Drug permeability

Drug permeability refers to the ability of a drug to pass through biological membranes. It is a crucial factor in drug design and drug delivery, as it affects the drug's bioavailability, distribution, and elimination from the body.

Overview

Drug permeability is determined by several factors, including the drug's chemical structure, lipophilicity, molecular weight, and the presence of transporter proteins in the membrane. The lipid bilayer of cell membranes is a significant barrier to drug permeability, particularly for hydrophilic drugs.

Factors affecting drug permeability

Chemical structure

The chemical structure of a drug can significantly affect its permeability. For example, drugs with a high degree of polarity are generally less permeable to cell membranes.

Lipophilicity

Lipophilicity is a measure of a drug's affinity for lipid environments. Drugs with high lipophilicity are more likely to permeate cell membranes, as these membranes are primarily composed of lipids.

Molecular weight

In general, drugs with a lower molecular weight have higher permeability. This is because smaller molecules can more easily navigate the complex structure of the cell membrane.

Transporter proteins

Transporter proteins can significantly affect drug permeability. These proteins can facilitate the transport of certain drugs across the cell membrane, increasing their permeability.

Measurement of drug permeability

Drug permeability can be measured using various in vitro and in vivo methods. In vitro methods include the parallel artificial membrane permeability assay (PAMPA) and the Caco-2 cell permeability assay. In vivo methods include the intestinal perfusion method and the brain uptake index (BUI) method.

Drug design and delivery

Understanding drug permeability is crucial in drug design and drug delivery. By designing drugs with optimal permeability, scientists can increase the drug's bioavailability, improve its distribution within the body, and control its elimination from the body.

See also

• Bioavailability
• Drug design
• Drug delivery
• Pharmacokinetics