorphine is combined with Levocetirizine. The risk or severity of adverse effects can be increased when Reserpine is combined with Levocetirizine. Levocetirizine may increase the central nervous system depressant (CNS depressant) activities of Methotrimeprazine. The risk or severity of adverse effects can be increased when Levocetirizine is combined with Duloxetine. The risk or severity of adverse effects can be increased when Estazolam is combined with Levocetirizine. The risk or severity of adverse effects can be increased when Zotepine is combined with Levocetirizine. The risk or severity of adverse effects can be increased when Chloroprocaine is combined with Levocetirizine. The risk or severity of adverse effects can be increased when Methylecgonine is combined with Levocetirizine. The risk or severity of adverse effects can be increased when Dexmedetomidine is combined with Levocetirizine. The risk or severity of adverse effects can be increased when Hydromorphone is combined with Levocetirizine. The risk or severity of adverse effects can be increased when Benzyl alcohol is combined with Levocetirizine. The metabolism of Levocetirizine can be decreased when combined with Itraconazole. The risk or severity of adverse effects can be increased when Trans-2-Phenylcyclopropylamine is combined with Levocetirizine. The serum concentration of Levocetirizine can be increased when it is combined with Fosaprepitant. The risk or severity of adverse effects can be increased when Levocetirizine is combined with Alaproclate. The metabolism of Levocetirizine can be increased when combined with Phenobarbital. The risk or severity of adverse effects can be increased when Levocetirizine is combined with Ziconotide. The serum concentration of Levocetirizine can be decreased when it is combined with Tocilizumab. The metabolism of Levocetirizine can be decreased when combined with Idelalisib. The risk or severity of adverse effects can be increased when Halazepam is combined with Levocetirizine. The metabolism of Levocetirizine can be decreased when combined with Crizotinib. The metabolism of Levocetirizine can be decreased when combined with Ziprasidone. The risk or severity of adverse effects can be increased when Heroin is combined with Levocetirizine. The metabolism of Levocetirizine can be increased when combined with Fosphenytoin. The risk or severity of adverse effects can be increased when Dexbrompheniramine is combined with Levocetirizine. The risk or severity of adverse effects can be increased when Ketamine is combined with Levocetirizine. The risk or severity of adverse effects can be increased when Ethotoin is combined with Levocetirizine. The serum concentration of Levocetirizine can be decreased when it is combined with Deferasirox. Levocetirizine may decrease effectiveness of Benzylpenicilloyl Polylysine as a diagnostic agent. 3,4-Methylenedioxyamphetamine may decrease the sedative activities of Levocetirizine. The risk or severity of adverse effects can be increased when Ethylmorphine is combined with Levocetirizine. Ritobegron may decrease the sedative activities of Levocetirizine. The risk or severity of adverse effects can be increased when Melatonin is combined with Levocetirizine. The risk or severity of adverse effects can be increased when Tandospirone is combined with Levocetirizine. The risk or severity of adverse effects can be increased when Pentazocine is combined with Levocetirizine. The serum concentration of Levocetirizine can be decreased when it is combined with Bosentan. The risk or severity of adverse effects can be increased when Nortriptyline is combined with Levocetirizine. The risk or severity of adverse effects can be increased when Dextromoramide is combined with Levocetirizine. The risk or severity of adverse effects can be increased when Eltanolone is combined with Levocetirizine. Levocetirizine may increase the central nervous system depressant (CNS depressant) activities of Azelastine. The risk or severity of adverse effects can be increased when Tiapride is combined with Levocetirizine. The risk or severity of adverse effects can be increased when Flibanserin is combined with Levocetirizine. Levocetirizine may increase the central nervous system depressant (CNS depressant) activities of Mirtazapine. The risk or severity of adverse effects can be increased when Oxybuprocaine is combined with Levocetirizine. The serum concentration of Levocetirizine can be increased when it is combined with Stiripentol. The risk or severity of adverse effects can be increased when Desloratadine is combined with Levocetirizine. The serum concentration of Levocetirizine can be decreased when it is combined with St. John's Wort. The risk or severity of adverse effects can be increased when Clozapine is combined with Levocetirizine. The risk or severity of adverse effects can be increased when Methsuximide is combined with Levocetirizine. The risk or severity of adverse effects can be increased when Triazolam is combined with Levocetirizine. The metabolism of Levocetirizine can be increased when combined with Pentobarbital. The risk or severity of adverse effects can be increased when Methaqualone is combined with Levocetirizine. The risk or severity of adverse effects can be increased when Triflupromazine is combined with Levocetirizine. The metabolism of Levocetirizine can be decreased when combined with Clarithromycin. The risk or severity of adverse effects can be increased when Tramadol is combined with Levocetirizine. The metabolism of Levocetirizine can be decreased when combined with Cyclosporine. The risk or severity of adverse effects can be increased when Proparacaine is combined with Levocetirizine. The metabolism of Levocetirizine can be decreased when combined with Isradipine. Minocycline may increase the central nervous system depressant (CNS depressant) activities of Levocetirizine. Diethylpropion may decrease the sedative activities of Levocetirizine. The risk or severity of adverse effects can be increased when Oxymorphone is combined with Levocetirizine. Mephentermine may decrease the sedative activities of Levocetirizine. The risk or severity of adverse effects can be increased when Benzocaine is combined with Levocetirizine. Levocetirizine may increase the central nervous system depressant (CNS depressant) activities of Thalidomide. The risk or severity of adverse effects can be increased when Fospropofol is combined with Levocetirizine. The risk or severity of adverse effects can be increased when Bupivacaine is combined with Levocetirizine. The metabolism of Levocetirizine can be decreased when combined with Erythromycin. The risk or severity of adverse effects can be increased when Tolcapone is combined with Levocetirizine. Hydroxyzine may increase the central nervous system depressant (CNS depressant) activities of Levocetirizine. The risk or severity of adverse effects can be increased when Tetracaine is combined with Levocetirizine. The risk or severity of adverse effects can be increased when Tiagabine is combined with Levocetirizine. The risk or severity of adverse effects can be increased when Maprotiline is combined with Levocetirizine. The metabolism of Levocetirizine can be decreased when combined with Cobicistat. The risk or severity of adverse effects can be increased when Opium is combined with Levocetirizine. The risk or severity of adverse effects can be increased when Ethyl carbamate is combined with Levocetirizine. Dextroamphetamine may decrease the sedative activities of Levocetirizine. The risk or severity of adverse effects can be increased when Flunarizine is combined with Levocetirizine. The risk or severity of adverse effects can be increased when Clomipramine is combined with Levocetirizine. The risk or severity of adverse effects can be increased when Levocetirizine is combined with Gabapentin Enacarbil. The metabolism of Levocetirizine can be decreased when combined with Telithromycin. The risk or severity of adverse effects can be increased when Carisoprodol is combined with Levocetirizine. Midomafetamine may decrease the sedative activities of Levocetirizine. The risk or severity of adverse effects can be increased when Zaleplon is combined with Levocetirizine. Brimonidine may increase the central nervous system depressant (CNS depressant) activities of Levocetirizine. The risk or severity of adverse effects can be increased when Amisulpride is combined with Levocetirizine. The risk or severity of adverse effects can be increased when Pipotiazine is combined with Levocetirizine. The risk or severity of adverse effects can be increased when Benperidol is combined with Levocetirizine. Nabilone may increase the central nervous system depressant (CNS depressant) activities of Levocetirizine. Levocetirizine may increase the central nervous system depressant (CNS depressant) activities of Orphenadrine. Levocetirizine may increase the sedative activities of Metyrosine.