§ Capsules are
dosage form containing unit doses of drugs enclosed in a soluble shell of
gelatin, starch or similar material and intended to be swallowed whole orally.
§ Capsules can
also be defined as dosage form in which gelatin shell used to fill an
individual dose of powdered.
§ Capsules can be
filled with dry material semisolid and liquids that are non-solvents
of gelatin.
§ The basic empty
shells are made from the mixture of gelatin, sugar and water and are clear,
colorless and essentially tasteless.
Components of Gelatin:
§ Gelatin USP is a
product obtained by the partial hydrolysis of collagen obtained from the skin,
white connective tissue and bones of animals.
Characteristic of
Gelatin:
§ Gelatin is
stable in air when dry but it subjects to microbial decomposition when it
becomes moist or when it is maintained in aqueous solution.
§ Soft gelatin
capsules have higher moisture contents than hard gelatin capsules.
§ Hard gelatin
capsules contain 9-12% of moisture.
§ If stored in
highly humid environment, additional moisture is absorbed by the capsules and
they may become distorted and lose their rigid shape.
§ If stored in
highly dried environment, some of moisture present in gelatin capsules may be
lost and the capsules may become brittle and may cramble when
handled.
Advantages of capsules:
§ Capsules may be
used for dispensing solid, semi-solid and liquid drugs.
§ Avoidance of the
contact with the unpleasant odor and flavor of medicines.
§ Easy to swallow.
§ Disintegration
is both satisfactory and reliable.
§ Attractive
dosage form.
§ Shells can be
colored to give protection from light.
§ Shells are
physiologically inert and are easily and quickly digested in GIT.
§ Less adjuncts
are necessary than for tablets.
§ If properly
stored, the shells contain 12-15% of moisture which gives flexibility and
consequently very considerable resistance to mechanical stresses.
Disadvantages of
capsules:
§ Capsules are
expensive than tablets.
§ They cannot be
used for aqueous or alcoholic solutions as they will attack the shell.
§ Salts which are
very readily soluble should not be capsulated as their sudden release
will cause the irritation.
§ Deliquescent or
hygroscopic substances cannot be capsulated.
§ Insoluble
substances such as some bismuth salts are reported to cause formation
of enteroliths when administered in the form of capsules.
Types of gelatin
capsules:
§ There are following
two types of capsules:
1) Soft
gelatin capsules:
·
These are prepared from gelatin to which glycerin
or polyhydric alcohol such as sorbitol has been added to
render the gelatin elastic or plastic like.
·
They may have shape round, oblong, oval, elliptical, tube shape.
·
They may be employed to contain liquids, suspensions, pasty materials, dry
powders.
·
Soft gelatin capsules are useful when it is desirable to seal the medications
within the capsule.
·
Soft gelatin capsules are important to contain drug solutions and liquid drugs.
·
Volatile drugs especially susceptible to deterioration in the presence of air
may be better suited to a soft capsule than to hard capsules.
·
Soft gelatin capsules are easy to swallow by the patient.
·
They are not easily prepared except on a large scale with specialized
equipments. e.g. plate process, rotary die process.
·
Soft gelatin capsules are prepared, filled and sealed in a continuous process
using special equipment.
·
Examples of drugs dispensed in soft gelatin capsule are vitamin
E, digoxin.
Preparation of Soft
gelatin capsule:
·
In the plate process a warmed sheet of plasticized gelatin is placed over a
plate having a number of depressions or molds, the sheet is drawn into these
depressions by applying vacuum.
·
A measured quantity of liquid medicament is poured over it, and then another
sheet of gelatin is placed on it.
·
Over this another plate of mold is placed and the pressure is then applied to
combined plates.
·
The capsules are then simultaneously shaped, filled, sealed and cut into individual
units.
·
In the rotary process filled capsules are produced continuously and
automatically.
·
Two continuous sheets of gelatin are supplied to the two die rolls of the
machine which has a number of matching dies and rotate at the same speed and in
the opposite direction.
·
As the gelatin sheets comes in between the rollers the materials to be filled
in is injected through a metering device.
·
The pressure exerted by the material forces the gelatin sheet to go in the cavities
of the die rolls to form two halves of the capsule and fill them.
·
The heat and pressure exerted by the die rolls seals and cuts out the capsules.
·
The finished capsules are then passed through a series
of naphta baths to remove lubricants and then dried.
·
These rotary die machines can produce 25000 to 30000 capsules per hour.
2) Hard
gelatin capsule:
·
These are formed from gelatin containing sugar and water in appropriate
proportions.
·
Hard gelatin capsules are manufactured in two sections:
·
First one is capsular body and shorter cap.
·
The two parts overlap when joined, with the cap fitting over opened capsular
body.
·
The shells are produced by mechanical dipping of pins or pegs of desired shape
and diameter into a reservoir of melted gelatin mixture, maintained at a
constant temperature to obtain the desired degree of fluidity.
·
Then these pegs overlapped by gelatin are pulled out of gelatin and gelatin is
allowed to dry on pegs, then are removed and shells of required length are
obtained.
·
Usually pegs for caps are slightly large in diameter than for capsule body.
·
Several methods of making capsules distinctive are available. One way is to color
the gelatin.
·
Different colors of caps and bodies present beauty and attraction to patient.
·
Hard gelatin capsules intended for human medicine are manufactured in eight
sizes.
|
Size
|
Capacity
|
|
000
|
1000 mg
|
|
00
|
650 mg
|
|
0
|
520 mg
|
|
1
|
320 mg
|
|
2
|
260 mg
|
|
3
|
195 mg
|
|
4
|
160 mg
|
|
5
|
97 mg
|
·
Hard gelatin capsules are of following types:
i.
Snap FitTM
ii. Coni SnapTM
iii. Coni Snap SuproTM
·
All these types have locking grooves, generally two.
·
Some special techniques used in hard gelatin capsule manufacturing are
a)
Imprinting (a word or company name)
b)
Sealing or banding
c)
Two phase filling (to separate incompatible material in same capsule)
d)
Various coatings etc.
·
After preparation, filling of capsules finishing of capsule is done by:
Ø Salt polishing
Ø Pan polishing
Ø Cloth dusting
Ø Brushing
Packaging
of capsules:
·
Capsules are usually packaged in glass or plastic containers.
·
In some cases, pockets of desicant material are added to container to
prevent the absorption of excessive moisture by capsules.
·
Soft gelatin capsules have greater tendency then the hard gelatin capsules to soften
and adhere to one another, and they must be maintained in a cool, dry place.
·
Should be packaged in well closed container.
·
Should be stored at cool place and low humidity levels.
Hand
operated hard gelatin capsule filling machine:
·
Hand operated and electrically operated machines are in practice for filling
the capsules but for small and quick dispensing hand operated machines are
quite economical.
·
A hand operated machine consists of following parts:
1.
A bed with 200 or 300 holes.
2.
A capsule loading tray.
3.
A powder tray.
4.
A pin plate having 200 or 300 pins corresponding to the number of holes in the
bed but capsule loading tray.
5.
A lever.
6.
A handle.
7.
A plate fitted with rubber top.
·
All parts of the machine are made up of stainless steel.
·
The machines are supplied with additional loading trays, beds, and pin plates
with various diameters of holes so as to fill the desired size of the capsules.
·
These machines are very simple to operate.
Working
·
The empty capsules are filled into loading tray which is then placed over the
bed.
·
By operating the handle, the bodies of the capsules are locked and caps separated
in the loading tray itself which is then removed by operating the lever.
·
The weighed amount of the drug to be filled in the capsules is placed in powder
tray already kept in position over the bed.
·
Spread the powder with the help of a powder spreader so as to fill the bodies
of the capsules uniformly.
·
Collect excess of the powder on the platform of the powder tray.
·
Lower the pin plate and move it downward so as to press the powder in the
bodies.
·
Remove the powder tray and place the caps holding tray in position.
·
Press the caps with the help of plate with rubber top and operate the lever to
unlock the cap and body of the capsules.
·
Remove the loading tray and collect the filled capsules in a tray.
·
With 200 holes machine about 5000 capsules can be filled per hour and with 300
holes machine 7500 capsules can be filled per hour.
·
Since the primar reason of filling the drug in capsules is to avoid
odour and taste of the drug.
·
The whole aim is lost if small amount of drug remains sticking outside the
capsules.
·
Therefore all the capsules must be cleaned by wiping each capsule with
surgical guaze or clean cloth.
·
Since another method is to rotate or shake gently the capsules with granular
sodium chloride contained in a container.
·
Then the sticking sodium chloride is removed by rolling them on the clean cloth
surface.
·
The cleaned capsules may be polished by rolling them in a towel which has been
previously sprinkled by lightly with liquid paraffin.
·
This gives very shine to the capsules.
