Coating

Question 1

Reasons for coating

Answer 1

• Protect ingredients from light and moisture
• Improve organoleptic qualities
• Coloured coatings mask changes in colouration of core and aids identification
• Improves handling characteristics
• Increases mechanical strength and no dusting

Question 2

Ideal coating method

Answer 2

Must comply with pharmacopeia before and after
Avoid abrasions, edges and crowns
Avoid breaking

Question 3

Sugar coating

Answer 3

1. Sealing of core with hydrophobic coat
   Shellac with PVP, Cellulose (or PV), acetate phthalate, acrylates
2. Subcoating
   Smoothing out sharp angles
   Use a mixture of solutions and solids or a suspension
   Sugar; calcium carbonate, talc or gum acacia
   Might increase weight by 50-100%
3. Smoothing
   Application of dilute syrup
   Titanium and iron oxides are popular
4. Polishing
   Beeswax or Carnauba wax
5. Printing
   Methods are manual ladling or automated equipment

Question 4

Film coating (Spray coating)

Answer 4

Spray atomised coating solution evenly across a tablet and allow to dry
Most common method
Logos and break line distinct
Sustained release and gastro resistant

Question 5

Contents

Answer 5

Typically adds 2-3% w/w

• Solvent – Organic, recently water
• Polymer
• Pigments – insoluble pigments as well as solube dyes
• Plasticizers – With low glass transition temperatures (PEG, propylene glycol, glycerol)

Question 6

Coating polymers

Answer 6

1. Celluloses – hydroxypropyl methyl celluloses, hydroxypropyl celluloses, methyl cellulose
2. Vinyl polymers – Polyvinyl alcohol
3. Aminoalkyl methacrylate (Eudragit E)

Question 7

Coating issues with film coating

Answer 7

Coatings may be uneven – fail uniformity of mass or patchy coatings
May be abrasive – chipping or broken
Inadequate drying – tablets may stick together

Question 8

Press coating

Answer 8

A tablet is used as a core for a new tablet

No solvent required and lower interactions between layers

Question 9

Enteric coating

Answer 9

Allows tablet to dissolve in the small intestine rather than stomach

• Protect acid labile drugs from stomach i.e. Omeprazole, pantoprazole
• Protect stomach from irritants I.e. aspirin, prednisolone
• Prevention of nausea
• Onset of action is delayed up to 12 hours

1. Methacrylic acid – methacrylate copolymer
   Targets small intestine and large intestine
2. Cellulose acetate phthalate
   pH specific release (soluble when above 2.5)
   Xenoestrogen effects
   Insulin resistance

Question 10

Sustained release advantages

Answer 10

Reduced frequency of dosing
Increased patient compliance
Increased activity of an API overnight
Targets chronic illnesses with breakthrough issues
May lower side effects due to reduced peak plasma concentration

Question 11

SR disadvantages

Answer 11

Cost per unit much higher and branded only
Some API’s absorbed at specific point of GIT
An overdose poses special problems
Tablets can be very large
May lodge in the oesophagus
Localised high concentration causes irritation
Reversing is an issue

Question 12

Osmotic pump

Answer 12

Semi permeable membrane/coat
Osmotic potential causes water to enter tablet
Pressure forces the API out