excipients in tablets

name the types of excipients found in tablets

• diluents

• disintegrants

• lubricants and glidants

what are diluents

bulking agents

• inert substances added to increase bulk and make tablet practical size for compression

why are hydrophilic diluents needed for insoluble drugs

to help improve wettability and dissolution upon administration

true or false: diluents must have good compatibility with drug

true

name 3 examples of common diluents used for tablets

• lactose monohydrate

• microcrystalline cellulose

• dicalcium phosphate dihydrate

if they drug is incompatible with lactose due to amine groups, which diluent could be used instead

• microcrystalline cellulose

• mannitol

• starch

• calcium sulphate

what is the main function of disintegrants

to facilitate the break up of tablets into individual granules/particles upon water contact

how do disintegrants help break up tablets

• wicking - capillary forces promoting rapid water uptake

• swelling

• release of gases upon contact with water

• melting at body temp

• enzymatic destruction of binder

give examples of general disintegrants

• starches (corn, pre-gelatinised)

• alginates

give examples of super disintegrants

• croscarmellose sodium

• sodium starch glycolate

• crospovidone

what is the difference between general and super disintegrants

general:

• mainly work by wicking or swelling

• less effective

• used at higher levels (5-15%)

super:

• work faster

• more effective

• work at lower concentrations (2-5%)

• enhanced swelling or rapid wicking

when is a disintegrant added

• prior to granulation or

• 2/3 prior to granulation and 1/3 to the dry granules

what is role of lubricant

to reduce friction between powder and tableting tools

e.g. Mg stearate

what is role of glidants

to improve powder flowability e.g. colloidal silicon dioxide

what problem can over-lubrication cause

soft tablets and dissolution issue

why must lubrication be done under low shear for short time

to avoid over-coating particles with lubricant, which decreases bonding

what problem does under-lubrication cause

sticking and picking