Acid Resistant Capsules

Do you feel irritation in your stomach when you take oral dosages?

Well, to avoid that, you should embrace the acid resistant capsules.

Today’s guide will take you through all the information about an acid resistant capsule.

What are Acid Resistant Capsules?

Acid resistant capsules are drugs that do not disintegrate in the stomach.
Drug disintegrating in the stomach

Drug disintegrating in the stomach – Photo courtesy: Doctors Lib

It has an enteric coating that prevents the disintegration and dissolution in the stomach gastric environment.

The capsules often deliver the active ingredients straight to the duodenum for intestinal absorption.

They are suitable for delivering enzymatic and probiotic formulations.

History of Acid Resistant Capsules

Initially, stomach acid resistant caps were supposed to help in masking the bad odor and taste to the consumer.

Acidi resistant capsules

 Acid resistant capsules

It was also supposed to help ease the discomfort that consumers felt after consuming the other drugs.

Patients with such conditions were undergoing a lot of trouble when it came to treatment.

Early attempts to solve this problem argued that the drugs reacted with the stomach wax, acids, paraffin, and fats.

So, the main solution was to cover the main ingredients in a capsule shell that is resistant to stomach acids.

The first form of acid resistant capsules had keratin coating.

The keratin-coat could not withstand the stomach acid prompting a change to salol and shellac coating.

Hydrolyzed and properly treated shellac were manifesting different release properties.

In the modern era, manufacturers use supplements of ingredients on omega-3 fatty oils (fish oils) to prevent fish oil digestion.

How Gastric Acid Resistant Capsules Work

Gastric acid resistant capsules work by presenting a stable environment on an extremely acid stomach environment.

How acid resistant capsules work

How acid resistant capsules work – Photo courtesy: INNOVIX LABS

They utilize different alkaline and acidic pH characteristics of the diversity of the human digestive system.

Usually, when you swallow a drug, it might dissolve in the mouth or go straight to the stomach for digestion.


Your body usually has a neutral pH hovering around 7 but other parts have varying pH levels.

The digestion occurs in the stomach with the assistance from the low pH in the stomach between 1.5 and 3.5.

Therefore, gastric acid resistant capsules, will not disintegrate in the low pH environment.

It will pass on to the upper part of the intestine where the pH is higher.

The pH in the upper part of the stomach and the duodenum is almost neutral to slightly alkaline of 7.4.

At this point, the capsule will break its shell and release the active ingredients for treatment.

Other types of gastric acid resistant capsules will pass on to the intended point before breaking and releasing the content.

Types of Acid Resistant Capsules

Acid resistant capsules are available in four different types.

You are likely to come across all these different types because of the different dietary requirements.

Gastric acid resistant capsule manufacturers consider the requirements of the vegans who do not eat animal products.

Here are the types of acid resistant capsules.

Acid resistant capsules

 Acid resistant capsules

· Gelatin Acid Resistant Capsules

The main ingredient in making the outer shell of this capsule is gelatin.

It is suitable for people who do not have restrictions on animal dietary requirements.

In fact, gelatin capsules are very popular.

· Vegan Acid Resistant Capsules

The main ingredient for the outer shell of this acid resistant capsule is a vegetable product such as tapioca.

Veg caps are the best solution for consumers who follow a strict vegan diet and do not consume animal products.

· Pullulan Acid Resistant Capsules

Pullulan acid resistant capsules have capsule caps from fungi that grow on starch substrates.

They are purely vegan capsules suitable for people who do not consume animal products.

They also have a special ingredient that maintains the integrity of the capsule through the harsh acidic stomach environment.

· HPMC Acid Resistant Capsules

HPMC or HPMCP are plant derivatives that will break down in an environment with a pH higher than 5.5.

It is suitable for encapsulating hygroscopic and oil formulas.

This property allows it to pass through a harsh acidic environment ranging between a pH of 1.5 – 3.5.

HPMC acid resistant capsules are also suitable for people who follow strict diets.

What Makes Capsules Resistant to Stomach Acid?

Acid resistant capsules have special formulations and ingredients that delay the release of the capsule content.

The capsules have enteric coatings that will not dissolve in the stomach juices.

The delayed release properties are as a result of exclusive formulations of:

  • Proprietary polymers
  • Hypromellose
  • Zein
  • Sodium Alginate
  • Shellac
  • Cellulose acetate trimellitate
  • Polyvinyl acetate phthalate (PVAP)
  • Cellulose acetate succinate
  • Cellulose acetate phthalate
  • Hydroxypropyl methyl cellulose phthalate

These exclusive formulations are resistant to acidic conditions but can react well in alkaline environments.

It is the reason why the capsules pass through the acidic conditions in the stomach and disintegrate in the duodenum.

Different manufacturers use different combinations of the formulations to make the capsule resistant to stomach acids.

Benefits of Stomach Acid Resistant Capsules

I guess you might be asking why you need to use the stomach acid resistant capsules.

Well, some of the advantages of using these capsules include:

swallowing capsules

Swallowing capsules

· Easy to Swallow

Just like any other form of capsule, acid resistant capsules are very easy to swallow.

You may not need to wash it down your throat with a glass of water.

· Delayed Release

Stomach acid resistant capsules have special ingredients that delay the release of the active inner fill materials.

It delays the release until the capsule reaches the right conditions for disintegration and release of inner fill materials.

This property makes it a good drug for time sensitive medications.

· Resistant to Gastric Acids

The delayed properties are as a result of the enteric coating that is resistant to gastric acids.

· Low Moisture Content

It has low moisture content thus improving the stability of the capsule for a longer period.

The low moisture content increases the shelf life of the acidic resistant capsules.

· Resistant to Cross-linking

The active ingredients on the enteric coating prevent the alteration of gelatin coat thus preventing capsule disintegration.

The capsule resists cross-linking in an acidic environment but it will disintegrate in alkaline conditions.

· Stability Over a Wide Range of Humidity and Temperature

Acid resistant capsules maintain its stability over a wide range of temperature and humidity.

It will lose the stability once it gets to an environment that has favorable humidity and temperature.

· Wide Regulatory Acceptance for Pharmaceutical Applications

Acid resistant capsule manufacturers use products that are accepted by a wide range of regulatory bodies.

The ingredients are safe for human use thus acceptable for a wide range of applications.

· Protecting the Stomach Lining

The capsules also protect the integrity of the stomach lining.

Such properties make it an important drug for people experiencing irritations whenever they use other capsules.

· Delivery of Intended Contents at the Right Point

Acid resistant capsules have special properties that ensure that it reaches the right point before it disintegrates.

Such properties allow it to pass through different humidity, temperature, and pH conditions until it reaches the right environment.

Drawback of Gastric Acid Resistant Capsules

As much as it is beneficial in a number of ways, acid resistant capsules also have its drawbacks.

The main drawbacks of the acid resistant capsules include:

Hard gelatin capsules

Hard gelatin capsules

· Delayed Relief from Pain

By delaying the disintegration of the capsule, it also increases the time before a patient gets maximum pain relief.

One has to wait for more than three to four hours after swallowing the pill before getting maximum pain relief.

· Reduces the Ability to Inhibit Blood Clotting

Patients taking acid resistant capsules with the active ingredient of treating heart complications may not get desired relief.

Instead, delayed functions increase the risk of heart attacks as it reduces the ability of the aspirin to reduce blood clotting.

Do not let the demerits discourage you from using the acid resistant capsules.

Gastric Acid Resistant Capsule Sizes in the Pharmaceutical Industry

The pharmaceutical industry allows you to have different acidic resistant capsule sizes.

Implying that there are different sizes of acid resistant capsules available in the market.

There are, however, some limits to the smallest and biggest size of acid resistant capsule you can make.

The size of the acid resistant capsules is in terms of capsule height and the volumetric capacity of the capsules.

In terms of height, you can get an acid resistant capsule as long as two and a half centimeters.

It can also be as short as one and a half centimeters.

Also, the volumetric capacity of the acid resistant capsule also varies in milliliters.

Acid resistant capsule sizes

Acid resistant capsules sizes

The volumetric capacity is also the key determinant of the density of the acid resistant capsule.

For many applications, acid resistant capsules of size 0 or size 00 will be suitable.

They are the sizes of acid resistant capsules that are very common.

For instance:

  • Size 0 will hold 500 mg or 0.5 g of the inner fill materials
  • Size 00 will hold 735 mg 0.735 g or 735 mg of the inner fill materials.

In that case, we have the following sizes of acid resistant capsules:

i. Large Capsules

The largest capsule size is size 000 holding about 1000 mg of inner fill materials.

 ii. Average Capsule Size

The most common capsule size in this category is 00 which holds 750 mg of inner fill materials.

It has a volume of 0.93 ml and maximum size of 23.6mm.

You will also find size 0 capsules which hold 500mg, with a volume of 0.68 ml and 21.3mm long.

iii. Small Capsule Size

Small capsules can either be size 1 holding about 400 mg or size 2 holds about 300 mg.

It is suitable for people who have trouble swallowing capsules and not good for people who want high dosages.

It is very difficult to fill and handle thus making it less popular.

It requires dosator capsule filling machine for micro dosing or filling low weight capsules.

How to Make Delayed Release Capsules

Since there are different types of acid resistant capsule, we are going to look at:

i. Making Acid resistant Softgel capsules or Single Piece Capsules

ii. Making Acid resistant hard capsules or Two Piece Capsules

Acid resistant capsules

Acid resistant capsules

Making Acid Resistant Softgel Capsules

Anatomy of softgel

Anatomy of Softgel

Step One: Making the Acid Resistant Cap

At this stage, you will make the container that will hold the inner fill materials.

You should use materials of high quality to ensure the strength and integrity of the capsule shell.

The main ingredients include:

i. Gelatin

ii. Proprietary polymers

iii. Water

iv. Plasticizers

v. Other ingredients including opacifying agents, color, sweeteners among others.

Heat the ingredients for about 3 hours in a melting tank and they will melt to form molten liquid mass.

With the help of the encapsulation machine, the warm gelatin will flow to the spreader box.

It spreads over a revolving cooling drum that will form ribbons.

The machine has two sides and whatever happens on the left side also happens on the right side.

In the long run, the two gelatin ribbons from both sides will reach the tooling system simultaneously.

Step Two: Formulating the Filling Ingredients

The inner fill materials are the main substances that you will enclose within the capsule coat.

Inner fill materials are in different forms such as liquids, suspensions and semi-solid solutions.

The formulation process of the inner fill materials has to be homogenous to ensure availability of every vital component.

Your choice of equipment and process of formulating fill materials will vary according to the type of ingredients.

The kind of equipment that you may use include:

i. Fluid bed processors

ii. Drums and bins

iii. Hammer Mills

iv. Pharma Ovens

You have to ensure that the inner fill materials follow these criteria:

i. Guarantee the stability of all the ingredients

ii. Increases bioavailability of ingredients

iii. Remains stable for a long period

iv. Ensures the possibility of the filling process

Fill the product tank or the hopper with the fill material.

The fill material flows to the heated injection wedge as it awaits the filling process.

Step Three: Filling the Acid Resistant Caps

At this stage, the left and right ribbon move to the die roller system.

At the same time, the wedge feeds the fill materials to the die cavity.

As the machine cuts and forms the gelatin caps, it also fills them with the fill materials.

Note that this is the stage where the die rolls determine the size and shape of the capsules.

At the same time, the machine will cut and hermetically seal the capsules.

Step Four: Drying the Acid Resistant Softgel Capsules

Drying will remove all the excess moisture from the capsule.

First, you will pass the acid resistant capsules through a tumble dryer.

The tumble dryer removes a quarter of the moisture content of the capsules.

After that, place the capsules on stackable trays and move them to the drying tunnel.

The drying parameters will depend on the moisture content of the capsules.

Two piece acid resistant capsule

Two piece acid resistant capsule

Step One: Preparing the Ingredients

The ingredients that you will use include:

i. Gelatin

ii. Proprietary polymers

iii. Demineralized hot water

iv. Hypromellose

v. Other ingredients including opacifying agents, color, sweeteners among others.

You will omit the plasticizers which often makes the capsules soft.

Instead, you will include hypromellose which will maintain low moisture content of the capsules.

In a jacketed pressure vessel, prepare all the ingredients by stirring until the gelatin dissolves completely.

Apply a vacuum that will remove all the air bubbles in the mixture.

Dispenses aliquots of this mixture to different containers and add dye solutions.

Make sure that you test the viscosity as it will determine the thickness of the capsules.

Step Two: Heating the Mixture of Ingredients

Transfer the mixtures to heated holding hoppers or the encapsulation machine.

The machine has two parts which will make the upper and the lower part on either side.

Most of the machines have around 50,000 mould pins that will assist in molding the caps.

Remember, you have to monitor and control the temperature and humidity of the manufacturing environment.

Step Three: Molding Process of the Caps

From the holding hopper, the molten gelatin flows to the hopper or a dip pan.

Once on the dip pan, the machine dips sets of moulds at room temperature into the gelatin solution.

A film forms by gelling around the surface of the mould pins.

After that, the machine removes the mould pins from the gelatin solution as it rotates them to form uniform thickness.

Step Four: Drying the Gelatin Films

The pins then go through a group of drying kilns which blows large volumes of humidity air over them.

As soon as the films are dry enough, you will remove them and cut them according to the right sizes.

Since the machine has two sides, you will do the same to the other side of the machine.

Join the right and the left cap to form a complete empty capsule.

Remember, capsules are empty so they will have to go through the filling process.

Make sure that the joints are temporary for easy removal and filling before permanent sealing.

Auxiliary Processes for Both Soft and Hard Acid Resistant Capsules

After manufacturing the acid resistant capsules, its now times for additional auxiliary operations.

Quality Control

You will inspect and remove all the capsules that have deformations.

Here, you can use a sorting machine to eliminate any capsule with errors.

The main focus will be on:

i. Eliminating broken, damaged and misshaped capsules.

ii. Conducting a microbiological test

iii. Verify the weight, appearance, and content uniformity of the capsules

iv. Determine the moisture content of the capsule

Polishing and Packaging Acid Resistant capsules

Polishing involves cleaning and removing any material that may be on the surface of the capsules.

Using a capsule printing machine, you can print unique identification codes on the capsules.

The final step is packaging the capsules in readiness for transportation.

Buying Acid Resistant Empty Capsules

SaintyCo is your solution for purchasing acid resistant empty capsules made from hypromellose.

SaintyCo acid resistant capsules

 SaintyCo acid resistant capsules

The acid resistant empty capsules are ideal for a wide range of pharmaceutical applications.

This is because they meet all the quality standards and global regulatory acceptance for physical and chemical tests.

The acid resistant empty capsules comply with the following quality standards:

  • cGMP ensuring the acid resistant capsules are safe and effective.
  • FDA requirements,
  • Pharmacopeia standards such as USP, NF, EP and JP
  • International Standards Organization (ISO) ensuring the products are of the right quality standards.
  • Kosher certified and Halal certified

The cost of the products is competitive and the most favorable in the business.

The cost also varies according to the sizes.

SaintyCo is your trusted supplier for acid resistant capsules of various sizes ranging from 000, 00, 0 to 1, among other sizes.

We are able to supply different customers all over the world through our efficient order and delivery system.

Acid Resistant Vegetarian Capsules Vs Gelatin Acid Resistant Capsules

Acid resistant capsule manufacturers take into account the fact that consumers have different dietary requirements.

· Acid Resistant Vegetarian Capsule

Some of the consumers follow a strict dietary rule with not animal products involved.

Acid resistant vegetarian capsules are meant for the people who follow strict halal rules.

They are also important for people who are allergic to animal products.

The most common types of acid resistant vegetarian capsules are GAR HPMC and GAR pullulan capsules.

The most common ingredient for making the acid resistant vegetarian capsule is tapioca.

· Gelatin Acid Resistant Capsules

Just as the name suggests, acid resistant gelatin capsules have gelatin as the main ingredient of the coat.

Gelatin is an animal product that comes from the hydrolysis of animal skin and bones.

The gelatin acid resistant capsule is suitable for people who are not affected by animal products in their diet.

Quality Standards and Requirements for Acid Resistant Capsules

Acid resistant capsule manufacturers have to meet particular quality standard and requirements.

These standards will ensure that the capsule is effective and safe to use.

It also protects the consumers from unscrupulous dealers who may take advantage of the consumers.

Some of the quality standards that manufacturers and suppliers have to adhere to include:

· European Pharmacopeia

This body concerns with the quantitative and qualitative composition of medicines such as capsules.

It concerns the inspection of raw materials and the process of synthesizing the raw materials to make the capsules.

These regulations cover excipients, substances and any form of preparation for pharmaceutical use.

It also deals with homeopathic stocks and preparations, antibiotics, and radiopharmaceutical preparations.

· USP (United States Pharmacopoeial Convention

This organization sets different standards for strength, identity purity and quality of medicines among other products.

· JP (Japanese Pharmacopeia)

It is a book that contains all the official pharmaceutical standards of Japan.

The book gives the guidelines on the quality of pharmaceuticals in response to science and technology.

· EDQM (European Directorate for Quality Medicine)

This is a directorate that controls the quality of medicine such as capsules in the European Union.

Acid Resistant Capsule Filling Machines & Equipment

The process of making acid resistant capsules depend on the following equipment:

· Acid Resistant Capsule Filling Machine

Acid capsule filling machine is a type of equipment that assists in the filling of acid resistant capsules.

You can use this equipment to fill capsules with pellets, powders, granules, tablets, and liquids.

The process of filling the acid resistant capsules in encapsulation.

Modern encapsulator machines or filling machines have a control panel that allows you to control the speed and size difference.

· Tamping Pin Filling Machine

This equipment has five pins and a dosing disc with multiple holes on the surface.

It has a tamping plate that closes the multiple holes on the surface of the dosing disc.

It works on a principle where the dosing disc rotates as the holes from one tamping pin to the next.

As materials flow into the holes, the machine presses the materials simultaneously.

This results in a slug that flows into the capsules.

You can use tamping pin capsule filling machine to fill powders or pellets.

Tamping pin capsule filling machine

Tamping pin capsule filling machine

· Dosator Capsule Filling Machine

For micro dosing or filling low weight capsules, dosator capsule filling machine is a perfect alternative.

Dosator capsule filling machine

Dosator capsule filling machine

It uses a plunger with a cavity on its tip.

Machine drives the plunger into the powder, compacts, retracts, trims powder and fill in an empty acid resistant capsules.

· Soft Encapsulation Machine

Unlike the tamping pin and dosator capsule filling machines, if you want to fill liquids, then Softgel encapsulation machine will be a viable option.

Softgel encapsulation machine

 Softgel encapsulation machine

Auxiliary Equipment in Acid Resistant Capsules Manufacturing

You will need the following support equipment:

· Gelatin Melting Tank

This is important equipment in the manufacturing process of gelatin acid resistant capsules.

You can use this equipment for the mixing of all the ingredients including gelatin.

· Tumble Dryer

This equipment assists in regulating the moisture content of the acid resistant capsules.

It works by eliminating almost 25% of the moisture content in acid resistant capsules.

· Capsule Inspection and Rejection Machine

This equipment assists in the automatic inspection of acid resistant capsules.

It sorts the capsules out by rejecting any form of capsule that does not fit the right specifications.

· Chilling System

The equipment assists in cooling off the fluid as you prepare it for heat transfer.

The system comprises of a feedback system, frequency drivers, burner and a chiller.

· Drying Trays

You can use the drying trays to assist in transporting the capsules from the tumble dryers to the drying tunnels.

· Capsule Polisher

You can use the Softgel polisher to refine and clean the surface of the capsules.

· Capsule Printing Machine

At times, you may wish to print or label capsules.

In such situations, you will require a capsule printing machine.

· Capsules Packaging

There are many ways of packaging acid resistant capsules.

Some of the most common options include bottle packaging and blister packaging.

Uses of Gastric Acid Resistant Capsules

A capsule that has the ability to pass through the harsh acidic environment has a lot of applications.

Despite the numerous applications, the major uses are:

i. Protecting the lining of the stomach from potential irritating and harming substances.

Stomach irritations can lead to vomiting, nausea, and potential injury to the patient.

ii. The capsules ensure that the active formulations within the capsule reach the right point.

Once it reaches the right point, it dissolves and releases the content to treat the disease.

For instance, medication for treating intestinal disorder must reach the intestine before it dissolves.

It allows the medication inside the capsules to maintain potency and integrity until it gets to the treatment site.


Why should you suffer in silence with stomach irritations in silent?

It is time to finally embrace new technology in capsule formulation.

You can opt for the acid resistant capsules that will ensure that you get the right treatment with minimal complications.

Call your doctor and get a better prescription before ordering for the acid resistant capsules.

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