Capsules Flashcards
(33 cards)
Why are capsules used?
*easier to formulate and manufacture than tablets
*some find easier to swallow
*suitable for drugs needing gastric protection
*suitable for taste masking
What two types of capsules are there?
*Hard Gelatin Capsules (HGC’s)- two piece system cap and body with locking device (indents outside/inside cap)
*Soft Gelatin Capsules (SGC’s)- one piece system
What are examples of advanced capsules?
Pulsatile capsules-
*Pulsincap system- insoluble capsule body with degradable plug (made of hydrophilic polymer). Lag time controlled by plug- pushed away by erosion- pulse of drug released from insoluble capsule
Can be dual drug
*Osmotic system- capsule with semi permeable membrane. Has osmotically active layer at bottom. When ingested, water drawn into layer-swells, pushes drug out of cap
What is the most common capsule material?
Gelatin (hydrolysed collagen)
-stable in air when dry, decomposes when moist
What is a vegetarian alternative to Gelatin?
Starch hydrolysate
Why is Gelatin used?
*non toxic
*readily soluble in biological fluids at body temp
*good film former-strong and flexible
*when cooled, solution>gel
What is the grade of gelatin characterised by?
It’s BLOOM STRENGTH-measure of gel rigidity (cohesive strength of cross-linkage between molecules)
(Definition- the weight in grams required to push a plunger with a set bottom diameter, a set distance into a 6.67% w/w Gelatin gel prepared in water and allowed to cook at 10°C for 16-18h.)
HIGH bloom strength=harder material+more viscous in solution
What can HGC’s be filled with?
*powders
*pellets
*granules
*tablets
*semi-solids/liquids
How are solid HGC’s closed?
-indentations that fit into each other
*Coni- Snap- tapered rim, air vents for air to escape, 6 dimples for pre lock
*Dbcaps- cap covers most of body
How are liquid filled HGC’s closed?
*Gelatin band sealing- dilute solution of Gelatin and colour pigment. Prevents leakage, reduces oxygen permeation
*Hydroalcoholic solvent seal- water/ethanol mixture sprayed on joint between cap and body, plus gentle heating to fuse and seal
What property ensures homogeneity when filled powder capsules?
Each ingredient including API should have a closely matching particle size distribution
Also helps avoid segregation
(Narrow size distribution means powder flow easy to predict)
What size should powder particles be to have excellent flow properties?
> 150 um
What methods are used to fill powders into HGC’s?
-punch filling by hand
- hand operated device
-auger filling
-vibration and/or compression assisted
-dosator
-dosing disk and tamping finger
How is filling of powders into HGC’s carried out by using hand- operated devices?
*empty capsules placed on loading tray
*loading tray placed into filler unit
*capsules rotated so capsule body is in filler unit
*loading tray removed
*top plate lifted to remove caps
*bodies filled
*too plate returned to cap them
How are HGC’s filled with powder using the Auger filling method?
*powder placed in hopper with rotating auger
*auger continuously feeds powder to capsule bodies
*amount of powder fed to bodies depends on: time capsule spends below hopper, rotation spread of auger and screw (auger) design
NOTE- powder bulk density can change over time (affecting fill volume)- adjust auger speed and rotation
How are HGC’s filled with powder using a vibration and/or compression assisted method?
*capsules placed on roasting turntable below powder bowl
*powder bowl has mesh floor
*vibrating device helps powder go through mesh to fill capsule body
NOTE: fill mass depends on rotation speed of turntable and strength of vibration
IF COMPRESSION USED
*capsule body overfilled and compressed by plunger
*scraper removed excess prior to capping
Why use semi solids or liquids to fill HGC’s?
*avoids powder flow issues
*improved fill weight accuracy
*improves solubility and absorption
*for low dose/high potency drugs
What type of semi solids are there?
*thermo-softening mixtures- filled in molten state (pumped and filled) and left to solidify- PEG 4000
*thixotropic mixtures- thin low viscosity by mixing, which form hard masses (high viscosity) upon standing when mixing (shearing) ceases. Filled as fluids, semi solid during storage
*pastes
What type of liquids are filled into HGC’s?
Non aqueous liquids
What method is used to fill semi solids/liquids into HGC’s?
*Piston Filling
-volumetric dosing device
-prevent leakage
-semi solids filled as liquids by either heating or stirring
-after filling, revert to solid state
What property of fluids affects variability of fill volume?
Viscosity
-too low; loss of liquid from splashing during filling
-too high; difficult to pump and problems in transfer from nozzle to cap body
What range of viscosities are acceptable for liquid filling of HGC’s?
0.1-20 Pa.s
What do you have to be careful that an excipient added to liquid filled HGC’s doesn’t effect?
Equilibrium moisture content (EMC)
HGC’s shells contain 13-16%
Too much makes shell brittle
Name 3 differences between HGC’s and SGC’s.
*SGC’s have a plasticised shell, HGC’s do not
*SGC’s are usually filled with non aqueous liquids or suspensions, HGC’s semi solids, solids and non aqueous liquids
*HGC’s are split manufacture- shells made in one operation and filled in other, SGC’s in one operation
