Pharmacy Courses

An Overview of Pharmaceutical Product Coating

Coating is an important part of pharmaceutical product manufacturing. It's increase the patient acceptance and tablet quality also.

Benefits of tablet and granule coating:

  • Improve the visual quality
  • Modifying drug release characteristics
  • Facilitating handling
  • Improve the product stability
  • Mask the unpleasant taste and odor
  • Increasing the ease to swallow by patient

Coating types:

  • Sugar coating
  • Press coating (compressed coating)
  • Film coating: Conventional and Functional
    • Conventional Film coating: Immediate release/ Non-enteric coating
    • Functional Film coating: Delayed release (Enteric coating), Extended release (Sustained release coating)

Sugar Coating:

  • Larger weight gain (30-50%), High degree of elegant, Multi-stage process.
  • Steps:
  • Sealing: Water impermeable polymer (Shellac, CAP)
  • Sub Coating: Bulking agent ( Talc, Calcium carbonate)
  • Smoothing: Sucrose syrup
  • Coloring: Titanium dioxide
  • Polishing: Beeswax, Carnauba wax
  • Printing: Indelible ink

Press Coating:
  • An adhesive coating that allows even small quantities of immediate release powders to be press coated onto controlled release coated dosage form
  • Used mainly to separate chemically incompatible materials 
  • Used in pulsatile drug delivery system (Fast and rate controlled)

Film Coating:
  • Thickness: 20-100 µm
  • 2-3% weight gain only
  • Logo or break line is possible
  • Automatic
  • Usually single stage
  • High adaptability to GMP
  • Control release is possible
  • Materials used: Film formers, Solvents, Plasticizers, Colorants, Opacifier
  • Sophisticated equipments are used

Particular attention must be paid during sugar coating:
  • Hardness
  • Friability
  • Lamination tendency

Problem arise during coating:
  • Chipping
  • Cracking
  • Non-drying
  • Twinning
  • Uneven color
  • Blooming
  • Sweating
  • Picking
  • Twinning
  • Orange peel
  • Chipping
  • Cracking
  • Bridging
  • Peeling

Polymers used in conventional film coating:
  • HPMC
  • HPC
  • HEC
  • MC
  • EC
  • Na-CMC
  • PVP
  • PEG
  • Ethylacrylate methylmethacrylate copolymer

Polymers used in enteric coating:
  • CAP
  • CAT (Cellulose acetate trimellate)
  • PVAP (Polyvinyl acetate phthalate)
  • HPMCAS (Hydroxypropyl methylcellulose acetate succinate)

Factors influence the quality of film coating:
  • Tablet core
  • Coating liquid
  • Solid contents of coating liquid
  • Process drying
  • Spray equipment
  • Spray rate
  • Pan speed

Aqueous vs. Organic film coating:

  • Water is the most common solvent used
  • Non-toxic, No significant safety issue
  • Dry slower
  • Can’t be used for moisture sensitive products
  • Can’t impact on smell and taste

  • Different organic solvents are used
  • Toxic, Significant safety issue
  • Dry faster (due to volatile solvent)
  • Can be used for moisture sensitive products
  • Can impact on smell and taste

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