Time release technology

Retard (Latin:. Slowed acting; engl sustained release (SR ), extended release (ER, XR), controlled / continuous release (CR ) ) refers to a dosage form in which the drug is released slowly. In contrast to depot dosage forms is meant by slow release drugs in the narrow sense orally administered dosage forms. Both terms are often used interchangeably but each other. Drugs that are taken delayed due to their pharmacokinetic properties or in case of prodrugs only converted by the body into its active form, but they are not slow release drugs.


The Pharmaceutical Technology offers a number of ways to produce sustained-release preparations. The simplest form is a tablet with a special coating, such as are used for example in gastric juice-resistant drugs. Widespread is the sustained-release capsule, the small drug-containing sustained-release beads ( pellets ) that that can be released after dissolution of the capsule shell. Tablets are also increasingly used in which pellets are pressed to tablets ( multiple unit pellet system ( MUPS ) ). More complex forms of the drug store in a slowly eroding matrix. Another way of retardation is the oral osmotic system.

Time course of release

By retarding drug forms is defined temporal profiles of drug release can be achieved. Common examples are:

  • Sustained release - release at a constant speed
  • Prolonged release or slow release - release with decreasing speed
  • Delayed release - delayed release

Sometimes in a single tablet or capsule, sustained-release forms with a fast acting initial dose (bolus ) are combined.


Areas of application are, for example, by blood pressure drugs or hormones. Retardances are used to prevent harmful short-term high levels of drugs in the blood ( plasma peaks ) and / or to achieve the longest possible effect of a drug from a single dosage form. By avoiding plasma peaks Side effects are rare, and can be reached by the long effect that a patient the medication less frequently, for example, only once has to take on the day, which increases compliance.

Other mechanisms of retardation

The term sustained-release preparation in the narrow sense usually refers to perorally to be taken special dosage forms. The same effect can also be achieved by long-term preparations, in which the drug itself has been chemically modified in order to achieve a slower effect. Even depot preparations for parenteral use have a delayed effect by slow release, for example, from muscle tissue into the bloodstream.