coating

Question 1

what happens in the film coating process?

Answer 1

droplet formation
impingement
wetting and spreading
coalescence adhesion
drying is continuous

Question 2

what influences droplet formation?

Answer 2

type of nozzle:
pneumatic nozzle- use of compressed gas, usually air to atomize the liquid to small droplets
hydraulic nozzle- droplets are formed when a highly pressurized liquid flowing out of a small nozzle port

movement of the cores
heat
exhaust

Question 3

how is coating preformed in a perforated coating pan?

Answer 3

1- liquid fed and compressed air fed in
2- heated air supplied
3- perforated air in the center of cabinet because of this
4- flows out through exhaust air

Question 4

how is coating done in the fluid bed system?

Answer 4

top spray
bottom spray
tangential spray

Question 5

what are the critical coating process variables?

Answer 5

• Type of equipment
• Equipment dimension & batch size
• Pan or rotor speed
• Method of spraying and spray rate •Atomising air pressure
• Nozzle distance
• Inlet, exhaust and product temperatures
• Drying air volume
• Drying time

Question 6

what are the type of defects in a film coat?

Answer 6

• Picking and cratering
• Rough or ‘Orange skin’
• Cracking and splitting •Peeling and flaking
• Bridging
• Pitting

Question 7

what mechanisms are drugs released by?

Answer 7

diffusion
osmosis
dialysis
erosion

Question 8

what does the sugar coating process involve?

Answer 8

• Involves successive application of sucrose solutions to tablets
• Sealing–To protect tablet from overwetting–Water‐impermeable polymers
• Sub‐coating –To form the typical shape of sugar coated tablets–Syrups with other excipients–Dusting powder
• Smoothing
• Colouring
• Polishing

Question 9

what are the common problems in sugar coating?

Answer 9

• Visual defects
• Sugar inversion
• Sticking of coated tablets

Question 10

what are the BP stds for coated tablets?

Answer 10

• Some similar requirements for uncoated & coated tablets
• But there are differences:
• Film coated tablets must comply with uniformity of weight test •Even for a dose of 2mg/2% or less, where uniformity of content is required
• Disintegration time limit 30 min (film coated tablets) or 60 min (all other immediate release coatings)•Coated tablets are not tested for ‘resistance to crushing’ or ‘friability’, but the cores should be tested in this way
• Special disintegration and/or dissolution test requirements apply of coating are functional

Question 11

what are the two types of coaters?

Answer 11

(perforated pan and fluid bed coater)

Question 12

what would be the possible reasons for coating of solid dosage forms?

Answer 12

• Improve in dosage form stability and protective function
• Masking of unpleasant taste and odour
• Improvement in dosage form appearance
• Ease of swallowing
• Ease of identification
• Ease of handling and packaging
• Modification of drug release (enteric coating, modified release, drug targeting)

Question 13

what are the types of coatings available?

Answer 13

• Film coating
• Sugar coating
• Press coating
• Hot melt coating
• Electrostatic coating

Question 14

what is film coating?

Answer 14

•Depositing a thin polymeric film onto surface of dosage form

Question 15

what does a formulation of a film coating usually consist of?

Answer 15

–Polymer
–Plasticizer
–Colorant/opacifier
–Vehicles (solvent or suspending liquid

Question 16

what are the ideal characteristics of a film coating polymer?

Answer 16

–Solubility
–Viscosity
–Permeability
–Mechanical properties(elasticity, tensile strength and crystalinity etc.)

Question 17

what are the different choices of polymers?

Answer 17

Cellulose derivatives or acrylic polymers and co‐polymers
Non‐functional film forming polymers,
Functional polymers / pH sensitive
Functional polymers / extended release (water insoluble)

Question 18

what is a true latex system?

Answer 18

rue latex–e.g. acrylic polymers and copolymers (EudragitRL and RS)
–Manufactured by an emulsion polymerization process
–Initiate polymerisation by adding an initiator molecule
–Quenching of polymerization process
–Particle size: 50 to 200nm

Question 19

what is a pseudolatex system?

Answer 19

–Prepared from an existing water‐insoluble polymer
–Dissolution of polymer in organic solvent
–Addition of solution to water containing emulsifying agent
–Homogenisation of emulsion
–Evaporation of organic solvent

Question 20

what are the two types of vehicles?

Answer 20

organic solvent and aqueous solvent

Question 21

what are the properties of an organic solvent?

Answer 21

–Wide range of suitable polymers
–Low coating temperature
–Good quality film coating
–Suitable for water‐sensitive materials

Question 22

what are the properties of an aqueous solvent?

Answer 22

–Non‐flammable, non‐toxic, no environmental hazard
–Lengthy processing time
–Limited range of suitable polymers

Question 23

what role do colorant and opacifiers have?

Answer 23

• Contribute to aesthetic appeal of the product
• Product identification
• Water soluble dyes–Sunset yellow, patent blue
• Water insoluble pigments–Aluminium lakes–Titanium dioxide–Iron oxide

Question 24

what do plasticizers do?

Answer 24

• Improve film flexibility
• Reduce film cracking/ brittleness
• Improve adhesion of the film to the surface of the dosage form
• Must show high degree of compatibility with the polymer
• Often chemically similar (e.g. OH‐, COOH‐groups)

Question 25

what is the MOA of a plasticizer?

Answer 25

–Plasticizer molecules interpose themselves between individual polymer strands –Breakdown of polymer‐polymer interaction –Increase opportunity for polymer strands to move past each other –Reduce of glass transition temperature

Question 26

what properties do film formation have?

Answer 26

glass transition temperature crystalline materials amorphous materials transition phase

Question 27

what is a glass transition temperature?

Answer 27

–Transition from the ‘glassy’ into the ‘rubbery’ state –a property of amorphous materials (e.g. polymers) –Glass state = materials are brittle, hard and stiff –Rubbery state = materials are limp and flexible

Question 28

what advantage do crystalline materials have in film formation?

Answer 28

rapid increase in molecular movement when melting point is reached

Question 29

what advantage do amorphous materials have in film formation?

Answer 29

molecular movement increases gradually, whereby the physical properties of the material changes dramatically

Question 30

what influence do plasticizers have on Tg values?

Answer 30

* Effect depends on chemical structure of plasticizer, e.g. ethylcellulose,–M.P. = 175oC; Tg= 129‐133oC * Reduction of Tgof ethyl cellulose when adding plasticizer in a concentration of 25%, –Oleic acid ~45oC–PEG 400 ~70oC * Minimum film forming temperature (MFT)

Question 31

what is MFT?

Answer 31

Minimum film forming temperature (MFT) –Minimum temperature above which film formation takes place –Depends on Tg –Coating temperature should be 10‐20oC above MFT

Question 32

what effect does plasticiser have on contact angle and surface tension?

Answer 32

inc contact angle | decrease surface tension

Question 33

what is the mechanism of film formation for a solution?

Answer 33

* All components of the formulation are dissolved * Rapid evaporation of solvent from both the liquid droplets and the surface of the coated substrate * Increase in polymer concentration and contraction in volume of the coating liquid on the surface of the substrate * Further loss of solvent as solvent diffuses to surface of coating * Concentration of polymer in the coating increases to a point where the polymer molecules become immobile * Final loss of solvent due to diffusion of residual solvent through an essential dry membrane

Question 34

what is the MOA of film formation for an aqueous dispersion?

Answer 34

* Components of coating formulation are present as discrete particles dispersed in the solvent * Droplets adhering to substrate surface lose water due to simultaneous drying * Particles form contacts and capillary forces initiate coalescence * Residual water escapes at very slow rate by diffusion through capillary channels between the particles * Complete coalescence as a result of viscous flow * Coalescence further enhanced by thermal treatment after drying (‘curing)