The principle involved in soft gelatin capsule manufacturing is the original Scherer method. In this article, we will discuss how soft gelatin capsules are formulated.
Soft Gelatin Capsule Manufacturing
Soft gelatin capsules are a type of solid oral dosage form that contains a soft and flexible outer shell that is filled with either liquid or semi-solid material. Generally, soft gelatin capsules are used for the delivery of vitamins, nutritional supplements, and medications.Various Components of Soft Gelatin Capsule Shell
a) Gelatinb) Plasticising agents
c) Water
d) Preservative
e) Colorant and/or opacifier
f) Other excipients
Read more - Soft gelatin capsules
What is Soft Gelatin Capsule Made off?
In the formulation of soft gelatin capsule, initially, a formulation of wet mass is prepared which contains gelatin, plasticizers, water, and other excipients as per the requirements.After following it the solution of gelatin is fed into the two drums through a spreader box, at which stage gelatin ribbons are produced.
These two sets of ribbons are then fed between two rotary dies to form pockets, which are lubricated by the mineral oil.
At the same time, the required volume of capsule fill material is dispensed into the forming pocket.
The two halves of the capsule that contains the fill material are sealed by applying heat at a temperature of 37 to 40 °C and pressure.
Then removed from the gelatin ribbon and collected.
After collecting, the capsule is washed to remove any lubricant from the capsule surface.
Before equilibrating the capsule under desired humidity that is 20 to 30% of relative humidity and at a temperature of 21 to 24°C, it is important to dry the capsule to remove circa
60 to 70% w/w of water.
After equilibration, the water content within the capsule shell will be at the desired level.
Read more - Hard Gelatin Capsules | Manufacturing Methods
What is the Manufacturing Process Applicable for Soft Gelatin Capsules?
Plate Process
In the plate process technique mold set is used.A warm sheet of prepared gelatin is placed over the lower plate, and then the liquid is poured into it.
Then the second sheet of gelatin is put in the place very carefully followed by the top plate of the mold.
Then this set is placed under the press where pressure is applied to it to form capsules.
Then washed off the filled capsules with the help of volatile solvents to remove the oil traces from the exterior of the capsules.
The gelatin sheet can be either the same or may be different in color.
Robert P. Scherer perfected the rotary-die process for soft gelatin capsules in 1933.
A rotary-die process is a self-governing unit that is capable of automatically and continuously producing finished capsules from filling material and from a supply of gelatin mass which may be either any liquid, semisolids, or paste that will not dissolve the gelatin.
The machine forms two continuous gelatin ribbons that are bought into the combination between an injection wedge and a pair of revolving dies.
The exact or accurate filling under pressure and sealing of the capsule wall occurs as dual and simultaneous operations; each is elegantly timed against the other.
In the rotary-die process, the content of each capsule is individually measured by a single stroke of a pump so a plunger that is accurately constructed travel of 0.025 in will deliver 1 <minim> (apoth).
The Scherer machine consists of a batch of pumps that are arranged so that many capsules are formed and filled simultaneously.
All pumps are designed in such a way that they are extremely small mechanical tolerances and an extremely high degree of precision and similarity.
Based on weight, all the operations are controlled by actual periodic checks with a group of analytical balances.
The individual net-fill weights of capsules that result from large-scale production may vary which means not more than 3% of the theoretical value, depending upon the type of material used.
Encapsulate viscous materials like ointments and pastes are made possible through the rotary-die process.
In such a way, solids can be milled or ground with a vehicle and filled into capsules.
When there is requirements of a high degree of accuracy and a completely sealed product are required then this form of enclosure is ideally suited.
The requirements for the production of capsules are a modern and well-equipped capsule plant that is to be completely air-conditioned with a high-quality water source.
For the protection of oxidizable substances before encapsulation, the operation includes the availability of carbon dioxide at every exposed step of the operation.
The light damages certain drugs so special ingredients have also been used in the capsule shell to protect it from the light.
A rotary-die process is a self-governing unit that is capable of automatically and continuously producing finished capsules from filling material and from a supply of gelatin mass which may be either any liquid, semisolids, or paste that will not dissolve the gelatin.
The machine forms two continuous gelatin ribbons that are bought into the combination between an injection wedge and a pair of revolving dies.
The exact or accurate filling under pressure and sealing of the capsule wall occurs as dual and simultaneous operations; each is elegantly timed against the other.
In the rotary-die process, the content of each capsule is individually measured by a single stroke of a pump so a plunger that is accurately constructed travel of 0.025 in will deliver 1 <minim> (apoth).
The Scherer machine consists of a batch of pumps that are arranged so that many capsules are formed and filled simultaneously.
All pumps are designed in such a way that they are extremely small mechanical tolerances and an extremely high degree of precision and similarity.
Based on weight, all the operations are controlled by actual periodic checks with a group of analytical balances.
The individual net-fill weights of capsules that result from large-scale production may vary which means not more than 3% of the theoretical value, depending upon the type of material used.
Encapsulate viscous materials like ointments and pastes are made possible through the rotary-die process.
In such a way, solids can be milled or ground with a vehicle and filled into capsules.
When there is requirements of a high degree of accuracy and a completely sealed product are required then this form of enclosure is ideally suited.
The requirements for the production of capsules are a modern and well-equipped capsule plant that is to be completely air-conditioned with a high-quality water source.
For the protection of oxidizable substances before encapsulation, the operation includes the availability of carbon dioxide at every exposed step of the operation.
The light damages certain drugs so special ingredients have also been used in the capsule shell to protect it from the light.
Norton Capsule Machine
This machine formulates capsules automatically with the help of two films of gelatin between a set of vertical dies.As these dies close, open, and close that in effect a continuous vertical plate further forms row after row of pockets over the gelatin film.
Now, these are filled with drugs or medicaments and by processing further through the dies, they are sealed, shaped, and cut out of the film as capsules which are then further dropped into a cooled bath of solvent.
Accogel Capsule Machine (Stern Machine)
The Accogel machine uses the process of rotary dies system.
The uniqueness of this machine is in that it is the only machine that can successfully fill dry powder into a soft gelatin capsule.
With the help of this machine, the capsules can be made in a variety of colors, shapes, and sizes.
Bubble Method for Soft Gelatin Capsule (Seamless Process)
In the seamless process or bubble method the soft gelatin capsules can be produced without the requirement of dies.In this method, a molten gelatin stream runs at a constant rate through an outer nozzle of a concentric tube.
With the help of a pump, the liquid formulation with medicaments is dispensed through the inner orifice.
By a pulsating mechanism, the growing stream is broken up into a steady flow of uniform size that is leading to the formation of droplets covered in molten gelatin.
Finally, the formed capsules were removed quickly from the nozzle, slowly solidify, and ejected automatically from the machine.
Read more - What is the tablet dosage form?
Formulation Consideration During Manufacture of Soft Gelatin Capsules
While manufacturing the soft gelatin capsules there are the following things that should keep in mind of manufactures;Drug Compatibility with Gelatin and Shell Components
The contents that are filled in the soft gelatin capsules can be solids, semi-solids, liquids, or suspensions. So the filling materials should not interact with the gelatin shell and components of the shell.Drug Stability with Moisture Content
The moisture content of soft gelatin capsules is generally higher than that of hard gelatin capsules. Hence, for ensuring the chemical stability of the drug, moisture-sensitive drugs should not be prepared in soft gelatin capsules.Drug Stability at Temperatures 35°C to 40°C
While encapsulation, the fill materials can be heated up to 35°C. So, highly thermolabile drugs can not be encapsulated in soft gelatin capsules.The pH of the Fill Material
Highly acidic as well as basic pH should be avoided because if the pH will below 2.5 then it will lead to hydrolyzed gelatin due to which leakage can occur.If the pH of the filling material will be greater than 9 so, it shows a tanning effect on the gelatin.
Due to the tanning process, crosslinking of gelatin may occur which leads to the hardening of the shell.
The shell is not dissolved in water and is also not digested in the gastrointestinal fluid.
Migration of Drug Substances into the Shells
It is one of the most important conditions of soft gelatin capsule preparation is to ensure that there is minimum interaction between the liquid fill material as well as the capsule shell.The drug materials can migrate into the capsule shell from an oily vehicle, this is related to the water solubility as well as the partition coefficient between nonpolar solvent and water.
I hope you like the article Soft Gelatin Capsule Manufacturing. If you have any questions related to the article feel free to ask in the comments.
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