Retardation

Controlled release from the drug

The special design of a drug can be used to achieve delayed, prolonged, continuous, and controlled release of the active ingredient over an extended period of time. This allows the timing, location, and rate of release to be influenced.

Galenics

Sustained-release drugs include sustained-release tablets, sustained-release capsules, sustained-release granules, and suspensions. Injectables may also be sustained-release, and transdermal patches release the active ingredient with a delay. The galenics of the products vary. The main methods include:

  • Special coatings with a reservoir in the core.
  • Embedding in a polymer matrix (matrix tablets).
  • Osmotically controlled systems

Tablets and capsules may also contain small granules or pellets with these properties. Enteric coated drugs disintegrate only in the alkaline environment of the small intestine and not in the acidic stomach. This is referred to as delayed release. The various methods are often combined. This text refers to galenic measures. Retardation can also be achieved through active ingredient design. An example is the ADHD drug and prodrug lisdexamphetamine.

Drug names

Sustained-release drugs are referred to and abbreviated by a variety of terms. These include:

  • Retard: retarded (delayed).
  • MR: Modified-Release (modified release).
  • ER: Extended-Release (extended release)
  • SR: Sustained-Release or Slow-Release (sustained release, slow release).
  • CR: Continuous-Release or Controlled-Release (sustained release, controlled release).
  • DR: Delayed-Release (delayed release) or Dual-Release / Duo-Release (dual release).
  • LA: Long-Acting (long-acting).

Other terms include prolonged-release, time-released, extend and depot. From the abbreviations is usually no reliable conclusion about the exact nature of the release.

Stable plasma concentrations

Conventional tablets or capsules without sustained release (IR: immediate-release) disintegrate rapidly, releasing the entire dose for absorption at once. Concentration peaks occur and the concentration curve is characterized by ups and downs with multiple dosing. These dosage forms are particularly suitable for acute therapy. Retardation allows more uniform and flat plasma concentrations to be achieved, reducing the risk of dose-related adverse effects. Fluctuations are avoided and the effect is stabilized. With sustained release, bioavailability may be increased because transport processes are not saturated due to the lower concentrations. Sustained-release preparations may also be designed to have a lower potential for abuse.

Longer dosing interval

Delayed release of the active ingredient extends the dosing interval and, accordingly, the drug needs to be administered less frequently, which can have a positive impact on treatment adherence. Retardation is particularly attractive for active ingredients with an excessively short half-life. Some sustained-release preparations are designed in such a way that an initial dose is released first and a constant plasma concentration is maintained with a controlled release of the second dose. Sustained-release drugs without these features are generally not suitable for acute treatment because the onset of action is delayed.

Disadvantages

Sustained-release dosage forms often must not be divided, chewed, crushed, or pulverized because the entire dose may be released at once and the delay lost. Incorrect handling can lead to intoxication. This limits flexibility. However, some sustained-release tablets are available that may be divided. The manufacture of sustained-release preparations is more complicated and expensive, and not all active ingredients are suitable for such a formulation. Sustained-release preparations are more susceptible to first-pass metabolism. This process can be saturated by normal doses. Low doses released from sustained-release drugs, on the other hand, can be rapidly biotransformed.