Drug distribution

Drug distribution is the process by which a drug is transferred from the site of administration to the various tissues of the body. The distribution of a drug between tissues is dependent on vascular permeability, regional blood flow, cardiac output and perfusion rate of the tissue and the ability of the drug to bind tissue and plasma proteins and its lipid solubility.

Pharmacokinetics

Pharmacokinetics is the study of how an organism affects a drug. Drug distribution is a part of pharmacokinetics which involves the movement of drug into and out of the bloodstream and from the bloodstream into cells.

Factors affecting drug distribution

Several factors can affect the distribution of a drug within the body. These include:

• Plasma protein binding: Drugs can bind to plasma proteins for transport. Only unbound drug is active; bound drug is effectively "stored".
• Blood flow: Organs with a good blood supply pick up the drug quickly.
• Lipid solubility: Highly lipid-soluble drugs can penetrate cell membranes more easily, and hence, can be distributed more widely.
• Molecular size: Large molecules may not be able to cross certain barriers, such as the blood-brain barrier or placenta.

Drug distribution models

Drug distribution is usually described by models, such as the one compartment model, two compartment model, and multi-compartment model. These models are mathematical representations of the actual distribution of drugs in the body.

Drug distribution and disease

Disease states can affect drug distribution. For example, in patients with kidney disease or liver disease, drug distribution may be altered, leading to changes in the individual response to medication.

See also

• Pharmacodynamics
• Pharmacology
• Pharmacotherapy
• Pharmaceutics

Drug distribution Resources
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