hard capsules Flashcards
how has hard capsules evolved over time?
gelatine- PEG-hpmc-enteric-pva
what are gelatine for hard capsules made from?
Fibrous protein, made from collagen Triple helix (quaternary structure). H-bonding/weak covalent bonds- animal skin, bones, hide, tendons.
how do you prepare gelatine for hard capsules?
- Size reduction, removal of meat, blood, fat etc
- Hydrolysis, denaturation of quaternary structure (reduce strength)
- Extraction, washing, sterilization
- Drying, size reduction and fractionation
what are gelatine capsules soluble in?
•Soluble in acid environment of stomach•Solution gives suitable viscosity (colloidal solution) with thermally reversible gelation properties•Films are clear, strong, flexible and high gloss
what is the moisture content of gelatine?
Gelatin high moisture content (13-15 % w/w)
what happens if moisture is removed from gelatine capsules?
becomes brital and may break
or due to reaction with aldehyde groups (contents) or UV (cross linking)
what other materials can be used for hard capsuels?
•Hydroxypropylmethylcellulose (HPMC)(3-5 % w/w)
peg
Other materials = methylcellulose, starch, cross-linked dextrane, PVA (polyvinyl alcohol) copolymer (with acrylic acid and methyl methacrylate)
what may be added to hard capsules?
colours- usually for identification plasticisers- makes more flexible dyes or pigments surfactants flavours/sweetners surfactants
what is the most common cell size?
size 3
what does choice of capsule depend on?
tappened powder density
what will interparticular forces give?
-a larger difference between poured and tapped densities-increase in number of taps required to give tightest packing state
what is used to estimate powder flow?
Carr’s compressibility index and Hausner ratio use powder packing data to estimate powder flow
what does the hausner ratio indicate?
value less than 1.25 indicates good flow (= 20% Carr),value greater than 1.5 indicates poor flow (=33% Carr).between 1.25 and 1.5, added glidantnormallyimprovesf low.>1.5 added glidantdoesn’t improve flow
how do you calculate the capsule powder fill?
Capsule fill wt= tapped bulk density of formulation x capsule volume
how do you manufacture two-piece hard capsules?
- stock solution preparede.g. gelatin& additives
- Gelatindissolved (30-40% w/w) in hot (60-70oC) distilled water. Vacuum applied to removed bubbles of air.
- in hot solution, gelatinhydrolyses & viscosity gradually decreases therefore small batches prepared to minimise this
- colourantsadde