The purpose of this lecture is to introduce the concept of intraoperative and the potential for the postoperative use of constant rate infusions of combinations of low dose analgesic drugs to provide high quality multimodal pain control in small animal patients. This will be done with the introduction of the technique of the Morphine-Lidocaine-Ketamine (MLK) combination. We will begin with a discussion of the mechanism of the mode of action of each analgesic drug. We will discuss the pharmacokinetic principles of constant rate infusion and the concept of the loading dose and achieving a steady state plasma concentration. We will look at the literature for evidence for the efficacy of MLK in clinical situations. Then we will discuss at length how to administer MLK in a simple approach as an additive to the routine intravenous fluid administration or how to tailor it as a separate infusion for longer-term administration for continuous administration into the postoperative period. We will also discuss some common modifications of MLK with other drugs such as fentanyl and others.