Tablet coating lecture Flashcards
What are the reasons for tablet coating?
Protect drug from environment
Improve taste / feel
Hide colour variations in raw materials
Improve appearance
Aid with brand identification / marketing
Help patient with identification / compliance
Improve handleability / friability during packaging etc
Tailor the release of drug
Sugar vs film coating
DRAW TABLE!!
Film Coating Process- what materials does it need
thin film deposition by spray method
Polymer, plasticizer, colourants, solvent
Film coating Process requirements
Suspension preparation – Even mix of powders, no lumps
Gun geometry – Distance of gun to pan, from gun to tablet bed, from gun to gun
Atomizing / Pattern Air – converted to a mist
Pan Pressure – negative in order to provide an isolated environment
Pan Speed – depends on tablet size, shape and tablet load size
Spray Rate – usually between 80 – 150 ml/min/gun
Inlet-Outlet Air Temperature – Inlet is set, outlet is a function of the system
Total Air Volume – related to drying capacity (sensitive to heat and moisture)
Adhesion of particles to the gun surface – has to be clean
Good exhaust facilities to remove dust- and solvent-laden air
Coating Faults
Orange peel, picking, cracking, bridging, colour variation, film chipping, logo attrition, twinning, cratering
Sugar Coating6-step process:
Sealing,
subcoating,
smoothing / grossing,
colouring,
polishing,
printing
Press Coating is used for
Core shell properties
dual release profile
incompatible drugs
Functional Coatings
it is controlled released
Film coated particles applied to a multi-particulate system
Multi-particulates
Extruded / spheronised granulates - produced in modified granulating equipment
Micro particulate drug release MOA
Diffusion: Water enters the interior of the particle, dissolves the drug and the drug solution will diffuse across the polymeric coating.
Erosion: The coating erodes gradually with the time, releasing the drug contained in the pellet.
Osmosis: An osmotic pressure can be built up within the interior of the pellet.
How does the structure of enteric coat determine its function?
They have free –COOH groups on the polymer backbone. Ionisation increases at a pH of 5.2, and does the solubility. The coat dissolves in the small intestine and stays intact in the stomach. E.g Cellulose / polyvinyl / acrylic derivatives
what are the 3 major mechanisms for multiarticulate?
Multi-particulates
Microparticulate drug release MOA: Diffusion, Erosion, Osmosis
Enteric coating: Protect drug / stomach, free -COOH groups , ionisation increases at pH 5.2 > increase in solubility
