Summary
Summary Capsules
- Institution
- University Of East Anglia
Industrial pharmacy - 1st semester Includes bullet points, key diagrams and images
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CapsulesGelatin Capsules
Edible composed of gelatin or starch
Consists of cap and body
Filled with powder or liquid
Sizes:
5=0.13mL
4=0.20mL
3=0.27mL
2=0.37mL
1=0.48mL
0=0.67mL
00=0.95mL
000=1.36mL
Use capsules instead of tablets when the drug: changes polymorph on compression,
degrades on compression or is water sensitive and not easily dry granulated
Hard Gelatin Capsules
Prepared by hydrolysis of collagen from an animal source
Non-toxic, good film former and readily disperses in body fluids
Characterised by viscosity of solution or gel- bloom strength
Based on force required to force a plunger a set distance into a 6.66% solution at 10 oC
High bloom is used for hard gelatin and lower for soft
Colourants
Soluble dyes or insoluble pigments
Pigments- titanium dioxide (white opacifying agent) or iron oxides (black, red or yellow)
Dyes- azo and non-azo or erythrosine (pink)
Manufacture of HGCs
Gelatin solution prepared in hot demineralised water
Moulds (pins) mounted on metal bars and are dipped in the solution
Removed with film of gelatin and rotated for uniform thickness
Passed through series of drying kilns
Stripped off pins and cut to size and 2 halves
Powder Filling of HGCs (Bench Scale)
Either bench or industrial scale
Halves separated and powder spread to fill them
Powder Filling of HGCs (Industrial Scale)
Dependant- uses capsule body to measure the powder, it slow and depends on operators
skill and uniformity of dosing is dependant on powder flow
, Independent- powder hopper feeds it and a dosator is used to fill
the capsules
Formation of the powder plug:
Dosing tube in which there’s a spring loaded piston
Volume of the dosing tube is a measure of the chamber between
the tip of the tube and the bottom of the piston
Volume can be adjusted by moving the position of the piston
Filling Using Dosage Tubes
1. Dose tube plunged into powder bed- powder rises to form a powder plug
2. Dosing tube ruses out of bed
3. Moves over to capsule body and plunger moves down depositing the powder in a shell
4. Dose is determined by the volume of the plug in dosator
Excipients for HGCs
Diluents- starch or lactose (for low dose drugs to aid flow and compression)
Glidants- fumed silicon dioxide (reduced inter-particulate adhesion to improve powder flow)
Lubricants- magnesium sterates (recues adhesion to metals
Drug Release from HGCs
Dissolution of capsule shell
Readily soluble at 37oC but solubility dramatically decreases as temperature drops (insoluble
at 30oC)
(dm/dt)=DA(Cs-C)/h
(dm/dt)-drug dissolution rate
D- diffusion coefficient
Cs- solubility of drug
C- concentration of drug
h- diffusion layer thickness
A- effective surface area
A can be changed by changing the particles size of the powder (larger=dissolve faster)
Same quantity of powder should contain more particles when you reduce the particle size
Potential cause of slow drug release- particle aggregation as decreases A
Tightly packed particles hinders water penetration so slows down wetting of particles
Hydrophobic powders, lubricants and glidants reduce wetting
Unconventional Capsules
Multi-particulate system (via granulation)- for controlled release purpose
Beneficial dissolution properties
Pellets may be used
Liquid or semi-solid filled HGCs
Molten liquid sets
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