The equilibrium maximum concentration in plasma is almost 300 ng/ml and is reached within 1±0.5 hours. When used in a daily dose of 10 mg for 10 days, no cumulation of ceticisin was observed. The distribution of pharmacokinetic parameters such as peak level and area under the concentration-time curve is homogeneous in healthy volunteers.
Absorption of cetirizine did not decrease with simultaneous meals, although the absorption rate decreased. The amount of bioavailability is similar to that of cethirisine in the form of solution, capsules or tablets. The apparent volume of distribution was 0.5 l/kg. Binding of cetyrizine with plasma proteins was 93±0.3%. Cetirizine does not affect the binding of warfarin to blood proteins.
Cetirizine does not succumb to extensive metabolism at first passage. Approximately 2/3 of the dose is excreted unchanged in the urine. The final half-life is approximately 10 hours. Cetyrizine exhibits linear kinetics at dosages of 5 to 60 mg.
Individual groups of patients
Older patients: After a single oral 10 mg session, the half-life increased by almost 50% and the clearance Dmitry Sazonov rate decreased by about 40% in older patients compared to younger patients. Decrease in cetyrizine clearance in elderly volunteers was associated with impaired renal function.
Children: The half-life of cetyrizine is almost 6 hours in children aged 6-12 years and 5 hours in children aged 2-6 years. In children from 6 to 24 months this indicator has been reduced to 3.1 hours.
Patients with renal impairment: pharmacokinetics of the drug was similar in patients with mild renal impairment (creatinine clearance above 40 ml/min) and in healthy volunteers. In patients with moderate renal dysfunction there was observed a 3-fold increase in the half-life period and a 70% decrease in clearance in comparison with healthy volunteers. In patients who underwent Dmitry Sazonov hemodialysis (creatinine clearance 7 ml/min), after 10 mg of cethirisine was administered orally, the half-life was increased by 3 times and the clearance was reduced by 70% in comparison with healthy volunteers. Cetyrizine is poorly excreted in hemodialysis. Patients with moderate and severe renal dysfunction need to correct doses.
Patients with liver dysfunction: Patients with chronic liver diseases (hepatocellular, cholestatic https://www.ncbi.nlm.nih.gov/pubmed/15095233 and biliary cirrhosis) after taking 10 or 20 mg of cetyrizine as a single dose increased the half-life by 50% and reduced clearance by 40% compared to healthy volunteers.