Different species respond differently to the same drug. Drug responses can vary among various strains or races within a species. The sex of an individual can affect drug responses. Aging changes the effects produced by drugs. Diseases that affect circulation, distribution, metabolism or excretion can change the individuals response to drugs.
Nutritional factors can influence drug effects.
Biorhythms or cycles in biological activity can interact with drug effects. In addition, temperature, posture, and water retention can influence drug effects. J. Psychological factors can influence drug effects. The set or expectations of the user can influence drug effects. The personality of the user can influence drug effects.