Choosing the Right Enteric Capsule

What are Enteric Capsules?

Enteric capsules are designed to withstand the acidic environment of the human stomach during the digestive process until they reach the next step of digestion.

Enteric formulas were originally developed to administer medicines that tasted badly or caused gastric discomfort. If patients could not consume a medicine without vomiting due to its horrible taste, the patient could not be treated. The first attempts to remedy this situation used substances that were not affected by stomach acid such as fats, waxes, and paraffin. This was only partially effective as part of the pills still dissolved. Little progress was made until the late 1800s when Keratin was introduced as a pill coating, although it was later determined that they weren’t able to fully withstand gastric digestion.

People taking Enteric capsules, known as extended-release tablets, are instructed to swallow the tablet whole and not chew it, which may release the contents all at once, degrading the medication or supplement’s effectiveness.

A capsule that passes successfully through the stomach without dissolving has many applications, but is most often used when:

1. The lining of the stomach must be protected from potentially harmful or irritating substances. Irritating the lining of the stomach can cause nausea, vomiting, and potential injury. The reverse is also true, enteric coatings protect the drug from the stomach and it’s acidic environment.

2. The substance contained within the capsule must reach a lower part of the digestive tract before dissolving to successfully administer the intended contents. For example, some medications used to treat intestinal disorders must reach the intestines before the capsule dissolves. This allows the medication to retain its integrity and potency until it reaches the treatment site.

Enteric capsules or tablets are usually coated after production, hence you’ve seen “safety coated” aspirin in the store. This “safety coating” is made from a compound called HPMCP. It is this compound that resists the acid of the stomach and breaks down only in the small intestine thereby protecting the stomach from the contents of the capsule or tablet. This is commonly used for probiotics. This is an extra step in the production process which often leads to longer production times and increased production costs, which trickle down into the prices of
these capsules.

Capsuline enteric capsules are unique in that they have the HMPCP directly in the formulation and thus do not require a subsequent coating process. This simplifies the production process, lowers costs, and speeds production times for our customers.

How do Enteric Capsules Work?

Enteric capsules work by utilizing the different acidic and alkaline pH characteristics of the different parts of the human digestive tract. The human body’s overall pH hovers around the neutral range of 7, but different parts of the body have varying internal pH levels.

The human stomach is acidic, with a pH of 1.5-3.5. This high level of acidity is what enables your stomach to breakdown the foods you eat for proper digestion.

After the stomach, the acidity decreases to an almost neutral level in the duodenum, before the pH increases in the small intestine to the slightly alkaline pH 7.4. Capsuline Enteric capsules are made with plant-derived HPMC and HPMCP, the latter is the enteric ingredient that only breaks down in environments with a pH of 5.5 or higher, allowing the capsule to pass through the acidic environment of the stomach (pH of 1.5-3.5) without dissolving.

This means that they pass through the stomach intact, and then dissolve approximately one to two hours after ingestion when they reach the alkaline environment of the small intestine.

Enteric Coated Capsules are acid-resistant by design. Enteric Capsules are not the same as the “acid resistant” products that are simply vegetarian capsules with 5% gellan gum; these other products fail to meet pharma dissolution requirements.

What are the Benefits of Enteric Capsules?

Enteric Capsules, for some formulations,  are an ideal choice. This is because they:

  • Do not dissolve in the mouth. Enteric Capsules are ideal for drugs that are acid-activated, as they prevent the drug from activating in the mouth or esophagus. This also prevents an after-taste when an enteric capsule is swallowed.
  • Do not irritate the stomach. Many common drugs, such as aspirin, can irritate the stomach. Because they pass through the stomach intact, Enteric Capsules avoid this problem.
  • Preserve enzyme activity. Most tablets break down in the acidic environment of the stomach. Unfortunately, depending on the product’s formulation, this acidic environment can also negatively impact the desired enzyme activity. Enteric Capsules protect the enzymes so that they can be absorbed, at their highest activity levels, in the small intestine.
  • Take longer to dissolve. While most capsules dissolve within 15 minutes, Enteric Capsules do not break
    down until they reach an environment with the proper pH level. Rate of digestion is highly dependent on the contents and fullness of one’s stomach. Reaching the small intestine can take up to 7 hours, so this aspect is important for proper administration.

Capsule Quality Makes a Big Difference

It is important to note that not all Enteric Capsules are equal. To prove this, Capsuline asked an independent lab to conduct some experiments comparing Capsuline’s Enteric Capsules (which were labeled the “reference capsule”) to the leading competitive capsule (called the “test capsule”). The results were quite surprising.

First both capsules were placed in an extremely acidic solution with a pH of 1.2. After four hours in this solution, the competitor’s test capsules had released most of their active ingredients. In contrast, Capsuline’s reference capsules released very little active ingredients. They were still intact, with no signs of significant rupture.

Dissolution of Enteric Capsule in SGF (Simulated Gastric Fluid), pH 1.2

The green line is Capsuline’s Enteric Capsule. The blue line is our competitor’s coated enteric capsule.


Next both capsules were placed in a highly alkaline solution with a pH of 6.5. Capsuline’s reference capsules released their active ingredients almost immediately, while the competitor’s capsule had a significant lag time before its active ingredients were released.

Dissolution of Enteric Capsule in FaSSIF (Fasted Stated Simulated Intestinal Fluid), pH 6.5 

The green line is Capsuline’s Enteric Capsule. The blue line is our competitor’s coated enteric capsule.


Enteric capsules have a number of important benefits and allow the release of medications and supplements after the stomach in the intestines.

Knowing the source and formulation of your capsule is important because how the capsule is manufactured affects how it’s contents are absorbed. Your capsule helps determine how effective the contents are which makes choosing the right entreric capsule a critical decision.

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