This document outlines the principles and mechanisms of non-receptor mediated drug action. It discusses how drugs can stimulate, depress, irritate or replace cellular activity. The main targets of drug action are enzymes, ion channels, transporters and receptors. Enzymes are proteins that catalyze reactions and drugs can induce, stimulate or inhibit enzymatic activity through various mechanisms like competitive or non-competitive inhibition. Ion channels facilitate ion flow across membranes while transporters control nutrient/toxin influx and efflux. The document provides examples to illustrate how drugs can act through these non-receptor mediated pathways.