Applications of capsule:
1. Enteric coated capsule: These capsules do not disintegrate in stomach (Acidic Medium) but break up in intestine (Alkaline medium). On commercial scale, a coating of cellacephate (cellulose acetate phosphate) and mixture of waxes with fatty acids and esters are given.
Categories of drug needed coatings:
Irritation to GIT
Destroyed in GIT
Specially intended to intestine
Required to produce delayed action
2. Sustained release capsule:
In order to maintain a proper blood concentration.
Preparation of coated pellets according to different release rate.
E.g. a capsule may be filled with mixture containing 30 % uncoated pellets for immediate release of the drug, 30 % each of the coated pellet, that release the drug 4 hour and 8 hour intervals and 10 % of neutral pellets are mainly used to fill capsule.
3. Rectal Capsule:
Soft gelatine capsule may be used as substitutes for rectal and vaginal suppositories.
Soft gelatine capsule of various shapes and sizes available but pear shape commonly used.
Both solid and liquid medicament can be filled in to soft gelatine capsule.
Also base used for incorporating medicament is non toxic, non-irritant and compatible with capsule shell.
4. Capsule containing ophthalmic ointments
It must be sterile
It required to fill in single dose container
Soft gelatine commonly used
Capsule punctured by using sterile needle and then instilled into the eye.