Drug carrier
（重定向自Drug carriers）
A drug carrier is any substrate used in the process of drug delivery which serves to improve the selectivity, effectiveness, and/or safety of drug administration. Drug carriers are primarily used to control the release of a drug into systemic circulation. This can be accomplished either by slow release of the drug over a long period of time (typically diffusion) or by triggered release at the drug's target by some stimulus, such as changes in pH, application of heat, and activation by light. Drug carriers are also used to improve the pharmacokinetic properties, specifically the bioavailability, of many drugs with poor water solubility and/or membrane permeability.