One role of the anaesthetist in the operating theatre is to maintain adequate levels of muscle relaxation using drug administration. The paper describes extensions to successful online control of muscle relaxation involving the use of Smith predictor and self-tuning algorithms. Extensive simulations including nonlinear pharmacological effects were performed to validate software for clinical trials. Successful clinical experiments were performed using Smith predictor and explicit self-tuning programmes. Careful jacketing of the self tuner was required, and, together with persistent excitation, gave online tracking of drug concentration changes.