Medchem and packaging Flashcards
What is the skin anatomy?
Epidermins: Thin sheet outer layer
Dermis: collagen + elastic tissue + reticular fibers
Subcutaneous tissue
What is the route of drug penetrate the skin?
Surface: drug dissolves + diffuses + releases from vehicle
Partition/diffusion - all the way to the systemic circulation
What are the different type of bases for hydrophobic ointments?
Hydrocarbon bases:
Hard paraffin BP + Yellow and white soft paraffin BP
Immiscible with water and low water absorbing capactiy
Form an occlusive barrier - hydrate and encourage absorption
Not prone to oxidation
Parafffin can be sterilised by dry heat - i.e. eye ointment and many antibiotics
Messy and stain clothing
Absorption base:
absorb water
Water in oil emulsions i.e. lanolin alcohols
less occlusive - increaseing water absorptive power
What is ideal properties of a drug for rectal delivery?
Good solubility and lipophilicity + substantialy unionised at pH 7.5
Slower absorption rate - lower peak plasma conc
Lipophillic durgs best formulated in a hydrophillic suppository base and
What are the advantages of using glass as a packaging material?
Clear Strong Stable + heat resistance Impermeable Resistant to acid Canb e treated to modify the surfaces Hygienic Sterilisable Economic
What are the disadvantages of using glass as a packaging material?
Not maleable or ductile Breakable Difficult to work Attached by alkali Sensitive to mechanical handling Heavy Limited range of colours Transparent to visible light + some UV
What are the properties of glass?
super cooled liquid
Prmary constituesnt of silica and mineral quartz
Pure silica forms glass when heated
Silicon dioxide polymerise with strong covalent bonds - matrix
Great tensile strength
Fragile and not ductile
Thermal resistant - high softening point (1600dec)
Transparaent to visible and some UV
Very resistant to acid but attached by alkali - forms soluble sodium silicates at pH >8
Why is soda (sodium carbonate) added to the glass?
reduces softening point of glass to approx 600 dec
Soda alone reduces chemical resistance - susceptible to degradation
Why is lime added to glass?
Replace some of the sodium ions with calcium and closing up the matrix in the glass
Hence improves chemical resistance
Soda lime glass - sodium ions in the matrix can diffuse out of the glas into aqueous solutions - leaching
Problem for alkali sensitive compounds i.e. alkaloids
Microfractures and separation of flakes of glass
Sodium salts can cause flaking i.e. sodium chloride, bicarbonate, citrate, lactate and gluconate
What are the Pharmacopoeial glass types?
PhEur/USP Type I: Neutral glass (Borosilicate) - parenteral use
PhEur/USP Type II: Soda lime Silica glass - Aq parenteral use where pH is lower than 7 (Surface treated: sulphated or silicon coated)
PhEur/USP Type III: Soda lime Silica - Aq oral, not for parenteral
USP-NP: Soda lime silica - low hydrolytic resistance - non-aq solids for oral use
Special considerations in glass bottles manufacturing.
Glass formation and quality in the furnace
Lubricants for parison graphite based - burned off in Lehr
Quality of tools
Spray outside of bottles “conveyor” lubricants - contamination inside?
Temperature control
Final handling of containers - clean when come out from Lehr
What is vulcanisation?
General term involves compounding of rubber with a variety of additives i.e. curing agent and compressing it in metal moulds at elevated temp
Invovles corss-linking between polyisoprene chains
Improves heat stability of the rubber and its resistance to organic solvents
What are the disadvantages of natural rubber?
High permeability to gas and water Ages rapidly/cracking of surface Poor thermal stability Susceptible to microbial attack Leaches additives - form haze in stored solutions Sorbs some compounds i.e. preservatives
What are the main types of rubber?
Natural Rubber
Tapping the tree Hevea brasiliensis
Highly elastic at room temp
Soluble in a variety of organic solvents
Soft plastic rubers formed by vulcanisation
Synthetic Rubber
Generally more resistant to chemcia nd less permeale to air/water
less inclided to leach
Poor elastic properties
i.e. butyl, halobutul and silicone rubbers
What are the typical ingredients of a rubber formulation?
Elastomer i.e. natural rubber + Rutyl Rubber + EPDM
Curing agent/vulcanising agent: i.e. Sulpur + organic peroxide + high energy radiation (cross link)
Accelerators i.e. complex organic compounds (control curing process)
Activators: i.e. ZnO + Stearic Acid (Activate the accelerator)
Plasticisers i.e. Di-octyl Phthalate + LMW polythene (soften the rubber)
Protecting agents i.e. Waxes + Phenolic compounds (prevent ageing)
Colorants i.e. Inert materials - FeO2 + TiO2 + carbon black
Extender/fillers i.e. Oils + china clay (obtain corect physical properties
What are the typical pharmacopoeial testing for closures?
There are 12 typical tests: Appearance/characters Acidity/alkalinity or pH Change Absorbance Reducing substances Extractable heavy metals Extractable zinc Ammonium Residue on evaporation Volatile sulphides Penetrability Fragmentation Self sealing test dimension i.e. min dia internal seal of stopper vs max neck dia of bottle
What are the typical pharmacopoeial testing for glass?
See Ph Eur: 3.2.1. Glass containers for pharmaceutical use
Type I & II: test A; hydrolytic resistance of the inner surfaces of glass containers
(surface test)
Type I glass containers (to distinguish from type II and type III glass containers) Test B (glass grains test) or test C (etching test)
Type I and type II glass containers where it is necessary to determine whether the high hydrolytic resistance is due to the chemical composition or to the surface treatment Tests A and B, or tests A and C
test B. hydrolytic resistance of glass grains (glass grains test)
test C. to determine whether the containers have been surface-treated (etching test)
What are the major types of plastics?
Thermosets
i.e. bakelite
Freq used for caps and other items - not in direct contact
produced by a condensation reaction
Thermoplastics
consists of linear polymers - addition polymerisation of identical compounds
Do not cross link but aggregates with VDW bonds
What are the main types of polyethylene plastics?
High, medium and low density
Most verstile and useful of all plastics i.e. films, closures and containers
What are the advantages of polyethylene?
Free from additives, impermeable to water, resistance to chem and solvents, translucent and flexible
Increase in density decrease felxibility but increase barrier properties and more heat resistant
What are the disadvantages of polyethylene?
LDP: substantial permeability to atmospheric gases i.e O2
permeability to essential oils - cause swelling
Permeability of organic solvents - labels !!
Tendancy to sorb certain compoudns i.e. preservatives
Liable to stress cracking
What are the advantages of Polypropylene?
Similar to polyethylene
Tertiary carbon - 0.05% antioxidant prevent degradation during MFG
Lightest plastic
Softens at 150deg c - autoclave
better physical strenght than LDP
less inclined to stress cracking and sorption of preservatives
Translucency and permeability to water and atm gases - slightly worse than HDP
What are the properties of Polyvinyl Chloride (PVC)?
UPVC - blister packs and plasticised grades - infusion bags
Good clearity and chmical resistance
High permeability to water vapour
Low metling point - need stabiliser
Poosible leaching of additives i.e. DEHP
More chemically resistant than polyethylene and equivalent sorption
Rigid PVC is less permeabler to gasses than HDP
Plasticised PVC siomilar to polypropylene
What are the disadvantages of PVC?
Much more permeable to water vapour
dissolved by some organic solvents i.e. acetone
poor native thermal stability - soften at 80 dec
stabilisers can increase heat resistance
Leaching hazard posed by the presence of DEHP - extracted by lipophilic materials - blood and alcohol