Title 3: Capsules

Prepared by
Dr Allan (Amooti) AHIKIRIZA (MPS)
Bpharm, Mpharm pharmaceutics

Pharmacy Students' Lecture

 CAPSULES

OBJECTIVES:
1. Define capsules.
2. Uses of capsules
3. Identify types/kinds of capsules.
4. Give advantages and disadvantages of capsules.

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 Definition.

• Capsules are solid dosage forms with hard or

soft gelatine shells, of various shapes and
capacities, containing a single dose of active
ingredient intended for oral administration.

• Types of capsules:
Two main types of capsules are :
1. Hard gelatine capsules
2. Soft (flexible) gelatine capsules.

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 RAW MATERIALS FOR GELATIN CAPSULES

•Raw materials used are similar for both hard and

soft gelatin capsules.
•The first stage of the process is to prepare a gelatine
solution in demineralised water or a mixture of
demineralised water and glycerol.
•Then colourants and preservatives are added to the
process.

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 1.Gelatin

• Is the major component of the capsule.

• Gelatin possesses four essential basic properties:
1. It is non-toxic and widely used in foodstuffs.
2. It is readily soluble in biological fluids at body temperature.
3. It is a good film forming material.
4. As a solution in water or a water-glycerol blend, it undergoes a reversible
phase change from a sol to a gel at temperatures only a few degrees above
ambient.

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 Gelatin continues---

•Gelatin is a substance of natural origin, but does not

occur as such in nature.
•It is prepared by the hydrolysis of collagen which is
the main protein constituent of connective tissues.
• Thus animal bones and skins are the raw materials
for the manufacture.

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 2.Plasticizers

• The walls of hard gelatin capsules are hard and rigid while that of soft gelatin
capsules are soft and flexible.
• The capsule is soft because it contains a large proportion of a plasticizer.
• The plasticizer which is most frequently used is glycerol.
• Others which have been used are sorbitol, propylene glycol, sucrose and acacia.

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 3.Colorants

• The colorants which are used can be of two kinds:

1. soluble dyes or
2. Insoluble pigment
• The soluble dyes are mainly synthetic in origin and by the use of mixtures of dyes;
capsules can be made in all colours of the spectrum.
• The pigments used are of two types:
• (i) Titanium dioxide which is white and is used as an opacifying agent. (used in largest
quantity)
• (ii) The iron oxides; three are used, black, red and yellow.

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 4.Preservatives

• Preservatives are added to the capsules as an in-process aid in order to

prevent micro-biological contamination during manufacture.
• Preservatives mostly used are benzoic acid, parahydroxybenzoic acid ester
and sulphur dioxide.

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 1. Hard Gelatin Capsules

• Hard gelatin capsules are used for administration of particulate solid

medicaments.
• shell is manufactured from gelatin with the addition of suitable
plasticizers, preservatives and colouring agents.
• The shells consist of two parts/sections; body and cap which locks
together after filling.
• The body is longer than the cap and is filled with a particulate solid
(powdered medicament) and the capsule then closed by bringing cap
(over fitting lid) and body together.

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 Hard Gelatin Capsules…

• The hard gelatin capsule is made in a range of eight sizes; from 000, the largest
size which can be swallowed to size 5, which is the smallest.
• Larger sizes are available for use in veterinary medicine.
• Note: when the humidity is low, the capsules become brittle and when the
humidity is too high the capsule become sticky, flaccid and looses their shape.
Storage in high temperature areas can also affect the quality of hard gelatin
capsules.

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Advantages of hard gelatin capsules as a dosage form

1. The taste and odour of unpleasant drugs are readily masked/ obscured.
2. They are attractive in appearance; i.e. they are elegant.
3. They are slippery when moistened and, easy to swallow and administer with
a draught of water.
4. Fewer excipients are required than for tablets.
5. The shells can be made light resistant/pacified (with titanium oxide) or
coloured to give protection from light.

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 Advantages of hard gelatin capsules…
6. They provide rapid and uniform release of medicament in the gastro-
intestinal tract since the contents are usually in fine powder with
freedom or near-freedom from excipients/adjuncts.
7. The shell is rigid and has water content (moisture) which gives
flexibility and very considerable resistance to mechanical stresses.
8. The cap and body of the shells fit well and give substantial protection
of the drug against air and moisture since they are made to very
fine limits.
9. The shells are physiologically inert and easily and quickly digested in
the gastro-intestinal tract.
10. They are easily filled either extemporaneously or in large quantities
commercially.

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 Disadvantages of hard gelatin capsules.

1. May become sticky on storage, because of absorption of moisture and

hence loose their shape and the quality of drug contents affected.
2. Hygroscopic substances should not be dispensed in capsules since they
absorb moisture from the atmosphere.

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 Pharmacopoeial Standards for Hard Shell Capsules

• Hard shell capsules are subject to quality control and measurement standards
similar to those for tablets, i.e.

1. Uniformity of weight
2. Content of active ingredient
3. Uniformity of content
4. Disintegration
5. Dissolution
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2. Soft gelatin capsule (soft elastic or flexible capsules)

• soft gelatin capsules are made from gelatin and water but with the addition of a
polyhydric alcohol, such as glycerol or sorbitol, to make them flexible.
• The contents of soft capsules are usually powders, non-aqueous liquids,
solutions, emulsions, suspensions and pastes.
• The soft capsules are available in different sizes and shapes e.g. round, oval,
oblong or tube.

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 Uses of soft capsules

• Soft capsules are used primarily:-

1. As oral dosage forms to deliver non-aqueous liquid or non-aqueous semi-

liquid medicaments e.g. vitamins A, D and E capsules, cod liver oil,
tetrachloroethylene (TCE).
2. They may also be used rectally and vaginally.
3. They are also widely used in food and cosmetic industries.

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 Advantages of soft gelatin capsules as a dosage form
1. They are suitable for liquid and semi-liquid drugs that cannot be
compressed into tablets. E.g. vitamin preparations such as cod liver
oil, vitamins A, D and E and multiple vitamins, i.e. They permit liquid
drugs to be presented as solid dosage forms.

2. Liquid therapeutic agents with unpleasant tastes and or/colours are

conveniently administered in soft capsules, e.g. sedative,
ethchlorovynol;the anticonvulsant, paramethadione and the
anthelmintics, tetrachloroethylene (TCE).

3. Stability of the drug is enhanced since it is protected from water

and oxygen by a hydrophobic liquid.
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 Advantages of soft gelatin capsules…

5. They give a drug dispersion of high surface area and good

bioavailability when the ingested capsule breaks and drug dissolve
or disperse in a water-miscible or oily liquid to form emulsion.

6.The dose content uniformity of soft gelatin capsule is good because

the product consists of encapsulated solutions or suspensions
which flow readily and homogeneous.

7.Problems encountered when mixing solids and during compression

are avoided.

8.Soft capsule shells may be coloured to provide protection from light,

(e.g. phytomenadione capsules which are brown) or enteric-coated,
when action in the intestine is required. 19
 Disadvantages of soft gelatin capsules

1. They are unsuitable for preparations containing an appreciable amount of a

solvent that either dissolves gelatin (e.g. water) or can diffuse from the
capsule via the moisture in the shell (e.g. alcohol).

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 SPECIAL TYPES OF CAPSULES:

1. Enteric-coated capsules.
• Enteric –coated capsules resist disintegration in the stomach but
break up in the intestine.
• They are used for:-
• Substances that irritate the mucous membrane of the stomach, e.g.
Indomethacin
• Drugs which are destroyed by gastric juice. E.g. erythromycin.
• Drugs that are intended to act in the intestines. e.g. amoebicides and
anthelmintics (TCE)
• The gelatic capsules are covered with cellulose acetate phthalate or
a wax to prevent disintegration in the stomach.

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 2. Sustained Release Capsules

• They are also known as prolonged release, timed release, or Retard

capsules.
• These dosage forms release the active ingredients continuously over
a period of time. (Several hours).

• This way of administration:-

1. Reduces the number of doses per day taken by the patient, i.e. the
patient’s compliance is enhanced.
2. Ensures a more equal blood level of the medicament, i.e. no
fluctuation in drug blood level.
• Each capsule contains plenty of coated and uncoated pellets which
release drug successively.
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 3. Microcapsules

• Microcapsules consist of a solid or liquid core containing one or more drugs

enclosed in a coating usually in the size range 1 to 2000 micrometres.
• Products smaller than this are referred to as nanocapsules.
• The techniques for enclosing very fine particles in individual capsules are
called microencapsulation. The process involves the application of thin
coatings to small particles of solids or droplets of liquids or dispersions, thus
forming microcapsules.

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 microencapsulation

• Methods available include air suspension, coacervation phase

separation, pan coating, spray drying (fluidised bed coating) and
congealing and pan coating.
• Substances suitable as coating materials been used include:
• Water-soluble materials e.g. gelatin and Povidone
• Water-insoluble materials e.g. ethylcellulose, polyamides and
copolymers of lactic and glycolic acids
• Waxes e.g. paraffin wax and fatty acids
• Gastric-resistant materials such as cellacephate.

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 Microecapsulation cont’

• The film thickness can be varied depending on the surface area of the
material to be coated and other physical characteristics of the system.
• The microcapsules may consist of a single particle or clusters of
particles.
• After isolation from the liquid manufacturing vehicle and drying, the
material appears as a free-flowing powder.
• The powder is suitable for formulation as compressed tablets, hard
gelatin capsules, suspensions and other dosage forms.
 APPLICATIONS OF MICROENCAPSULATION

• Microencapsulation is used for-

1. Protection
• Oxygen-sensitive drugs may be more stable when encapsulated,
e.g. Vitamin A palmitate. (enhanced stability)
• Volatilisation of volatile substances is decreased.
2. Separation
• When separately encapsulated, incompatible drugs or liquids and
solids, can be dispensed together.
• Unpleasant tastes and odours can be masked

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 APPLICATION OF MICROENCAPSULATION

3. Controlling Release
• Microencapsulation techniques may be used to apply sustained-
release coatings.
• Hence achieving modified release of a medicament.
• Microcapsules are being used in several types of pharmaceutical
product, particularly sustained release capsules and oral suspensions.

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