What Methods are Used for Manufacturing Sustained Release Pills

ID-100181753Controlled release pills (or sustained release or SR) are manufactured in such a way that they release drugs (for absorption) in gastrointestinal tract in a planned and predictable way, which is usually at the rate slower than conventional tablet preparations. Various techniques are used for manufacturing SR pills, such as

  • Coated beads or granules or micro encapsulation: when coating (commonly of starch and sugar) is used in a tablet, the outermost layer left uncoated for immediate release of drug after taking. For the remaining medicine, single to multiple coats (commonly ethylcellulose is used) of varying thickness are used for release of medicine at different time interval. Beads with different thickness dissolve at different time interval and provide sustained and prolonged drug release and drug action, which can not be achieved by conventional pill preparations. Micro-encapsulation is usually done by spray-drying.
  • Embedding drug into slowly dissolving matrix: in this technique the drug (for sustained release/action) is combined with lipid or cellulose like material and made into granules, which are than made into tablet or capsule. The combined drug is released slowly when it comes in contact with body fluid (gastro-intestinal secretions). Some drug is added without combining with lipid or cellulose like material for immediate release/effect.
  • Embedding drug into inner material: in this technique drug is granulated with inert plastic matrix such as polyethelyne, polyvinyl acetate etc. and made into tablet. Some amount of drug is not mixed with inert plastic material for immediate release/action. The drug is slowly released after it comes in contact with gastrointestinal fluid (including gastric acid) leaving behind the inert plastic insoluble material, which is passed with the feces.
  • Hydrodynamically balanced drug delivery system (HBS): when a tablet/capsule is manufactured using HBS, the tablet/capsule upon contact with gastric fluid forms a complex which is lighter than the gastric fluid and it floats. When the cover of the pill is dissolved, the outermost layer comes in contact with gastric fluid and swells and forms a barrier that prevent immediate penetration of gastric fluid into the pill and prevent release of drug and immediate absorption. When the outermost layer erodes the drug present there is released and the next layer of boundary is formed, which also slowly erodes and this process continues as long as drug action is desired.

There are also various other techniques used for manufacturing of controlled release (sustained release) medicine preparations, such as occuserts for eye, subdermal implants, osmotic pump etc.

“Image courtesy of┬áNaypong / FreeDigitalPhotos.net”.

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