What is drug distribution?
Distribution describes the movement of a drug from the bloodstream after absorption into the body’s tissues. As the drug circulates around the body, its movement into the tissues depends on a number of factors:
- Solubility of the drug – lipid-soluble drugs tend to concentrate in adipose tissue and water-soluble drugs (eg atenolol) tend to concentrate in blood and interstitial fluid. The solubility also has an effect on the rate of distribution, with lipid-soluble drugs usually crossing membrane barriers at a quicker rate.
- Protein binding – some drugs circulate freely in blood plasma and others are reversibly bound to proteins, mainly albumin, alpha-1 acid glycoprotein and lipoproteins. Only unbound drugs can readily cross cell membranes into the tissue where it exerts its action.
- Regional blood flow –