The disposition of radioactivity has been studied after administration of single and repeated oral or subcutaneous doses of [14C]LAS to rhesus monkeys. After single 30 mg/kg oral doses the radioactivity was rapidly excreted, mostly during the first 24 h. Means of 71.2% and 23.1% of the dose were excreted in the urine and faeces respectively during 5 days. Similarly, after single 1 mg/kg subcutaneous doses, means of 64.1% and 10.9% were excreted in urine and faeces respectively during 5 days, mostly during the first 24 h. After single oral doses of 30, 150 and 300 mg/kg peak plasma concentrations, at 4 h in all cases, were very similar representing 34, 41 and 36 μ/ml respectively. After single subcutaneous doses of 0.1, 0.5 and 1 mg/kg, peak plasma concentrations increased almost proportionately and represented 0.16, 0.72 and 1.13 μg/ml respectively. During 7 consecutive daily oral (30 mg/kg/day) or subcutaneous (1 mg/kg/day) doses, there was no accumulation of radioactivity in plasma. Mean peak concentrations and biological half-lives were similar after the first and seventh doses. After 7 doses of [14C]LAS, there was no localisation of radioactivity in any tissue. No unchanged LAS was detected in urine samples after oral or subcutaneous doses. About 5 major radioactive components were detected in urine extracts; all were apparently more polar than LAS, but were not sulphate or glucuronide conjugates. © 1978 Elsevier/North-Holland Scientific Publishers Ltd.
