What Is the Difference Between Extended Release and Sustainable Release? (Facts Explained)

You could have seen other letters, such as SR, ER, and CR, following the medication’s name if you’ve ever taken an oral medication like a pill or capsule.

You might be asking what they signify or whether they alter the way the drug functions. A modified-release dose form is identified by these letters. 

There are numerous distinct pharmaceutical dosage forms, and each one has special qualities, advantages, and disadvantages to meet your particular needs.

The same is true for dosage forms with modified releases, which alter how the drug enters your body. 

This page will go through the various modified-release dose forms, how they function in the body, and the most effective manner to take them.

What Is Extended Release?

The letters “ER” or “XR” are typically added to the end of the name of an extended-release drug. Medications with ER versions are made to stay in your body for a longperiodime.

Compared to the IR form, this enables the drug to be taken less frequently, thus you may just take 1 to 2 doses each day as opposed to 3 to 4. 

There are ER versions of many different drugs, including venlafaxine ER. Unlike venlafaxine IR, which is taken two to three times a day, this ER antidepressant is only taken once daily. 

Since both types of pharmaceuticals allow for fewer daily dosages, the term “extended release” is frequently used as an umbrella word and can include both sustained- and controlled-release drugs.

How Do Extended Release Drugs Work?

After taking a dose, your body starts to naturally remove the medicine from your system because the liver or kidneys typically break it down.

Extended-release pills, however, featured unique coatings or mixers that make sure that the medication takes longer to leave your system than regular tablets.

There are currently around 30 drugs just for pain relief that are available as extended-release versions of numerous conventional pharmaceuticals. 

The immediate release medications are clearly seen in bloodstream spikes. Tablets with extended releases fix this issue.

Although XR formulations typically take a little longer to kick in than their immediate release counterparts, they keep medication levels in your body more stable.

This translates to longer-lasting, better therapy results, and a lower risk of side effects. Extended-release medications also have the benefit of requiring fewer doses, which is helpful for those who frequently forget to take their prescription, especially when many doses are required throughout the day.

Extended-release, take longer to take effect
Extended-release formulations may take longer to take effect

Are Extended Release Drugs Expensive?

Because of their price. Extended-release formulations typically go through new medication approval with the FDA and pharmaceutical boards and are then given an additional patent as a new drug.

Consequently, the XR version is typically more expensive because there isn’t a comparable generic product. Some XR analogs are nearly ten times more expensive than generic versions.

This, however, is not always the case. Common drugs like Xanax are available in generic form and only cost about twice as much as their official versions.

When you consider the number of pills, it can be less expensive depending on how frequently you take your medications.

Additionally, keep in mind that some health insurance policies only cover conventional immediate-release medications; thus, with your insurance company or your pharmacy.

What Is Sustained Release?

Sustained release tablets are a type of dosage where medicine is given to a patient at a set or calculated rate with the goal of keeping the administered drug’s concentration in the patient’s system for a set period of time while minimizing potential side effects. 

Tablets with a sustained release have a more regulated release. This occurs when a capsule is created and then packed with various little medicine pellets with coatings that won’t disintegrate right away after administration but instead take some time to release their contents at a set rate.

Time-release medications, which include sustained release pills, can either be released completely or in modest amounts after delivery.

They consist of capsules and pills. The formulations, timing, and rate of administration are predetermined to minimize impacts on blood levels, minimize effects on the intestinal system, and possibly even lengthen the half-life of the medication.

A steady level of medication in the body is made possible by sustainable release
The ability to maintain a steady level of medication in the body is made possible by the sustainable release

What Are the Other Different Types of Modified-Release Dosage Form?

An immediate-release (IR) drug is the oral dosage form that is used most frequently. An IR drug typically dissolves soon after entering the body and acts quickly for a brief period of time, however, there are notable exceptions. 

IR drugs are fast absorbed and reach their maximal levels. As your body eliminates the medication, the levels will decrease. As a result, your body’s medication levels after a dose vary.

To keep a constant level of medication in your body, you might need to take several doses of various medications in a single day.

Numerous various dosage forms have been developed to lengthen or postpone the effects of drugs in order to make them more convenient and more tolerated.

These are referred to as modified-release dose forms, and understanding the distinctions between the most popular ones is crucial.

  • Controlled Release
  • Delayed Release

Controlled Release (CR)

Typically, a controlled-release medication’s name is tagged with “CR” after it. The active ingredient(s) in CR drugs are released at a specified rate to maintain consistent medication levels in your body for a predetermined amount of time.

Fewer doses are required throughout the day and medicine levels can be controlled more precisely after taking it. 

Unlike SR dosage forms, CR drugs allow you to precisely control both the release of the drug and how much is present in your body at any given time.

One example of a CR drug is the sedative Ambien CR (zolpidem ER). Some people might not be able to obtain a good night’s sleep because Ambien IR tends to wear off later in the night. Contrarily, Ambien CR delivers the drug gradually over the course of the night to encourage better sleep.

Delayed Release (DR)

Medication with a delayed release (DR) is one that releases the active ingredient(s) later after consumption, allowing for more precise control over the site of release in the body (e.g., small intestines).

Usually, this is done to delay the medication’s early breakdown or decrease any potential adverse effects. 

In order for the active ingredient(s) in some DR drugs to reach the area being treated, the large intestine (the colon) must first be opened up.

Sulfasalazine DR, for instance, is a drug used to treat ulcerative colitis, an inflammatory disorder that results in colon inflammation.

EC or “safety-coated” drugs are also regarded as DR dosage forms because of their enteric coating. They don’t break down in the stomach because of a distinctive film covering.

This prevents the medication from being released until it reaches the small intestine, which may help lessen certain side effects, like an upset stomach. There is an EC variant of the widely used drug aspirin.

Sustained release medicine has longer side effects
As the medication is released for a longer period of time with sustained release, side effects can last considerably longer

Disadvantages of Modified-Release Dosage?

Here’re some disadvantages of modified release dosage:

  • Hard to swallow for some people.
  • More expensive 
  • May take more time to get out of your system.
  • It can’t be altered, cut, or split. 
  • Might be hard to modify your dose if power isn’t available. 

Difference Between Extended Release and Sustained Release

However, it doesn’t seem like there is much of a difference between the two formulations. The objective is to ensure a consistent release of the active component over a long period of time.

It would alter the physiological disposition of the medicine in vivo if properly designed and dependent on the type of substance. Sustained-release (SR) and controlled-release (CR) dosages make up the extended-release dosage.

  • Drug release is maintained by SR for an extended period, although not at a steady pace. A fairly constant rate of drug release is maintained by CR over an extended duration. 
  • To maintain a steady drug concentration for a set amount of time with the fewest adverse effects, sustained-release dosages are dosage forms created to release or liberate a drug at a specified rate.
  • Several formulations, such as liposomes and drug-polymer conjugates, can be used to accomplish this (an example being hydrogels). The definition of a prolonged release more closely resembles a controlled release.
  • You might take a medicine called sustained release every 6 to 8 hours. Sustained drugs guarantee that the quantity of the drug in your body remains constant from hour 1 to hour 6.
  • Extended-release drugs may last longer than sustained-release pharmaceuticals and may experience a dip in blood levels before the next dose.
  • Although there are situations when extended-release lessens the likelihood of negative effects. But in actual actuality, they are quite close to being about the same with only tiny variances.

Here’s a table that shows the advantages of extended-release and sustainable release:

Extended ReleaseSustainable Release
The total dose is reducedReleases into the bloodstream more gradually
Reduced GI side effectsEnables the maintenance of a steady level of medication in the body
Reduce dosing frequencyThe risk of burst drug release is eliminated
Enhance patient compliancesReduce side effects
Less fluctuation at plasma drug levelsLessens the disturbance of sleep caused by pain breakthrough
Reduction in overall health costGives patients a better experience because they don’t have to take medicines every 4-6 hours
Benefits of extended-release and sustainable release.
Watch This Video to Know About Sustained and Control Release Drug Delivery System


  • Extended-release drugs work by slowly releasing their active ingredients into the body over several hours or days. Usually, they come in the form of an oral tablet or an oral capsule. 
  • They differ from drugs with an immediate release, which starts working shortly after consumption. 
  • Typically, the letters “SR” are added to the end of the names of drugs for sustained release. 
  • To provide you with the benefits of the drug over a longer length of time, these medications delay the release of the medication from a tablet or capsule.
  • It could take longer for modified-release drug formulations to begin working. This is because they are frequently absorbed more gradually or do not begin to break down until they reach a specific location in your body. 
  • Several modified-release drug formulations (such as ER, SR, and CR) have effects that persist longer.

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