22 Questions
Which method of sterilisation involves the use of steam?
Steam
What is the purpose of using special clothing (gowns, masks, hair net, gloves) in preparing parenteral formulations?
To ensure sterility
Which type of radiation is used for sterilisation?
Ultraviolet Light
What is the main purpose of using laminar flow hoods placed in special rooms in preparing parenteral formulations?
To ensure sterility
What is the F0 concept used to compare?
Effect of other temperature/time combinations to 121°C for 15 minutes
What does an F0 value of 10 mean in a sterilisation process?
It is equivalent to 10 minutes at 121°C for killing Bacillus stearothermophylus spores
What is the Z value used for in the F0 concept?
To calculate the time required at a specific temperature to ensure an adequate sterility assurance level (SAL)
What is the F0 value at a particular temperature other than 121°C?
The time in minutes required to provide the lethality equivalent to that provided at 121°C for a stated time
What does a sterilisation process with an F0 value of 8 minutes or more indicate according to BP standards?
It indicates potential sterilisation for all micro-organisms
What is the target F0 value used for in the context of sterilisation?
To calculate the time required at a specific temperature for an adequate sterility assurance level
How is the F0 value calculated using the F0 equation?
$F0 = tT1 x 10(T1 - 121)/Z$
What is the basis of an F0 value calculation?
$F0 = tT1 x 10(T1 - 121)/Z$
What does a sterilisation temperature not reaching instantaneously indicate?
It indicates potential sterilisation during heat up and cool down
What type of kinetics is followed by the death of microorganisms during sterilization processes?
First-order kinetics
What is the relationship between log10(Nt) and time (t) when plotting the sterilization kinetics graph?
Straight line
What does the gradient of the straight line in the sterilization kinetics graph represent?
-k
How can the half-life of killing (t1/2) be obtained from the sterilization kinetics graph?
By setting t = t1/2 and Nt = 0.5xN0
What is the decimal reduction time (D) in the context of sterilization kinetics?
The time required to reduce the bioburden by one-tenth of its initial value
What is the formula for calculating the half-life of killing (t1/2)?
$t1/2 = 0.301 / k$
What is the relationship between D values and the initial number of microorganisms?
Independent of the initial number of microorganisms
How does the effect of temperature on D values behave?
Logarithmic relationship
What is the typical range for Z values in the context of bacteria for moist heat sterilization?
6 to 13°C
Study Notes
- Sterilization kinetics is the study of how microorganisms die during sterilization processes.
- The death of microorganisms follows first-order kinetics, similar to radioactive decay or hydrolysis of esters.
- To experimentally determine sterilization kinetics, hold a formulation at a defined temperature for a defined time, plate out a defined volume of suspension on agar plates, incubate, and count the number of colonies/colony forming units (CFU) to calculate the number of viable microorganisms present at each time point.
- Plotting a graph of log10(Nt) against time (t) results in a straight line with an intercept of log10(N0) and a gradient of -k, where k is a specific value for each microorganism at each temperature.
- The half-life of killing (t1/2) can be obtained by setting t = t1/2 and Nt = 0.5xN0, which results in t1/2 = 0.301 / k, and is independent of the initial number of microorganisms.
- The decimal reduction time (D) is the time required to reduce the bioburden by one-tenth of its initial value and can be obtained by setting t = t0.1(D) and Nt = 0.1xN0, which results in D = 1 / k.
- The decimal reduction time (D) is independent of the initial number of microorganisms and is important for predicting the time required to achieve a specific reduction in microbial load.
- D values, which relate to a particular microorganism and temperature, can be used to predict the time it takes to reduce the number of microorganisms to a specific level or by a specific amount.
- The effect of temperature on D values follows a logarithmic relationship, with higher temperatures leading to lower D values due to increased killing rates.
- Z value, defined as the change in temperature required to cause a 10-fold change in the D value, is used to predict the effect of changing temperatures on the rate of kill of microorganisms.
- Z values are specific to a microorganism and temperature and can be used to predict the effect of temperature on sterilization kinetics.
- In the temperature range of 100 to 130°C for moist heat sterilization, Z values tend to be around 6 to 13°C for bacteria of interest.
- The equation for calculating D values at different temperatures using Z values is log D = log (DT10 T2 10 1), where DT10 is the time required to reduce the bioburden by ten-fold at the reference temperature.
Learn about the requirements for parenteral formulations including sterility, particulate material, stability, pH, and osmotic pressure. Understand the importance of sterilization techniques such as aseptic methods, special clothing, and laminar flow hoods in ensuring the safety and efficacy of parenteral preparations.
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