Leukovir, an enteric-coated tablet, is the original drug product for internal use. The well-known nucleosides cladribine and ribavirin are the active ingredients of the drug product leukovir. Pharmacokinetic parameters of the drug product for the internal use of leukovir active ingredients have been established. The cladribine half-absorption period was t1/2a = 49.5 h, C0 = 276.4 μg/ml, Cmax = 6.0 μg/ml. Distribution and accumulation parameters (Vd, Vss and AUC) have indicated that the drug distribution between the blood cells and blood plasma takes place in the same way, irrespective of the dosage form. Cladribine half-life period is t1/2e = 0.62 hours. The molecule total clearance and average lifetime in the body in the case of subcutaneous drug administration are approximately the same. Ribavirin is characterized by a half-absorption period of t1/2a = 0.71 h, C0 = 115.6 μg/ml and Cmax = 75.5 μg/ml. Ribavirin total volume of distribution (Vd = 1.3 l/kg) and stationary volume of distribution (Vss = 1.64 l/kg) were practically similar to leukovir when administered subcutaneously. The AUC value = 504.2 μg h/ml, which is 2.5 times less than that in the case of drug form administration. Leukovir was regarded as slightly toxic in an acute toxicity study. The risk of cumulation for this drug product is low.
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