L53 - Tablet Coating and Drug Release

• What are 3 types of tablet coating?

  Film, sugar, press coating.

  
• Why do we coat tablets?

  - Protect from light/moisture.

  
  

  - Mask taste.

  
  

  - Ease of swallowing.

  
  

  - Coloured coats aids identification.

  
  

  - Gives enteric, controlled release properties.

  
• What's the point of sugar coating?

  - Seals core to prevent water entry (eg with shellac/cellulose acetate phthalate).

  
  

  - Smoothes tablet.

  
  

  - Creates rounded profile via CaCO3.

  
  

  - Printing identifies logo/code.
• What does film coating involve?

  - Deposition( by spraying) of a thin film of polyer surrounding the tablet core.

  
  

  - Coating solution/suspension contains a polymer in a suitable liquid w/ other ingredients. eg pigments/plasticisers.
• What happens in tablet coating?

  - Solution sprayed onto rotating mixed tablet bed or fluid bed.

  
  

  - Drying conditions permit solvent removal to leave a thin deposition of coating material aroun each tablet core.
• Describe the difference in appearance between sugar and film coated tablets.

  Sugar= rounded, very polished.

  Film= shape of original core tablet, not as shiny.

  
• Are "break lines" possible for sugar/film coated tablets?

  Possible for film; not for sugar

  
• Does sugar or film coating have a quicker batch coating time?

  Film coating much quicker

  
• List 4 problems with coating.

  - Picking/chipping.

  
  

  - Roughness.

  
  

  - Sticking.

  
  

  - Film cracking/peeling.

  
• What's the role of enteric coating?

  - Prevents acid attacking drugs unstable at low pH.

  
  

  - Protects stomach from irritation.

  
  

  - Facilitates drug absorption for drugs wanting to be absorbed lower in GI tract (intestine).

  
• What is used for enteric coating?

  - pH sensitive polymers. (isoluble at low pH; solubility inceases as pH increases).

  
  

  - Cellulose acetate phthalate.

  
  

  - PVAP.

  
• How do delayed-release tablets work?

  - Drug core coated with delayed release membrane.

  
  

  - Exposure to small intestine pH (6.8) dissolves coating.

  
  

  - Exposed drug-loaded core disintegrates, drug dissolves and is released.

  
• List some typical ingredients found in enteric-coatings.

  - Cellulose acetate phthalate (CAP).

  
  

  - Glyceryl triacetate.

  
  

  - Isopropyl alcohol.

  
  

  - Dichloromethane.

  
  

  - Water.
• How do functional multi-particulate coatings work?

  
  

  What are they used for?

  - Used for controlled/delayed release.

  
  

  - Drug dose divided into 1000s of spherical particles.

  
  

  - Particles filled in sachet, capsule or compressed into a tablet.
• Give some advantages of membrane controlled systems/ multi-particulates.

  - More consistent GI transit than single dose tablet.

  
  

  - Good stability.

  
  

  - Less likely to suffer from "dose dumping".

  
  

  - Good flow properties.

  
  

  - Higher bulk density.

  
  

  - Low hygroscopicity.

  
  

  - Easy to dose.

  
• Give an example of "dose dumping"

  Eg dose precipitates inside stomach if alcohol consumed, decreasing efficacy.
• What are some disadvantages of multi-particulate systems?

  - Hard to control membrane characteristics using film coating.

  
  

  - Hard to retain in upper GI tract

  
• Describe production of Extruded/spheronised granules.

  - Produced in modifying granulating equipment.

  
  

  - Drug granulate extruded through mesh under pressure to form small particles for spheronisation.

  
  

  - Centrifuge.

  
  

  - Use extruder for thin tubing.

  
• List 3 drug release mechanisms from multi-particulates.

  Diffusion- water enters particle interior and dissolution occurs.

  Osmosis- osmotic pressure builds up when water enters pellet, forcing drug sol out.

  Erosion- coating degrades w/time, releasing drug in pellet.

  
• Why should you not chew/crush enteric coated capsules?

  This could damage pellets

  
• Why should you not take enteric coated capsules/tablets with antacids/food?

  - Antacids/food may increase pH of gastric fluid so the coating dissolves in the stomach instead of the small intestine.
• What are Multiple-Unit Pellet Systems (MUPS)?

  - Enteric-coated particles compressed into a tablet.

  
  

  - Polymer coat must be more flexible bc of compression forces applied in tableting process.

  
  

  - Tablets disintegrate in stomach and small particles pass through pyloric sphincter.

  
• Can MUPS be broken/dispersed?

  Yes, as long as particles within are not chewed or crushed.