Probenecid in CSF and plasma of rabbits and dogs measured by radioimmunoassay.

Probenecid (P) in CSF of rabbits and dogs was investigated using a new radioimmunoassay technique. In rabbits, under steady-state conditions, CSF/free plasma concentration ratios of P were found to be similar to those reported in man. The ratios were concentration dependent and less than 0.5 suggesting an inhibition of transport of the drug in CNS. Under nonsteady-state conditions, no clear evidence of a transport system was found in dogs.