Drugs MUST have some ability to dissolve in WATER to move around (be absorbed, reach sites of action). In almost all cases, drugs must also have a certain degree of lipid solubility to move around (leave and enter capillaries, enter and leave cells).
Solubility is a preference not an absolute. "Water Soluble", "Lipid Soluble"
Drug effects are USUALLY proportional (though not always linear) to drug concentration at the site of action.
Drug concentrations in the blood stream (measured in either serum or plasma) are USUALLY proportional (and usually linear) to drug concentrations at the site of action.
Drug concentration in the blood stream is ALMOST ALWAYS an excellent predictor of drug action (either efficacy or toxicity) even though they may not be identical to the concentration in the target tissue.
Pharmacokinetics are the consequence of physiologic processes (that may or may not be altered by disease).
"Species differences in pharmacokinetics are the PRIMARY difference between Veterinary pharmacology and Human pharmacology". Disease-induced differences are the PRIMARY difference between basic and clinical pharmacology.
Do you understand proportional? linear? equillibrium?
