This paper considers the steady-state plasma drug concentration in a one-compartment, open pharmacokinetic model with multiple doses and first-order kinetics using a classical deterministic technique as well as a queueing theoretical stochastic analysis. The stochastic analysis employs a new method for obtaining the steady-state probability distribution of the content of a dam with compound Poisson input and a general release rule. It is shown that if the deterministic steady-state average concentration exists, it is equal to the mean value of the steady-state concentration, the probability distribution of which is obtained using the stochastic model. Moreover, the steady-state probability distribution of the concentration and its mean always exist in the stochastic model. Ramifications of the stochastic method of analysis are discussed.