Capsules|Hard Gelatin Capsules|Soft Gelatin Capsules

A capsule is a solid unit dosage form in which a medicinal substance is enclosed in a shell. Shell may be made of gelatin or polymer material.

Types of Capsules

There are two types of capsule

•  Hard Gelatin Capsule
• Soft Gelatin Capsule

Hard Gelatin Capsule

Hard gelatin capsules are made of gelatin and are also known as two-piece capsules because the shell consists of two parts which are as follow,

• Cap
• Body

     

Cap 

• Cap is a smaller portion as compared to the body.
• It acts as a lid or lock and covers the upper portion of the body.
• The cap locks with the body and prevents leakage of product from the body.

Body

• The body is a large part and contains medicinal products.
• During filling the drug substance is filled in the body portion.

Composition of Hard Gelatin Capsules

Hard gelatin capsules are manufactured by following ingredients along with gelatin

• Gelatin
• Glycerine 
• Water

Colourants may also be added on requirements or depending upon the formulation.

Source of Gelatin

Gelatin is obtained from

• Connective tissue
• Skin
• Collagen
• Bones

Appearance

Gelatin is available in the following forms,

• Coarse powder
• Fine powder
• Flakes
• Sheets

Manufacturing of Hard Gelatin Shells

• Hard gelatin capsules are manufactured by dipping the pins in a molten solution of gelatin.
• Pins are made of manganese bronze and are attached to the plate. 
• Pins are available in different shapes and diameters.
• The pins used for the manufacturing of the cap are larger in diameter than body pins so that cap can be fitted over the body.

Following steps are involved in manufacturing.

• Dipping
• Removing & Drying
• Trimming
• Joining

Dipping

• It is the first step and in this step, rods are dipped into the molten gelatin.
•  The pins are rotated to stick the solution uniformly.

Removing & Drying

• The pins are then removed from the solution and are dried with air.

Trimming

• The shells are trimmed to the desired length and are separated from the rods.

Joining

• The cap and body are then joined  with each other.

Steps In Filling of Hard Gelatin Capsules

In pharmaceutical industries filling of hard gelatin capsules involve following steps

• Filling
• Sealing/Locking
• Ejection & Metal Detection
• Polishing
• Sorting

Filling

• In the filling step empty hard gelatin shells are filled with powders, granules or pellets depending on the formulation.
• In Pharmaceutical industries, semi-automatic or automatic machines are used for capsule filling.
• The empty shells are placed in one hopper and the product to be filled is placed in the second hopper.
• In automatic capsule filling machines, a rotating wheel attached with plates having holes is used for holding caps and bodies.
• The caps and bodies are separated by the vacuum suction.
• Bodies go into holes of the lower plate and caps in holes of the upper plates.
• Powder, granules or pellets are filled into the body.

Sealing/Locking

• After filling, caps come over the bodies during rotation of the wheel and are sealed or locked to the body with the help of pins.

 Ejection & Metal Detection

• Filled capsules are ejected from cavities with the help of pins that push filled capsules out of the cavities.
• After ejection capsules are transferred to the discharging chute where they pass through a metal detector to separate capsules containing any piece of metal.

Polishing

• Filled capsules are passed through the polisher to clean and polish the shells from outside to remove any powder attached to the outer side of the shells.

Sorting

• After polishing, filled capsules passed over vibratory sifters to separate any loosely locked capsules.
• After that filled capsules pass through a rotating wheel where empty or low weight capsules are separated.

Storage Of Hard Gelatin  Shells

• Empty hard gelatin shells normally have 13-16% moisture.
• Empty hard gelatin shells should be stored in an environment where temperature and humidity are controlled  in the presence of desiccants like silica gel or clay.
• When hard gelatin shells  are stored in dry places they lose moisture and become brittle.
• When these are stored in a humid environment they absorb moisture and become soft.

Capsule Shell Design

Based on the locking pattern of cap and body following are capsule shell designs,

• Snap Fit
• Coni Snap
• Coni Snap Supro

Capsule Shell Size

• Hard gelatin capsules are manufactured in different shapes, size, length and diameter.
• Size of capsule shell decreases from 000 to 5 means  000 is the largest capsule and 5 number shells are the smallest.

Following are the size of the capsule shells.  

Products To Be Filled

Hard gelatin Shells are used for filling of 

• Powder
• Granules
• Pellets

Hard gelatin capsules are not suitable for filling liquid products.

Also Read:

GMP vs cGMP and 21 CFR.

 Soft Gelatin Capsules

• Soft gelatin capsules are used for liquid preparations.

            

Composition

Soft gelatin capsules consist of the following,

• Gelatin
• Sorbitol or Glycerine
• Antimicrobial Preservatives

Moisture content in the soft gelatin capsule is high as compared to the hard gelatin capsule so antimicrobial preservatives are added to prevent microbial growth.

Colourants may also be added depending upon the requirement or formulation.

Manufacturing Procedure

Following methods are used for the preparation of soft gelatin capsules.

• Plate Method
• Rotary Die Method
• Reciprocating Die Method

Plate Method

• In the plate method a mould is used which has two plates, one is the upper plate and the other is lower plate.
• The warm sheet of gelatin is placed over the lower plate.
• The liquid medicament is poured on the gelatin sheet of lower plate.
• Over the filled medicament another sheet of gelatin is placed.
• Pressure is applied from the upper plate which seals both layers containing medicament.
• The filled capsules are removed from the mould.

Rotary Die Method

• In this method, two ribbons of gelatin are formed from liquid gelatin using a rotary die machine.
• Die form pockets in the gelatin ribbon and Liquid medicament is injected inside the pockets.
• These pockets are sealed by pressure and heat.

Reciprocating Die Method

• This method is similar to the rotary die method.
• The only difference is that in this method ribbons of gelatin are passed through vertical dies which open and close to form rows of pockets in gelatin.
• The medicine is filled in pockets, sealed and cut.
• After cutting, capsules fall into the refrigerant tank to prevent sticking with each other.
  

Products to be Filled

Soft gelatin capsules are used for filling of 

• Aromatic Oils
• Vegetable Oils
• Esters
• Ethers
• Organic Acid
• Polysorbate 80

Test For hard & Soft Gelatin Capsules

Following tests are performed for hard and soft gelatin capsules.

• Disintegration Test
• Dissolution Test
• Weight Variation Test
• Content Uniformity Test

Refrences:

1. The Theory & Practice of Industrial Pharmacy.
2. (Leon Lachman)
3. Pharmaceutical Dosage Form and Drug Delivery Systems  ( Ansel`s)
4. Practical Observations & Self Expierence

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