Control on the cellular level is a vital function that enables a biochemical reaction to choose the direction it will go, to shut off when a function has been fulfilled, to assure a feedback, or even to interpose a block to a feedback. Control mechanisms are usually biochemical functions which direct such action. They are influenced by a variety of factors—sometimes temperature or pH changes, but, more particularly, they are influenced by drugs.
In fact, the ostensible purpose of drug administration is to control an anomalous state—either by hastening a reaction, protecting it from change, or reversing it. The same principle is also in therapeutics: the purpose of a drug is to control disease by enhancing a body function, preventing an anomalous development, or reversing it. Such control takes place when a drug interferes with or enhances a biochemical event.
To be able to exercise that control of physiological functions