coating Flashcards
what is coating
It is the application of a coating material to the exterior of a
tablet with the intention of achieving benefits and properties
to the dosage form over the uncoated ones.
why do we use coating
- Extend shelf life by protection of the ingredients from the
environment (light, moisture and oxidation). - Coating provides an efficient sealing of the tablet cores as a
method of taste masking for drugs that have bitter or
unpleasant taste, or unpleasant odor. - Tablets that are coated are somewhat easier to swallow than
uncoated tablets (significant for large tablets). - Coloured coatings mask any batch differences in the
appearance of raw materials (patient concern). - Coloured coatings aid in the rapid identification of product
by the manufacturer, dispensing pharmacist and patient. - Coating tablets facilitates their handling on high speed
automatic filling and packaging equipment (as a result of
improved product flow and mechanical strength). - Cross contamination is also reduced in the manufacturing
plant, as ‘dusting’ from tablets is eliminated by coating. - Functional film coatings are used to impart modified release
properties to the coated tablet. - Coatings may be optimized with respect to colouration and
gloss to aid in their sales appeal. - Avoid chemical incompatibilities by incorporating another
drug in the coa
what are the types of coating
- Film coating
- Sugar coating
- Compression coating
what is film coating
Film coating is the more contemporary and thus commonly
used process for coating oral solid dosage forms.
First introduced to the pharmaceutical industry in the 1950’s
Nowadays all newly launched coated products are film
coated rather than sugar coated
what are the different types of film coating
- Immediate release film coating (also known as non-functional
coating): the coating has no measurable effect of
biopharmaceutical properties. This coating is readily soluble in
water. Thus, the coating is mainly used to provide improved
appearance, taste-making and/or identification to the tablets. - Modified release film coating (also known as functional
coating): maybe further categorized as either delayed release
(e.g. enteric or gastro-resistant coating) or extended release
coating (i.e. sustained, prolonged, controlled release coating).
what is gastro-resistant coating (delayed release )
are only soluble in water at pH values
grated than 5-6. Therefore they are either used:
1. to protect the drug while the tablet is in the stomach, in the
case of acid labile drugs
2. Or to prevent drug release in the stomach, in the case of drug
that are gastric irritant
what is extended release coating
are mainly insoluble in water. They are
designed to ensure that the drug is release over a relatively long
period time (typically 6-12 hours). Extended release formulations
reduce the number of doses a patient needs to take throughout
the day and often improve drug efficacy
what is film coating
a process in which polymer –
based coatings are applied on the surface of drug-containing
dosage units (either tablets, pellets, granules, capsules or drug
powders and crystals).
Such coating is thin (in the range of 20 - 200μm).
The dosage unit on which the coating is applied is defined
core.
The coating liquid (solution or suspension) contains a polymer in
a suitable liquid medium in addition to pigments and plasticizers.
1. This liquid is sprayed (i.e. atomized) on to a rotating, mixed
tablet bed or fluid bed.
2. The drying conditions permit the removal of the solvents so as
to leave a thin deposition of coating material around each
tablet core.
what are the basic requirements for any film coating equipment
- Adequate atomization (conversion into very fine droplets) of
the spray liquid for application to the tablet cores. - Adequate mixing and agitation of the tablet bed. Spray
coating relies upon each tablet passing through the area of
spraying. - Sufficient energy input in the form of heated air to evaporate
the solvent. - Good exhaust facilities to remove dust and air carrying the
evaporated solvents
what are the two different film coating equipment
- Side-vented coating pans
- Fluid bed
what is the side vented coating pan
Also called perforated coated pan. These equipments consist of
perforated or partially perforated drums that are rotated on their
horizontal axis.
Baffles are often placed in the coating pans to facilitate tablets
tumbling within the pan for a more uniform film distribution.
Some designs include: Accela Cota, Glatt coater, Driacoater.
what is unique about accela cota side vented coating pan
Air is directed into the drum, is passed through the tablet bed and
is exhausted through the perforations in the drum
what is unique about glatt side vented coating pan
Similar technology to the
Accella Cota
Here, the horizontal process air
flow minimises turbulence in the
spray nozzle area and therefore
contributes to improved
coating result
what is unique about driacoater side vented coating pan
It introduces drying air through hollow
perforated ribs located on the inside
periphery of the drum. The ribs dip
into the bed as the pan rotates.
Drying-air passes through the tablet
bed.
Exhaust is from the back of the pan.
what is the fluid bed dryer
Fluidized bed coaters function by suspending a bed or a
column of solid particles in a moving gas stream.
A fluidized bed occurs when a quantity of solid particles are
placed under appropriate conditions to cause the mixture to
behave as a fluid. This is typically done by forcing pressurized
air, through the bed of solid particles. This causes the solid
particles (e.g. powders or tablets) to acquire properties and
attributes similar to those of normal fluids, resulting in what is
known as fluidization.
what is the fluid bed dryer
Fluidized bed coaters function by suspending a bed or a
column of solid particles in a moving gas stream.
A fluidized bed occurs when a quantity of solid particles are
placed under appropriate conditions to cause the mixture to
behave as a fluid. This is typically done by forcing pressurized
air, through the bed of solid particles. This causes the solid
particles (e.g. powders or tablets) to acquire properties and
attributes similar to those of normal fluids, resulting in what is
known as fluidization.
what are the different patterns for fluid bed dryers
Top spray.
Bottom spray.
Tangential spray
what is top spray
The spraying nozzle is located on top of the
product chamber. The liquid is sprayed in the
opposite direction to material motion.
If the spray formulation contains a volatile
solvent, evaporation of this solvent from the
spray droplets occur.
The top-spray coating method is particularly
recommended for taste masking on particles
(less used for tablets).
what is bottom spray
Also called Wurster process.
The material (e.g. tablets) to be coated are fed into a
vertical column (Wurster column).
The air that enters from the bottom of the column. The
tablets move upwards and rotate.
As the coating solution enters the system from the bottom,
it is rapidly applied to the suspended, rotating solids with
rounding coats being applied in less than an hour.
The airflow is controlled so that more air enters the center
of the column. The movement of the tablets is upward
through the center of the chamber. They then fall toward
the chamber wall and move downward to re-enter the air
stream at the bottom of the chamber.
Bottom-spray method is recommended for sustained-release
and enteric-release products (for tablets and pellets).
The most commonly known fluid-bed process for coating in the
pharmaceutical industry.
what is tangential spray
The spray nozzle is located on the side of the
product bed. Liquid is sprayed in a tangential
pattern while the materials are in motion.
Here, the bottom plate is not perforated (as in
other fluid bed designs). The bottom disk rotates.
A gap is present between the chamber wall and
the rotating disk. Air flows from the bottom
through this gap.
The disk motion together with that introduced by
the fluidizing air and the gravitational force
cause the materials to move in rope-like motion.
The tangential method is mainly used for sustained-release
and enteric coated products (for pellets).
The high kinetic energy in this equipment is generally
destructive for larger and non-spherical products (i.e. tablets).
what do we add to the tablet when we film coat it
Solvent
Polymer
Plasticizer
Colourants
what do we add to the tablet when we film coat it
Solvent
Polymer
Plasticizer
Colourants
what properties should we consider when we film coat
- Solubility
The functionality of the final coating (e.g. taste masking or modified
release) depends on the solubility of the polymer chosen:
polymers soluble in aqueous fluids (i.e. GI fluids) should be chosen
for non-functional coatings of immediate release products.
polymers with limited or no solubility must be chosen for coating
to provide modified release (i.e. in this case the coating must act
as a barrier to liquid penetration into the tablet). - Mechanical properties
Upon deposition and drying on the surface of the tablet, the
polymer should form a film:
of good strength: in order to resist the mechanical stresses
during coating and tablet handling;
of good flexibility: in order to minimize film cracking during
handling and storage;
of good adhesiveness: in order to ensure that the coating
remains adherent to the surface of the tablets right up to the
point of being taken by the patient.
