coating Flashcards
what happens in the film coating process?
droplet formation impingement wetting and spreading coalescence adhesion drying is continuous
what influences droplet formation?
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
how is coating preformed in a perforated coating pan?
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
how is coating done in the fluid bed system?
top spray
bottom spray
tangential spray
what are the critical coating process variables?
- 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
what are the type of defects in a film coat?
- Picking and cratering
- Rough or ‘Orange skin’
- Cracking and splitting •Peeling and flaking
- Bridging
- Pitting
what mechanisms are drugs released by?
diffusion
osmosis
dialysis
erosion
what does the sugar coating process involve?
- 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
what are the common problems in sugar coating?
- Visual defects
- Sugar inversion
- Sticking of coated tablets
what are the BP stds for coated tablets?
- 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
what are the two types of coaters?
(perforated pan and fluid bed coater)
what would be the possible reasons for coating of solid dosage forms?
- 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)
what are the types of coatings available?
- Film coating
- Sugar coating
- Press coating
- Hot melt coating
- Electrostatic coating
what is film coating?
•Depositing a thin polymeric film onto surface of dosage form
what does a formulation of a film coating usually consist of?
–Polymer
–Plasticizer
–Colorant/opacifier
–Vehicles (solvent or suspending liquid