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Capsules - Coggle Diagram
Capsules
Advantages of capsules as a solid dosage form
Easy to swallow
due to elegant shape and appearance, thus improving
patient compliance
.
Minimal stress
involved in processing and filling of materials due to capsule contents being
dry powder blends
(usually simple powder mixtures).
Minimal factors involved in capsule formulation =
ease of preparation
of product having the desired release characteristics (rapid, controlled, or modified).
Wide range of acceptable excipients
to choose from to achieve a desired effect, as hard capsule fills can have a wide range of physical properties (e.g. dry solids, nonaqueous solutions).
Raw materials of capsule shells
Gelatin
Disadvantages
Unsuitable for hygroscopic and moisture-labile materials
: Gelatin contains water which can plasticize the film. Physical properties of the shells will change if not stored properly (e.g. When water is lost from the shells, they become brittle and fall apart).
Religious or dietary restrictions
due to the use of animal materials.
Advantages/ Ideal properties
Edible
: digested into non-toxic products
Soluble
at body temperature: capsule shells dissolve easily when ingested
Forms
strong thin films
so that capsule is small, light and doesn't fall apart easily. Film produced is homogeneous, very robust, and can readily withstand mechanical stresses of filling and packaging.
Undergoes gelation at temperatures just above ambient
: gelation = change in state of gelatin from liquid to solid. Therefore, cost effective as it reduces need for high heat or cooling equipment.
Derived from collagen obtained primarily from
bovine bones or porcine skins
Hydroxypropyl methylcellulose (HPMC)
Advantages
Does not contain animal materials, eliminates religious and dietary restrictions.
Does not react with aldehydes or other agents that cause cross-linking of gelatin
Upon dissolution of HPMC shells, rates of dissolution of drug are similar to gelatin shells, and the results are comparable. Bioavailabilty of the drug remains almost unchanged.
Lower moisture content as compared to gelatin shells. Less chance of "melting" or becoming brittle due to poor storage conditions.
Disadvantages
Onset of action is slower
with HPMC shells than gelatin shells, due to the slower rate of diffusion of water through HPMC shell walls.
Rate of gelation
of HPMC is
slower
than that of gelatin's, leading to a
longer manufacturing time
of HPMC shells as compared to gelatin. Thus, manufacture of HPMC shells is
less cost-effective and more expensive
than the manufacture of gelatin shells.
in vivo
Excipient comparison with tablets
Disintegrants in tablets
Powders are
compressed
Powders have
low porosity
Disintegrants absorb water immediately, start to swell and break tablet apart quickly for faster dissolution
Disintegrants in capsules
Powder fills are
soft
Powders have
high porosity
If regular disintegrants for tablets are used, powder fill swells but not enough to break material apart.
Use superdisintegrants instead, which will swell a lot more than disintegrants, breaking apart powders in capsules more effectively than regular disintegrants.