Development of antiviral levels of ribavirin in serum and urine of orally treated rats.

The levels of ribavirin or its antivirally active metabolic products were determined in the serum and urine of rats treated with single oral doses of 1,000 or 100 mg/kg of the compound, using a newly developed micromethod in which measles virus inhibition was assayed in BS-C-1 cells. At the high dosage level, maximum ribavirin serum levels of 24 microgram/ml were observed 2 h postribavirin administration. Approximately 10-fold less active material was seen in the rats receiving the lower ribavirin dosage; this peak effect was seen 1 h after treatment. Urine excretion was maximal between 4 and 20 h after treatment in both dosage groups.