Sterility Principles W9 Flashcards
What needs to be sterile
Eye drops
Nasal sprays
Injections
Tablets and capsules dont need to be as go into stomach acidic environment
Creams are the same as the skin is the toughest barrier - just dont apply to broken skin
Sterility
the absence of viable micro-organisms (it is absolute ; all or none).
Sterilisation
the process intended to achieve sterility (eliminate all viable micro-organisms)
Sanitisation
is a basic level of decontamination; it reduces number of harmful micro-organisms
(bioburden) to a safe level.
Sterility assurance level (SAL)
the probability of micro-organisms surviving in a product item after exposure to the sterilisation process.
Importance of sterilisation
Sterilisation is done to kill or remove all microorganisms from the formulations and devices that are intended to be inserted into the body or injected in the blood stream, So needed to be Sterile, such as :
✓ Injections (aqueous, oily or suspensions) and intravenous infusions.
✓ Ophthalmic preparations (eye drops, gels, contact lenses).
✓ Implants.
✓ Irrigations.
✓ Absorbable haemostats and dressings.
✓ Surgical ligatures, sutures, and instruments.
2 approaches for production of sterile products
1.Terminal sterilisation → Sterilisation of the fully assembled product as a last step.
2. Aseptic processing → Sterilisation of raw materials separately and the assembly of the product following aseptic techniques.
Sterilisation methods
Physical -> radiation, filtration, heat sterilisation (steam or dry)
Chemical -> gas sterilisaion
- Heat sterilisation - steam
Most reliable and used
Achieved by gen of steam under pressure at 121-134 degrees
Default = 121 degrees for 15 mins 15 psi
Action = protein denature and hydrolysis of bacterial enzyme
Provides both moisture and heat
Steam provide homogenous heat distribution with penetration power
Uses autoclave
Autoclave cycle:
- Heating stage : air removal and steam admission.
- Holding phase : items are exposed to the sterilising conditions
( heat + pressure + time ) - Cooling stage : pressure release and cooling down.
Autoclave adv
✓Terminal sterilisation process for aqueous solutions or suspensions.
✓Wide safety margin.
✓Kills bacteria and viruses.
Autoclave disadv
Disadvantages:
✓ Only useful for thermostable and moisture-stable products.
✓ Can not be used for products with oily base.
- Heat sterilisation - dry heat
No steam so higher temperatures
Uses hot air ovens
160 degrees for 2hr
170 degrees for 1hr
180 degrees for 30m
Used for:
✓Thermostable dry powder, and oily injections.
✓Glassware and metal instruments.
✓Depyrogenation of glass
Heat sterilisation process:
- Packing the oven:
o Items packaged in Aluminium foil to provide good post sterilisation protection.
o Avoid packing many small items into large tins.
o Screw cap containers should be unscrewed ½ turn to prevent distortion or bursting and tighten soon after cooling.
o Evenly spaced, containers should be sealed, load should be of same size and type. - Heat transfer achieved by convection (fan) and radiation (walls of the oven and shelves).
- Air cooling using HEPA grade air (prevents ingress of organism).
Hot air oven adv
✓Used for substances affected by moisture.
✓Suitable for assembled apparatus e.g., glass syringes.
✓Less damaging to glass and metal equipment than moist heat.
Hot air oven disadv
✓ Drastic conditions are not tolerated by certain packagingmaterial e.g., plastics/rubber
✓ Not suitable for surgical dressings
✓ Does not penetrate as well as moist heat
✓ Natural moisture in fibres vaporises and causes deterioration
- Radiation sterilisation
Achieved by exposing items in the final container (Terminal method) to radiation, such as:
➢ Ionising → - Beam of accelerated electrons (particulate radiation).
- Gamma-rays e.g. cobalt-60 (60CO) as source and X-ray .
➢ Non-ionising → UV-light (260 nm).
Mode of action: microbial DNA damage through the formation of highly reactive radicals.
Aspects of process of radiation sterilisation
o Irradiator - radiation source.
o Sample area - usually sealed area that contains the irradiation.
o Conveyer belt- passing the sample into the sealed area.
Radiation sterilisation adv
✓ Effective against a large number of bacteria, yeasts, moulds and some viruses
✓ Terminal technique
• Used for surgical instruments, sutures, prostheses
• Dry pharmaceutical products (powders)
✓ Highly efficient.
✓ Can be used for thermo-labile products
Radiation sterilisation disadv
✓ Not effective against some viruses.
✓ Cost: Large installation, training, disposal.
✓ Dangerous.
✓ Perceived side effects.
- Filtration sterilisation
Unique method as it
✓ Removes, rather than destroys, micro-organisms.
✓ Removes viable and non-viable particles.
✓ Applicable only for liquids.
Filtered liquid requires aseptic transfer to sterilised containers and closures.
Requires monitoring of filter integrity and final product sterility testing.
Most of bacteria, fungi, and molds have sizes > 0.5µm, therefore filtration using filters with pore size 0.22 µm would be efficient in removing them.
Filtration doesnot remove:
- Viruses.
- Mycoplasms (Form of bacteria with no cell wall).
- some G-ve “stunted forms”
Filter types
- Depth filter - irregular pore size
• Made of asbestos & wood cellulose, sintered glass, sintered ceramic; and not absolutely retentive.
• Multiple layers, trap micro-organisms within structure
• Used alone in restricted circumstances, i.e. for corrosive liquid, viscous fluids and organic solvents. - Screen (membrane) filter - terminal filter
o e.g. cellulose acetate
o Screen filters are absolutely retentive.
o Suitable integrity tests required
o Before use – check for defects
Advantages of filtration sterilisation
✓ Used for thermolabile products.
✓ Removes bacterial dead bodies:
✓ No remnants.
✓ No endotoxins liberated from G-ve.
DisAdvantages of filtration sterilisation
✓ Can not be used for suspensions.
✓ Not a terminal process.
✓ Sterility tests required so 7-14 day delay.
✓ Viruses and mycoplasms not removed.
- Gas sterilisation
Gas chemicals to eliminate microbes
The gases can be
- Alkylating agents: e.g. Ethylene oxide
- Highly reactive compound
- interact with many functional groups
- It is cytotoxic, carcinogenic and mutagenic.
- highly explosive - Oxidising agents e.g. Hydrogen peroxide
- They are highly reactive and toxic compounds through oxidative process.
Steps in process of gas sterilisation
- Air is removed by vacuum.
- Humidity: steam admitted to required relative humidity
- Sterilise
• Ethylene oxide admitted
– Pre-set pressure
– Pre-set time - Aeration of contents of chamber
• Vacuum removal
• Filter air admitted - Total air replacement
Advantages of gas sterilisation
✓ Few materials damaged (Minimal heat, minimal moisture).
✓ Good penetration in porous loads (Will penetrate rubber & plastics).
✓ Effective against all micro-organisms (Bacteria, viruses, moulds).
✓ Effective at relatively low humidity and temperature.
Dis Advantages of gas sterilisation
✓ Can take up to 10 days
✓ Some plastics & nylon wraps must be left open and sealed aseptically after processing
✓ Costs higher than dry/moist heat
✓ Gas is toxic and flammable
