Pharmacology: Pharmacokinetics: Peak blood levels of the order of 0.3 microorganisms/mL are reached between thirty and sixty minutes after oral administration at a 10 mg dose of Cetirizine Dihydrochloride. Its plasma half-life is approximately 11 hours. Absorption is very consistent from one subject to the next. Its renal clearance is 30 mL/minute and the excretion half-life is approximately nine hours. Cetirizine Dihydrochloride is strongly bound to plasma proteins.