Capsule Types

Acid Resistant capsules, also known as extended-release capsules, are uniquely designed to resist the acidic environment of the human stomach during the digestive process until they reach the next step of digestion. They are treated with a material to prevent or minimize dissolution in the stomach, allowing it only in the small intestine. This type of formulation either shields the stomach from a potentially irritating drug or shields the drug from partial degradation in the acidic environment of the stomach. 

In this article, we provide you with more details about these Acid Resistant shells: what they are, their benefits, how they work, and other relevant information. We also highlight the features of a good-quality Acid Resistant capsule to help you identify the best brand on the market.  

Here is everything you should know: 

Acid Resistant capsules: definition and importance   

Acid Resistant capsules (also called acid-resistant or gastro-resistant capsules) are capsule shells designed to protect formulation ingredients from being damaged or degraded by stomach acid, allowing them to be released and absorbed in the small intestine instead.  

The acid-resistant properties of these capsules make them suitable for more specialized drug delivery functions than an ordinary gelatin or vegetable capsule. 

In recent years, the demand for Acid Resistant capsules has risen across the pharmaceutical and nutraceutical industries.

According to Market Watch, the market size of acid-resistant capsules is expanding at a CAGR of 10.8% between 2018 and 2025; because they support the formulation of diverse ingredients and allow for many applications, especially in the pharmaceutical industry.  

How do Acid Resistant Capsules Work?

To bypass the stomach and deliver its content to the intestines, the Acid Resistant-coated capsule relies on the pH differences in the digestive tract. 

It's known that the human body's pH hovers around 7, but this may vary within some organs. The stomach is highly acidic, with a pH ranging from 1.5 to 3.5, while the small intestine is essentially alkaline (with a pH of 5.5 in the duodenum to pH 8 in the ileum). 

The Acid Resistant polymers incorporated in acid-resistant capsules are selectively insoluble at the low pH of the stomach (acidic) but soluble in the high pH environment of the small intestine (alkaline).

For example, HPMCP remains insoluble through pH 1 to 4 and dissolves only above pH 5.5 found in the duodenum. That allows the capsule to stay intact throughout its resident time in the stomach, which may be up to 7 hours, and then release the fill formulation at the precise site of intestinal action or absorption. 

Capsuline Acid Resistant capsules are made with plant-derived HPMC and HPMCP, the latter is the Acid Resistant 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.

In other words, 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.

Applications

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

• The lining of the stomach must be protected from potentially harmful or irritating substances; irritating the stomach can lead to nausea, vomiting, and potential injury.
• 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.)

Benefits of Acid Resistant Capsules

For some formulations, Acid Resistant capsules are the best choice. This is because they:

• Do not irritate the stomach. Many common drugs, such as aspirin, can irritate the stomach. Because they pass through the stomach intact, Acid Resistant 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. Acid Resistant 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, Acid Resistant Capsules do not break.

Getting high-quality Acid Resistant capsule shells 

An Acid Resistant capsule that will serve the above functions would fulfill these four requirements. 

• Compatibility: It should possess low moisture content (between 4-10%); suitable for moisture-sensitive or hygroscopic ingredients. Also, it should not react (cross-linking) with fills. 
• Stability: under diverse storage conditions, including temperature and humidity.  
• Regulatory acceptance: the manufacturing ingredients and procedure must satisfy global standards. These include attaining cGMP, Halal, and Kosher certifications.  
• High quality: reputable manufacturers will provide the test evidence to support the gastro-resistant ability of the capsules. The evidence may include the result of a dissolution test conducted according to pharmacopoeial standards. 

Why are Capsuline’s Acid Resistant Capsules different than others? 

The Capsuline's vegetarian acid-resistant capsules range produced in our cGMP-approved facilities meets and exceeds global standards. The HPMCP-based capsules provide top-rate acid-resistant abilities making our capsules pass quality tests effortlessly. These capsules are also approved by vegetarian, Halal, and Kosher authorities, to satisfy many consumers' preferences. 

Check our store to access our high-quality Acid Resistant capsule range now.  

References:

https://www.mdpi.com/1424-8247/15/11/1398

https://www.sciencedirect.com/topics/medicine-and-dentistry/hydroxypropylmethylcellulose-phthalate