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)
- HPMCP
- 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:
Aqueous
- 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
Organic
- 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
