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Sustained release's definition is more akin to a "controlled release" rather than "sustained". Extended-release dosage consists of either sustained-release (SR) or controlled-release (CR) dosage. SR maintains drug release over a sustained period but not at a constant rate. CR maintains drug release over a sustained period at a nearly constant ...
Controlled or modified-release formulations alter the rate and timing at which a drug is liberated, in order to produce adequate or sustained drug concentrations. [28] The first controlled-release (CR) formulation that was developed was Dexedrine in the 1950s. [ 13 ]
The history of gated drug delivery systems starts in the mid-1960s when the concept of zero order controlled drug delivery was first thought of. Researchers raced to be able to find a drug delivery platform that would be able to have perfectly sustained drug release.
The concept of stimuli-responsive drug delivery systems can actually be seen as ahead of this time, since the first pH-responsive drug coating was used in the late 1950s in Europe. [4] These coatings were used on drugs delivered to the stomach, so that they would protonate and dissolve at low pH to release drug. [4]
Controlled drug release systems can be achieved through several methods. Rate-programmed drug delivery systems are tuned to the diffusivity of active agents across the membrane. [44] Another delivery-release mechanism is activation-modulated drug delivery, where the release is triggered by environmental stimuli.
In other sustained release formulations the matrix swells to form a gel through which the drug exits. Another method by which sustained release is achieved is through an osmotic controlled-release oral delivery system, where the active compound is encased in a water-permeable membrane with a laser drilled hole at one end. As water passes ...
Dextran prodrugs are chemically linked drug-polymer complexes in which enzymatic processes and hydrolysis in vivo cause the drug to become pharmacologically active. Therapeutic agents can be linked to dextran via an ester bond which can be hydrolyzed slowly by esterases to produce sustained, stable drug release. Drug-dextran complexes can also ...
The drug is expelled via the laser-drilled hole visible on the left side of the tablet. The osmotic-controlled release oral delivery system (OROS) is an advanced controlled release oral drug delivery system in the form of a rigid tablet with a semi-permeable outer membrane and one or more small laser drilled holes in it.