Chemo Drugs supplies Levocetirizine Dihydrochloride Pharmaceutical Tablets. Chemo Drugs is an ISO 9001:2000 accredited company. The Levocetirizine Dihydrochloride Pharmaceutical Tablets are active enantiomer of cetirizine. Levocetirizine works by blocking histamine receptors. Levocetirizine Dihydrochloride Pharmaceutical Tablets does not prevent the actual release of histamine from mast cells, but prevents it binding to its receptors. This in turn prevents the release of other allergy chemicals and increased blood supply to the area, and provides relief from the typical symptoms of hayfever.