tablet excipient part ii

GLIDANTS

Added to improve flowability of powders; they improve the flow of granules from the hopper to the dies

Examples

✓ Talc (1-2%)

✓ Colloidal silica (0.2%)

✓ Magnesium stearate (<1%)

✓ Corn Starch (1-3%)

✓ Syloid (0.5-3%)

✓ Aerosil (1-3%) – added to granulation before tableting

✓ Cab-O-Sil (Colloidal silicon dioxide)

LUBRICANTS

Added to ensure the tablet formation and ejection can occur with low friction between the solid and the die wall

Lubricant: two mechanisms

Fluid Lubrication

Boundary Lubrication

Fluid Lubrication

a layer of fluid is located between and separates the moving surfaces of the solid from each other (ex. Liquid paraffin)

Boundary Lubrication

sliding surfaces are separated only by a very thin film of lubricant (ex. Stearic acid and salts at <1% concentration by weight)

Lubricants: effects

✓ Reduce tablet strength

✓ ↑ hydrophobicity – slower disintegration and dissolution

WATER-INSOLUBLE

• Stearates (Mg, Ca, Na)

• Stearic acid

• Sterotex

• Talc

• Waxes

• Stearowet

WATER-SOLUBLE

• Boric acid

• Sodium benzoate

• Sodium chloride

• DL-Leucine

• Carbowax 4000/6000

• Sodium oleate, benzoate, acetate

• SLS / Mg Lauryl Sulfate

lubricants

Add ‘blank’ at the last step prior to compression. Mix for 2-5 minutes

Stearates

most effective lubricants, especially Mg

ANTI-ADHERENT

• Added to reduce adhesion between the powder and punch faces

• Prevents sticking and picking

ANTI-ADHERENT: examples

✓ Talc (1-5%)

✓ Corn Starch (3-10%)

✓ Syloid (0.5-3%)

✓ DL-Leucine (3-10%)

✓ SLS

✓ Metallic stearates

✓ Anti-frictional agent: Mg stearate

improve flowability

Anti-adhesives, Glidants, Lubricants (Anti-frictional Agent) – main function is to ‘blank’

PLASTICIZERS

• Added to produce flexibility and elasticity of the coating and thus provide durability

• Used in film coating

• 20-30% of total tablet weight

• ↑↑ conc. of LMW plasticizers = blushing / spotting

PLASTICIZERS: Examples

✓ Glycerol

✓ Sorbitol

✓ PEG

✓ Propylene Glycol

✓ Diethyl phthalate

✓ Dibutyl subacetate

✓ Castor oil

✓ Triacetin

✓ Citrate esters

OPACIFYING AGENTS

• Added to provide protection to photosensitive APIs

• Ex: Titanium dioxide, water, gelatin

FILM FORMERS

Used in film-coating process to produce smooth, thin films reproducible under conventional coating conditions

FILM FORMERS: examples

✓ Cellulose acetate phthalate (CAP)

✓ Hydroxypropyl methyl cellulose (HPMC)

✓ Hydroxypropyl cellulose

✓ Methyl cellulose

✓ Methacrylate

✓ PVA

✓ PVP

✓ Shellac

Film formers: most used

CAP, methacrylate, PVP, shellac

GLOSSANT

Added to provide luster to the tablets without a separate polishing operation

Examples: Beeswax, Carnauba wax