Formulation of Hard Gelatin Capsule
Hard Gelatin Capsules (HGC)
- Hard gelatin capsules are used for enclosing solid medicament or dry powders of drug substance.
- It is also known as dry filled capsule.
- They are less flexible and consist of cap and body. The cap is short while body is long.
- It is available in different sizes, shapes and colours.
- Hard gelatine capsule are hygroscopic in nature.
Primary Ingredients in Hard Gelatin Capsule
Formulation of Hard Gelatin Capsule required the following primary ingredients-
- Gelatin is a tasteless, odourless protein substance which is extracted by boiling the skin, tendons, ligaments, bones of ox and pig.
- There are two types of gelatine: Type A which is produced by acid-catalyzed hydrolysis and Type B which is produced by alkali -catalyzed hydrolysis.
- Due to non toxic nature gelatin is widely used in food industry.
- Gelatin is readily soluble in biological fluid and it also has good film forming properties.
- The molecular weight of gelatin is 15000-250000.
- Plasticizers are additives that increase the plasticity or fluidity of a material.
- It provides structural integrity to the gelatin so the capsule can maintain its shape.
- The amount of plasticizers determines the rubbery texture of the capsule.
- Sorbitol and glycerin are the most commonly used plasticizers in HGC.
- Primary Ingredients in HGC
- Other components of HGC are colouring agents, preservatives such as methyl paraben, lubricants such as stearic acid and surface treatment agents.
- Titanium dioxide (TiO₂) may also be included for opacifying effects.
- Opaque capsules are used to provide protection against light or to conceal the contents.
Parts of Hard Gelatin Capsule
Formulation of Hard Gelatin Capsule
- The major component of HGC is gelatin.
- Gelatin manufacturing involves organic reactions and thus its preparation is a time consuming process and may require many weeks to complete the processing.
- Previously gelatin capsules were fabricated by pharmaceutical manufacturers but currently, capsule shell production is done by third party suppliers.
- Capsule production is an automated operation that begins with solubilizing the dry gelatin with a mixture of plasticizer and purified water.
- The gelatin solution is heated and transferred to a dip pan or pot which holds specific amount of hot gelatin at particular temperature.
- The amount of gelatin in pot is maintained automatically by controlling flow from hopper.
- In this process, stainless steel pins are submersed in the heated gelatin solution to simultaneously form caps and bodies.
- The pins are maintained at 20 – 22°C, whereas the dipping solution is maintained at 50°C in a heated, jacketed dipping pan.
- The length time to cast the film is about 12 sec.
- During production, the thickness of the capsule wall is controlled by the viscosity of the gelatin solution, speed and time of dipping.
- After dipping, pins are elevated and spinned to uniformly distribute the gelatin over the surface to avoid the formation of a bead at the capsule ends.
- This operation is performed until pins are facing upward.
- Blasts of cool air, which dry and solidify the capsules, is the next operation.
- The viscous gelatin is allowed to dry on the pins (about 100 pairs of pins/mould) and when dry these are removed from the pins.
- A series of bronze jaws are used to strip the cap and body capsules from the pins.
- Capsules are rotated on a fixed clamping device to keep them in parts of the place.
- Once the capsules are dry, they are separated from the pins by a set of mechanical jaws.
- The stripped cap and body parts are further trimmed to the required length using stationary knives.
- The stripped cap and body parts are delivered to a collector where they are firmly held together.
- As collector rotate, knives trims shells to the required length.
- After trimming to the right length, the cap and body are aligned concentrically in channels and the two portions are slowly pushed together to join them.
- The joined whole empty capsule is ejected from the machine.
- Empty capsules are polished in pan. Acela-cota pan is used to de-dust and polish.
- Capsules are rubbed with cloth to make surface smooth.
- Capsules are fed under soft rotating brush to make them free from adsorbed particles.
- The capsules moving on conveyor are examined visually for sorting defective units by the automated systems or by inspectors .
- Often capsules are printed before filling operation Printing is done on offer rotary printing machines having capacities of about 7.5 to 8 lakh capsules per hour.
Size of Hard Gelatin Capsules
- Capsule consists of a base or body and a shorter cap, which fits firmly over its body (base).
- Empty HGC are made in a variety of sizes.
- For human use, eight sizes of capsules are available.
- The capacity of capsule varies from 0.13 ml to 28 ml.
- For human use, empty capsules ranging in size from 000 (largest) to 5 (smallest) are used.
- Generally capsules encapsulate ingredients between 65 mg to 1 g.
Shape of Capsules
- The standard HGC come in traditional, symmetrical bullet or cylindrical shapes.
- Capsules are either dot sealed or banded to prevent body and cap separation after filling.
- As an alternative and to achieve other functionalities self-locking capsules are manufactured, for example, coni-snap and snap fit by Park-Davis, Lo-cap as Posilok by Eli Lily and Star-Lok and Lox-It by Scherer.
- Capsule filling is a complex process.
- The HGC can be filled using manual, semi-automatic and automatic capsule filling machines.
- The choice of capsule size and fill weight depends upon the unit dose requirements and the formulation to be filled.
- The product to be encapsulated must be well developed to ensure mass uniformity.
- Manual Filling:
- Punch method:
- In this method precise number and size of capsule to be filled is selected.
- Capsules body and cap is separated. The powder or granules to be filled are taken on a piece of clean paper and filled by holding the capsule body in between thumb and forefinger.
- It is a common technique used by pharmacist but is a slow and laborious.
- Manual Filling:
- Volume fill method: This method is based upon the total amount of drug needed based upon the amount per dose per day and total number of dosing days.
- Tamping method: This method involves compression of contents. The majority of high speed filling machines does capsule filling using tamping method.
- Wax fill method: This method involves traditional steps of melting wax and mixing of the drugs followed by filling the capsules similar to punch method.
- Machine Filing:
- Hand filling of small quantities of capsules is employed for small volume fills for controlled drug substances and to minimize and more readily account for product losses.
- For larger quantities up to 3000 capsules/min, automated capsule filling machines are most commonly used.
- On a small scale, capsules are cleaned individually by rubbing them with a clean gauze or cloth.
- On a commercial large scale, capsule-filling machines are affixed with a cleaning vacuum that removes any extraneous material from the capsule surfaces as they exit the equipment.
- Major defects include
- hard shell formation, cracks, breaks, pinholes or splits,
- loss of integrity, colour variation,
- non-uniformity of appearance, surface spots and
- embedded particles on capsules, non-uniform body and cap, improper fitting,
- false odour, empty capsule, foreign matter inside the capsules, improper filling etc.
- Whereas minor defects are pits, dents, thin area, specks, spots or blemishes, rough surface with adhering spots, improper opacity, etc.
Storage of Hard Gelatin Capsules
- HGC must be protected against excessive heat and humidity.
- Recommended storage conditions for empty HGC are 15 to 25 °C and a relative humidity (RH) of 35-65 %.
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