Drug Delivery Dynamics: A Closer Look at Extended Release vs. Sustained Release Tablets

Comparing Sustained Release and Extended Release to Other Types

Sustained release and extended release are relative terms. Before we discuss extended release vs. sustained release, it would be helpful to understand the other types of medication they're compared to.

Immediate Release (IR)

Immediate-release tablets are exactly what they sound like. The medication is released soon after the pills are ingested. The drug works quickly over a short period. When IR tablets are prescribed, patients are often required to take several doses daily to ensure a constant supply of medication.

Controlled Release (CR)

Controlled-release tablets are a type of medication designed to gradually release a drug into a patient's system over a certain period. This differs from conventional immediate-release tablets that release their active ingredients as soon as they are ingested.

Controlled-release systems can maintain a constant drug concentration over a prolonged period, reduce the frequency of dosing, minimize side effects and enhance the efficacy of the medication. They can be especially useful in place of drugs that need to be taken several times a day or for conditions that require a constant level of medicine in the bloodstream.

Ambien CR is one example of a controlled-release drug. While Ambien IR can wear off before the night ends, Ambien CR delivers a constant rate of medication, ensuring a good night's sleep from start to finish.

The design of CR tablets can vary greatly, with some utilizing different drug coatings, materials or technologies to control the rate, location or timing of drug release.

Delayed Release (DR)

Delayed-release drugs are designed to release the active ingredient later than immediately after administration. This delay could be based on a certain period after ingestion or until the drug reaches a specific part of the gastrointestinal tract. The design of delayed-release tablets allows the medication to bypass certain areas of the digestive system, which can be beneficial for drugs that are destroyed by stomach acids or for medicines that can irritate the stomach lining.

One example of a DR drug is sulfasalazine DR, used to treat ulcerative colitis.

While delayed-release formulations are designed to control when the drug is released, they don't necessarily control the rate at which it is released once the delay period has ended. In other words, once the drug is released, it may spread rapidly or all at once, differentiating these formulations from sustained-release and extended-release tablets.

Pulse Release

Pulse-release drugs, also known as pulsatile-release drugs, are a type of medication designed to release the active ingredients in a predetermined pattern over a specific period. This can involve one or more "pulses" of drug release to mimic the body's natural rhythms, respond to a particular physiological need or optimize the drug's therapeutic effect and minimize side effects.

The release mechanism can be designed to respond to a variety of factors. For example, it can be programmed based on time (time-controlled release), or it can react to specific physiological signals such as pH changes in different parts of the gastrointestinal tract (pH-dependent release) or the presence of certain enzymes or substances in the body (chemically-induced release).

This type of drug delivery system can be particularly beneficial for conditions that follow a circadian rhythm (like rheumatoid arthritis, where symptoms are often worse in the morning) or for situations that require a burst of medication at specific times (like peptic ulcer disease, which might require a release of drug in response to a rise in gastric acidity).

One example of a pulse-release drug is Prednisone chronotherapy for rheumatoid arthritis. The prednisone is formulated to release the drug in the early morning hours when symptoms are most severe.