> just be the agonistic/antagonistic affinity for every neuro-receptor Except that pretty much every receptor subtype, every transporter protein and many other

> just be the agonistic/antagonistic affinity for every neuro-receptor Except that pretty much every receptor subtype, every transporter protein and many other brain genes exist in multiple variations in the human population, and those variations do alter the way these proteins act. This is one reason why different drugs affect different people differently, because at the lowest level, you don't have the same brain chemistry as other people, there are an infinite number of possible variants.