Lipid Soluble and Insoluble Drug

A lipid insoluble drug will have poor gastrointestinal absorption, may need to be given parenterally, has limited distribution (may not cross blood-brain barrier or placenta and less likely to be stored in fat tissue), may be eliminated without metabolism, and will often have a short plasma half-life as elimination does not require metabolism.

By contrast, a lipid soluble drug will have good gastrointestinal absorption, can be give orally, will be widely distributed in the body, usually requires metabolism before elimination (to decrease lipid solubility), and will often have a long plasma half-life (prolonged by ‘reservoir’ of drug in tissues and by requirement for metabolism).