Passive Diffusion

This is the most important means by which a drug enters the tissues and is distributed through them. It refers simply to the natural tendency of any substance to move passively from an area of high concentration to one of low concentration. In the context of an individual cell, the drug moves at a rate proportional to the concentration difference across the cell membrane, i.e. it shows first-order kinetics (see p. 99); cellular energy is not required, which means that the process does not become saturated and is not inhibited by other substances.

The extent to which drugs are soluble in water or lipid is central to their capacity to cross cell membranes. Water or lipid solubility is influenced by environmental pH and the structural properties of the molecule.

Blood Pressure Health

Blood Pressure Health

Your heart pumps blood throughout your body using a network of tubing called arteries and capillaries which return the blood back to your heart via your veins. Blood pressure is the force of the blood pushing against the walls of your arteries as your heart beats.Learn more...

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