Tablet coating
Tablet
coating may define as masks tastes/odors/colors
protects drug modify & control drug release identification/brand
recognition/looks better cons: expense bioavailability tablet quality
requirements.
In other word, tablet coating is define as control taste
control release enteric coating - ph dependent release prevent degradation in
stomach protect stomach from irritant drugs target delivery to intestine should
never be crushed controlled dissolution.
Classification of Coating:
1. Suger Coating
2.
Enteric
Coating
3.
Film
Coating :-
a)
Aqueous
Coating
b)
Non-aqueous
Coating
Purpose of coating:
Many solid pharmaceutical dosage mediums are produced with
coatings, either on the external surface of tablets, or on materials
dispensed within gelatin capsules. Coating serves a number of purposes:
Ø Protects
the tablet (or the capsule contents) from stomach acids.
Ø Protects
the stomach lining from aggressive drugs such as enteric coated aspirin.
Ø Provides
a delayed release of the medication.
Ø To
mask the unpleasant taste, odor or color of the drug.
Ø Helps
maintain the shape of the tablet.
Ideally, the tablet should
release the material gradually and the drug should be available for digestion
beyond the stomach. The coating can be specially formulated to regulate how
fast the tablet dissolves and where the active drugs are to be absorbed into
the body after ingestion.
Many factors can affect the
end-use properties of pharmaceutical tablets:
- · Chemical composition
- · Coating process
- · Drying time
- · Storage and environmental monitoring
Pre-dispensing check list for coating
materials:
1. Room cleaning certificate
2.
Equipment
cleaning certificate
3.
Formulation
Order (FO)
4.
Room
temperature
5.
Accessories
Formulation of coating:
Æ Polymeric materials
Æ Solvent
Æ Titanium dioxide
Æ Color
Æ Flavor
Æ Preservative
Æ Plasticizer
Coating Process Design
& Control:
Tablet coating takes place in a
controlled atmosphere inside a perforated rotating drum. Angled baffles fitted
into the drum and air flows inside the drum provide means of mixing the tablet
bed. As a result, the tablets are lifted and turned from the sides into the
centre of the drum, exposing each tablet surface to an even amount of
deposited/sprayed coating.
The liquid spray coating is then
dried onto the tablets by heated air drawn through the tablet bed from an inlet
fan. The air flow is regulated for temperature and volume to provide controlled
drying and extracting rates, and at the same time, maintaining the drum
pressure slightly negative relative to the room in order to provide a
completely isolated process atmosphere for the operator.
Tablet coating equipment may
include spray guns, coating pan, polishing pans, solution tanks, blenders and
mixers, homogenizers, mills, peristaltic pumps, fans, steam jackets, exhaust
and heating pipes, scales and filters. Tablet coating processes may include
sugar coating (any mixtures of purified water, cellulose derivatives,
polyvinyl, gums and sugar) or film coating (purified water, cellulose
derivatives).
The coating process is usually a
batch driven task consisting of the following phases:
·
Batch identification and Recipe selection (film
or sugar coating)
·
Loading/Dispensing (accurate dosing of all
required raw materials)
·
Warming
·
Spraying (application and rolling are carried
out simultaneously)
·
Drying
·
Cooling
·
Unloading
A control system must therefore
provide flexibility in the way in which accurate and repeatable control of the
coating environment is achieved and will include the following features:
·
Precise loop control with set point profile
programming
·
Recipe Management System for easy parameterization
·
Sequential control for complex control
strategies
·
Secure collection of on-line data from the
coating system for
·
analysis and evidence
·
·
Local operator display with clear graphics and
controlled access to parameters
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